Fixed #22603 -- Reorganized classes in django.db.backends.

django/contrib/gis/db/backends/base/features.py

@@ -0,0 +1,82 @@
+from functools import partial
+
+
+class BaseSpatialFeatures(object):
+    gis_enabled = True
+
+    # Does the database contain a SpatialRefSys model to store SRID information?
+    has_spatialrefsys_table = True
+
+    # Does the backend support the django.contrib.gis.utils.add_srs_entry() utility?
+    supports_add_srs_entry = True
+    # Does the backend introspect GeometryField to its subtypes?
+    supports_geometry_field_introspection = True
+
+    # Reference implementation of 3D functions is:
+    # http://postgis.net/docs/PostGIS_Special_Functions_Index.html#PostGIS_3D_Functions
+    supports_3d_functions = False
+    # Does the database support SRID transform operations?
+    supports_transform = True
+    # Do geometric relationship operations operate on real shapes (or only on bounding boxes)?
+    supports_real_shape_operations = True
+    # Can geometry fields be null?
+    supports_null_geometries = True
+    # Can the `distance` GeoQuerySet method be applied on geodetic coordinate systems?
+    supports_distance_geodetic = True
+    # Is the database able to count vertices on polygons (with `num_points`)?
+    supports_num_points_poly = True
+
+    # The following properties indicate if the database backend support
+    # certain lookups (dwithin, left and right, relate, ...)
+    supports_distances_lookups = True
+    supports_left_right_lookups = False
+
+    @property
+    def supports_bbcontains_lookup(self):
+        return 'bbcontains' in self.connection.ops.gis_operators
+
+    @property
+    def supports_contained_lookup(self):
+        return 'contained' in self.connection.ops.gis_operators
+
+    @property
+    def supports_dwithin_lookup(self):
+        return 'dwithin' in self.connection.ops.gis_operators
+
+    @property
+    def supports_relate_lookup(self):
+        return 'relate' in self.connection.ops.gis_operators
+
+    # For each of those methods, the class will have a property named
+    # `has_<name>_method` (defined in __init__) which accesses connection.ops
+    # to determine GIS method availability.
+    geoqueryset_methods = (
+        'area', 'centroid', 'difference', 'distance', 'distance_spheroid',
+        'envelope', 'force_rhr', 'geohash', 'gml', 'intersection', 'kml',
+        'length', 'num_geom', 'perimeter', 'point_on_surface', 'reverse',
+        'scale', 'snap_to_grid', 'svg', 'sym_difference', 'transform',
+        'translate', 'union', 'unionagg',
+    )
+
+    # Specifies whether the Collect and Extent aggregates are supported by the database
+    @property
+    def supports_collect_aggr(self):
+        return 'Collect' in self.connection.ops.valid_aggregates
+
+    @property
+    def supports_extent_aggr(self):
+        return 'Extent' in self.connection.ops.valid_aggregates
+
+    @property
+    def supports_make_line_aggr(self):
+        return 'MakeLine' in self.connection.ops.valid_aggregates
+
+    def __init__(self, *args):
+        super(BaseSpatialFeatures, self).__init__(*args)
+        for method in self.geoqueryset_methods:
+            # Add dynamically properties for each GQS method, e.g. has_force_rhr_method, etc.
+            setattr(self.__class__, 'has_%s_method' % method,
+                    property(partial(BaseSpatialFeatures.has_ops_method, method=method)))
+
+    def has_ops_method(self, method):
+        return getattr(self.connection.ops, method, False)

django/contrib/gis/db/backends/base.py → django/contrib/gis/db/backends/base/models.py

@@ -1,8 +1,3 @@
-"""
-Base/mixin classes for the spatial backend database operations and the
-`<Backend>SpatialRefSys` model.
-"""
-from functools import partial
 import re
 
 from django.contrib.gis import gdal
@@ -10,203 +5,6 @@ from django.utils import six
 from django.utils.encoding import python_2_unicode_compatible
 
 
-class BaseSpatialFeatures(object):
-    gis_enabled = True
-
-    # Does the database contain a SpatialRefSys model to store SRID information?
-    has_spatialrefsys_table = True
-
-    # Does the backend support the django.contrib.gis.utils.add_srs_entry() utility?
-    supports_add_srs_entry = True
-    # Does the backend introspect GeometryField to its subtypes?
-    supports_geometry_field_introspection = True
-
-    # Reference implementation of 3D functions is:
-    # http://postgis.net/docs/PostGIS_Special_Functions_Index.html#PostGIS_3D_Functions
-    supports_3d_functions = False
-    # Does the database support SRID transform operations?
-    supports_transform = True
-    # Do geometric relationship operations operate on real shapes (or only on bounding boxes)?
-    supports_real_shape_operations = True
-    # Can geometry fields be null?
-    supports_null_geometries = True
-    # Can the `distance` GeoQuerySet method be applied on geodetic coordinate systems?
-    supports_distance_geodetic = True
-    # Is the database able to count vertices on polygons (with `num_points`)?
-    supports_num_points_poly = True
-
-    # The following properties indicate if the database backend support
-    # certain lookups (dwithin, left and right, relate, ...)
-    supports_distances_lookups = True
-    supports_left_right_lookups = False
-
-    @property
-    def supports_bbcontains_lookup(self):
-        return 'bbcontains' in self.connection.ops.gis_operators
-
-    @property
-    def supports_contained_lookup(self):
-        return 'contained' in self.connection.ops.gis_operators
-
-    @property
-    def supports_dwithin_lookup(self):
-        return 'dwithin' in self.connection.ops.gis_operators
-
-    @property
-    def supports_relate_lookup(self):
-        return 'relate' in self.connection.ops.gis_operators
-
-    # For each of those methods, the class will have a property named
-    # `has_<name>_method` (defined in __init__) which accesses connection.ops
-    # to determine GIS method availability.
-    geoqueryset_methods = (
-        'area', 'centroid', 'difference', 'distance', 'distance_spheroid',
-        'envelope', 'force_rhr', 'geohash', 'gml', 'intersection', 'kml',
-        'length', 'num_geom', 'perimeter', 'point_on_surface', 'reverse',
-        'scale', 'snap_to_grid', 'svg', 'sym_difference', 'transform',
-        'translate', 'union', 'unionagg',
-    )
-
-    # Specifies whether the Collect and Extent aggregates are supported by the database
-    @property
-    def supports_collect_aggr(self):
-        return 'Collect' in self.connection.ops.valid_aggregates
-
-    @property
-    def supports_extent_aggr(self):
-        return 'Extent' in self.connection.ops.valid_aggregates
-
-    @property
-    def supports_make_line_aggr(self):
-        return 'MakeLine' in self.connection.ops.valid_aggregates
-
-    def __init__(self, *args):
-        super(BaseSpatialFeatures, self).__init__(*args)
-        for method in self.geoqueryset_methods:
-            # Add dynamically properties for each GQS method, e.g. has_force_rhr_method, etc.
-            setattr(self.__class__, 'has_%s_method' % method,
-                    property(partial(BaseSpatialFeatures.has_ops_method, method=method)))
-
-    def has_ops_method(self, method):
-        return getattr(self.connection.ops, method, False)
-
-
-class BaseSpatialOperations(object):
-    """
-    This module holds the base `BaseSpatialBackend` object, which is
-    instantiated by each spatial database backend with the features
-    it has.
-    """
-    truncate_params = {}
-
-    # Quick booleans for the type of this spatial backend, and
-    # an attribute for the spatial database version tuple (if applicable)
-    postgis = False
-    spatialite = False
-    mysql = False
-    oracle = False
-    spatial_version = None
-
-    # How the geometry column should be selected.
-    select = None
-
-    # Does the spatial database have a geometry or geography type?
-    geography = False
-    geometry = False
-
-    area = False
-    centroid = False
-    difference = False
-    distance = False
-    distance_sphere = False
-    distance_spheroid = False
-    envelope = False
-    force_rhr = False
-    mem_size = False
-    bounding_circle = False
-    num_geom = False
-    num_points = False
-    perimeter = False
-    perimeter3d = False
-    point_on_surface = False
-    polygonize = False
-    reverse = False
-    scale = False
-    snap_to_grid = False
-    sym_difference = False
-    transform = False
-    translate = False
-    union = False
-
-    # Aggregates
-    collect = False
-    extent = False
-    extent3d = False
-    make_line = False
-    unionagg = False
-
-    # Serialization
-    geohash = False
-    geojson = False
-    gml = False
-    kml = False
-    svg = False
-
-    # Constructors
-    from_text = False
-    from_wkb = False
-
-    # Default conversion functions for aggregates; will be overridden if implemented
-    # for the spatial backend.
-    def convert_extent(self, box, srid):
-        raise NotImplementedError('Aggregate extent not implemented for this spatial backend.')
-
-    def convert_extent3d(self, box, srid):
-        raise NotImplementedError('Aggregate 3D extent not implemented for this spatial backend.')
-
-    def convert_geom(self, geom_val, geom_field):
-        raise NotImplementedError('Aggregate method not implemented for this spatial backend.')
-
-    # For quoting column values, rather than columns.
-    def geo_quote_name(self, name):
-        return "'%s'" % name
-
-    # GeometryField operations
-    def geo_db_type(self, f):
-        """
-        Returns the database column type for the geometry field on
-        the spatial backend.
-        """
-        raise NotImplementedError('subclasses of BaseSpatialOperations must provide a geo_db_type() method')
-
-    def get_distance(self, f, value, lookup_type):
-        """
-        Returns the distance parameters for the given geometry field,
-        lookup value, and lookup type.
-        """
-        raise NotImplementedError('Distance operations not available on this spatial backend.')
-
-    def get_geom_placeholder(self, f, value, compiler):
-        """
-        Returns the placeholder for the given geometry field with the given
-        value.  Depending on the spatial backend, the placeholder may contain a
-        stored procedure call to the transformation function of the spatial
-        backend.
-        """
-        raise NotImplementedError('subclasses of BaseSpatialOperations must provide a geo_db_placeholder() method')
-
-    # Spatial SQL Construction
-    def spatial_aggregate_sql(self, agg):
-        raise NotImplementedError('Aggregate support not implemented for this spatial backend.')
-
-    # Routines for getting the OGC-compliant models.
-    def geometry_columns(self):
-        raise NotImplementedError('subclasses of BaseSpatialOperations must a provide geometry_columns() method')
-
-    def spatial_ref_sys(self):
-        raise NotImplementedError('subclasses of BaseSpatialOperations must a provide spatial_ref_sys() method')
-
-
 @python_2_unicode_compatible
 class SpatialRefSysMixin(object):
     """

django/contrib/gis/db/backends/base/operations.py

@@ -0,0 +1,114 @@
+class BaseSpatialOperations(object):
+    """
+    This module holds the base `BaseSpatialBackend` object, which is
+    instantiated by each spatial database backend with the features
+    it has.
+    """
+    truncate_params = {}
+
+    # Quick booleans for the type of this spatial backend, and
+    # an attribute for the spatial database version tuple (if applicable)
+    postgis = False
+    spatialite = False
+    mysql = False
+    oracle = False
+    spatial_version = None
+
+    # How the geometry column should be selected.
+    select = None
+
+    # Does the spatial database have a geometry or geography type?
+    geography = False
+    geometry = False
+
+    area = False
+    centroid = False
+    difference = False
+    distance = False
+    distance_sphere = False
+    distance_spheroid = False
+    envelope = False
+    force_rhr = False
+    mem_size = False
+    bounding_circle = False
+    num_geom = False
+    num_points = False
+    perimeter = False
+    perimeter3d = False
+    point_on_surface = False
+    polygonize = False
+    reverse = False
+    scale = False
+    snap_to_grid = False
+    sym_difference = False
+    transform = False
+    translate = False
+    union = False
+
+    # Aggregates
+    collect = False
+    extent = False
+    extent3d = False
+    make_line = False
+    unionagg = False
+
+    # Serialization
+    geohash = False
+    geojson = False
+    gml = False
+    kml = False
+    svg = False
+
+    # Constructors
+    from_text = False
+    from_wkb = False
+
+    # Default conversion functions for aggregates; will be overridden if implemented
+    # for the spatial backend.
+    def convert_extent(self, box, srid):
+        raise NotImplementedError('Aggregate extent not implemented for this spatial backend.')
+
+    def convert_extent3d(self, box, srid):
+        raise NotImplementedError('Aggregate 3D extent not implemented for this spatial backend.')
+
+    def convert_geom(self, geom_val, geom_field):
+        raise NotImplementedError('Aggregate method not implemented for this spatial backend.')
+
+    # For quoting column values, rather than columns.
+    def geo_quote_name(self, name):
+        return "'%s'" % name
+
+    # GeometryField operations
+    def geo_db_type(self, f):
+        """
+        Returns the database column type for the geometry field on
+        the spatial backend.
+        """
+        raise NotImplementedError('subclasses of BaseSpatialOperations must provide a geo_db_type() method')
+
+    def get_distance(self, f, value, lookup_type):
+        """
+        Returns the distance parameters for the given geometry field,
+        lookup value, and lookup type.
+        """
+        raise NotImplementedError('Distance operations not available on this spatial backend.')
+
+    def get_geom_placeholder(self, f, value, compiler):
+        """
+        Returns the placeholder for the given geometry field with the given
+        value.  Depending on the spatial backend, the placeholder may contain a
+        stored procedure call to the transformation function of the spatial
+        backend.
+        """
+        raise NotImplementedError('subclasses of BaseSpatialOperations must provide a geo_db_placeholder() method')
+
+    # Spatial SQL Construction
+    def spatial_aggregate_sql(self, agg):
+        raise NotImplementedError('Aggregate support not implemented for this spatial backend.')
+
+    # Routines for getting the OGC-compliant models.
+    def geometry_columns(self):
+        raise NotImplementedError('subclasses of BaseSpatialOperations must a provide geometry_columns() method')
+
+    def spatial_ref_sys(self):
+        raise NotImplementedError('subclasses of BaseSpatialOperations must a provide spatial_ref_sys() method')

django/contrib/gis/db/backends/mysql/base.py

@@ -1,22 +1,10 @@
-from django.db.backends.mysql.base import (
-    DatabaseWrapper as MySQLDatabaseWrapper,
-    DatabaseFeatures as MySQLDatabaseFeatures,
-)
-from django.contrib.gis.db.backends.base import BaseSpatialFeatures
-from django.contrib.gis.db.backends.mysql.creation import MySQLCreation
-from django.contrib.gis.db.backends.mysql.introspection import MySQLIntrospection
-from django.contrib.gis.db.backends.mysql.operations import MySQLOperations
-from django.contrib.gis.db.backends.mysql.schema import MySQLGISSchemaEditor
+from django.db.backends.mysql.base import DatabaseWrapper as MySQLDatabaseWrapper
 
-
-class DatabaseFeatures(BaseSpatialFeatures, MySQLDatabaseFeatures):
-    has_spatialrefsys_table = False
-    supports_add_srs_entry = False
-    supports_distances_lookups = False
-    supports_transform = False
-    supports_real_shape_operations = False
-    supports_null_geometries = False
-    supports_num_points_poly = False
+from .creation import MySQLCreation
+from .features import DatabaseFeatures
+from .introspection import MySQLIntrospection
+from .operations import MySQLOperations
+from .schema import MySQLGISSchemaEditor
 
 
 class DatabaseWrapper(MySQLDatabaseWrapper):

django/contrib/gis/db/backends/mysql/features.py

@@ -0,0 +1,12 @@
+from django.contrib.gis.db.backends.base.features import BaseSpatialFeatures
+from django.db.backends.mysql.features import DatabaseFeatures as MySQLDatabaseFeatures
+
+
+class DatabaseFeatures(BaseSpatialFeatures, MySQLDatabaseFeatures):
+    has_spatialrefsys_table = False
+    supports_add_srs_entry = False
+    supports_distances_lookups = False
+    supports_transform = False
+    supports_real_shape_operations = False
+    supports_null_geometries = False
+    supports_num_points_poly = False

django/contrib/gis/db/backends/mysql/operations.py

@@ -1,8 +1,7 @@
-from django.db.backends.mysql.base import DatabaseOperations
-
-from django.contrib.gis.db.backends.adapter import WKTAdapter
-from django.contrib.gis.db.backends.base import BaseSpatialOperations
+from django.contrib.gis.db.backends.base.adapter import WKTAdapter
+from django.contrib.gis.db.backends.base.operations import BaseSpatialOperations
 from django.contrib.gis.db.backends.utils import SpatialOperator
+from django.db.backends.mysql.operations import DatabaseOperations
 
 
 class MySQLOperations(DatabaseOperations, BaseSpatialOperations):

django/contrib/gis/db/backends/oracle/adapter.py

@@ -1,5 +1,5 @@
 from cx_Oracle import CLOB
-from django.contrib.gis.db.backends.adapter import WKTAdapter
+from django.contrib.gis.db.backends.base.adapter import WKTAdapter
 
 
 class OracleSpatialAdapter(WKTAdapter):

django/contrib/gis/db/backends/oracle/base.py

@@ -1,17 +1,10 @@
-from django.db.backends.oracle.base import (
-    DatabaseWrapper as OracleDatabaseWrapper,
-    DatabaseFeatures as OracleDatabaseFeatures,
-)
-from django.contrib.gis.db.backends.base import BaseSpatialFeatures
-from django.contrib.gis.db.backends.oracle.creation import OracleCreation
-from django.contrib.gis.db.backends.oracle.introspection import OracleIntrospection
-from django.contrib.gis.db.backends.oracle.operations import OracleOperations
-from django.contrib.gis.db.backends.oracle.schema import OracleGISSchemaEditor
+from django.db.backends.oracle.base import DatabaseWrapper as OracleDatabaseWrapper
 
-
-class DatabaseFeatures(BaseSpatialFeatures, OracleDatabaseFeatures):
-    supports_add_srs_entry = False
-    supports_geometry_field_introspection = False
+from .creation import OracleCreation
+from .features import DatabaseFeatures
+from .introspection import OracleIntrospection
+from .operations import OracleOperations
+from .schema import OracleGISSchemaEditor
 
 
 class DatabaseWrapper(OracleDatabaseWrapper):

django/contrib/gis/db/backends/oracle/features.py

@@ -0,0 +1,7 @@
+from django.contrib.gis.db.backends.base.features import BaseSpatialFeatures
+from django.db.backends.oracle.features import DatabaseFeatures as OracleDatabaseFeatures
+
+
+class DatabaseFeatures(BaseSpatialFeatures, OracleDatabaseFeatures):
+    supports_add_srs_entry = False
+    supports_geometry_field_introspection = False

django/contrib/gis/db/backends/oracle/models.py

@@ -8,7 +8,7 @@
  model and the `SDO_COORD_REF_SYS` is used for the SpatialRefSys model.
 """
 from django.contrib.gis.db import models
-from django.contrib.gis.db.backends.base import SpatialRefSysMixin
+from django.contrib.gis.db.backends.base.models import SpatialRefSysMixin
 from django.utils.encoding import python_2_unicode_compatible
 
 

django/contrib/gis/db/backends/oracle/operations.py

@@ -9,12 +9,13 @@
 """
 import re
 
-from django.db.backends.oracle.base import DatabaseOperations, Database
-from django.contrib.gis.db.backends.base import BaseSpatialOperations
+from django.contrib.gis.db.backends.base.operations import BaseSpatialOperations
 from django.contrib.gis.db.backends.oracle.adapter import OracleSpatialAdapter
 from django.contrib.gis.db.backends.utils import SpatialOperator
 from django.contrib.gis.geometry.backend import Geometry
 from django.contrib.gis.measure import Distance
+from django.db.backends.oracle.base import Database
+from django.db.backends.oracle.operations import DatabaseOperations
 from django.utils import six
 
 

django/contrib/gis/db/backends/postgis/base.py

@@ -1,20 +1,15 @@
 from django.conf import settings
-from django.db.backends import NO_DB_ALIAS
+from django.db.backends.base.base import NO_DB_ALIAS
 from django.db.backends.postgresql_psycopg2.base import (
     DatabaseWrapper as Psycopg2DatabaseWrapper,
-    DatabaseFeatures as Psycopg2DatabaseFeatures
 )
-from django.contrib.gis.db.backends.base import BaseSpatialFeatures
-from django.contrib.gis.db.backends.postgis.creation import PostGISCreation
-from django.contrib.gis.db.backends.postgis.introspection import PostGISIntrospection
-from django.contrib.gis.db.backends.postgis.operations import PostGISOperations
-from django.contrib.gis.db.backends.postgis.schema import PostGISSchemaEditor
 from django.utils.functional import cached_property
 
-
-class DatabaseFeatures(BaseSpatialFeatures, Psycopg2DatabaseFeatures):
-    supports_3d_functions = True
-    supports_left_right_lookups = True
+from .creation import PostGISCreation
+from .features import DatabaseFeatures
+from .introspection import PostGISIntrospection
+from .operations import PostGISOperations
+from .schema import PostGISSchemaEditor
 
 
 class DatabaseWrapper(Psycopg2DatabaseWrapper):

django/contrib/gis/db/backends/postgis/features.py

@@ -0,0 +1,9 @@
+from django.contrib.gis.db.backends.base.features import BaseSpatialFeatures
+from django.db.backends.postgresql_psycopg2.features import (
+    DatabaseFeatures as Psycopg2DatabaseFeatures,
+)
+
+
+class DatabaseFeatures(BaseSpatialFeatures, Psycopg2DatabaseFeatures):
+    supports_3d_functions = True
+    supports_left_right_lookups = True

django/contrib/gis/db/backends/postgis/models.py

@@ -2,7 +2,7 @@
  The GeometryColumns and SpatialRefSys models for the PostGIS backend.
 """
 from django.db import models
-from django.contrib.gis.db.backends.base import SpatialRefSysMixin
+from django.contrib.gis.db.backends.base.models import SpatialRefSysMixin
 from django.utils.encoding import python_2_unicode_compatible
 
 

django/contrib/gis/db/backends/postgis/operations.py

@@ -1,13 +1,13 @@
 import re
 
 from django.conf import settings
-from django.contrib.gis.db.backends.base import BaseSpatialOperations
+from django.contrib.gis.db.backends.base.operations import BaseSpatialOperations
 from django.contrib.gis.db.backends.postgis.adapter import PostGISAdapter
 from django.contrib.gis.db.backends.utils import SpatialOperator
 from django.contrib.gis.geometry.backend import Geometry
 from django.contrib.gis.measure import Distance
 from django.core.exceptions import ImproperlyConfigured
-from django.db.backends.postgresql_psycopg2.base import DatabaseOperations
+from django.db.backends.postgresql_psycopg2.operations import DatabaseOperations
 from django.db.utils import ProgrammingError
 from django.utils.functional import cached_property
 

django/contrib/gis/db/backends/spatialite/adapter.py

@@ -1,5 +1,5 @@
 from django.db.backends.sqlite3.base import Database
-from django.contrib.gis.db.backends.adapter import WKTAdapter
+from django.contrib.gis.db.backends.base.adapter import WKTAdapter
 
 
 class SpatiaLiteAdapter(WKTAdapter):

django/contrib/gis/db/backends/spatialite/base.py

@@ -1,32 +1,19 @@
 import sys
 from ctypes.util import find_library
-from django.conf import settings
 
+from django.conf import settings
 from django.core.exceptions import ImproperlyConfigured
-from django.db.backends.sqlite3.base import (Database,
-    DatabaseWrapper as SQLiteDatabaseWrapper,
-    DatabaseFeatures as SQLiteDatabaseFeatures, SQLiteCursorWrapper)
-from django.contrib.gis.db.backends.base import BaseSpatialFeatures
-from django.contrib.gis.db.backends.spatialite.client import SpatiaLiteClient
-from django.contrib.gis.db.backends.spatialite.creation import SpatiaLiteCreation
-from django.contrib.gis.db.backends.spatialite.introspection import SpatiaLiteIntrospection
-from django.contrib.gis.db.backends.spatialite.operations import SpatiaLiteOperations
-from django.contrib.gis.db.backends.spatialite.schema import SpatialiteSchemaEditor
+from django.db.backends.sqlite3.base import (
+    Database, DatabaseWrapper as SQLiteDatabaseWrapper, SQLiteCursorWrapper,
+)
 from django.utils import six
-from django.utils.functional import cached_property
-
-
-class DatabaseFeatures(BaseSpatialFeatures, SQLiteDatabaseFeatures):
-    supports_distance_geodetic = False
-    # SpatiaLite can only count vertices in LineStrings
-    supports_num_points_poly = False
 
-    @cached_property
-    def supports_initspatialmetadata_in_one_transaction(self):
-        # SpatiaLite 4.1+ support initializing all metadata in one transaction
-        # which can result in a significant performance improvement when
-        # creating the database.
-        return self.connection.ops.spatial_version >= (4, 1, 0)
+from .client import SpatiaLiteClient
+from .creation import SpatiaLiteCreation
+from .features import DatabaseFeatures
+from .introspection import SpatiaLiteIntrospection
+from .operations import SpatiaLiteOperations
+from .schema import SpatialiteSchemaEditor
 
 
 class DatabaseWrapper(SQLiteDatabaseWrapper):

django/contrib/gis/db/backends/spatialite/features.py

@@ -0,0 +1,16 @@
+from django.contrib.gis.db.backends.base.features import BaseSpatialFeatures
+from django.db.backends.sqlite3.features import DatabaseFeatures as SQLiteDatabaseFeatures
+from django.utils.functional import cached_property
+
+
+class DatabaseFeatures(BaseSpatialFeatures, SQLiteDatabaseFeatures):
+    supports_distance_geodetic = False
+    # SpatiaLite can only count vertices in LineStrings
+    supports_num_points_poly = False
+
+    @cached_property
+    def supports_initspatialmetadata_in_one_transaction(self):
+        # SpatiaLite 4.1+ support initializing all metadata in one transaction
+        # which can result in a significant performance improvement when
+        # creating the database.
+        return self.connection.ops.spatial_version >= (4, 1, 0)

django/contrib/gis/db/backends/spatialite/models.py

@@ -3,7 +3,7 @@
 """
 from django.db import connection, models
 from django.db.backends.signals import connection_created
-from django.contrib.gis.db.backends.base import SpatialRefSysMixin
+from django.contrib.gis.db.backends.base.models import SpatialRefSysMixin
 from django.contrib.gis.db.backends.spatialite.base import DatabaseWrapper
 from django.utils.encoding import python_2_unicode_compatible
 

django/contrib/gis/db/backends/spatialite/operations.py

@@ -1,13 +1,13 @@
 import re
 import sys
 
-from django.contrib.gis.db.backends.base import BaseSpatialOperations
+from django.contrib.gis.db.backends.base.operations import BaseSpatialOperations
 from django.contrib.gis.db.backends.utils import SpatialOperator
 from django.contrib.gis.db.backends.spatialite.adapter import SpatiaLiteAdapter
 from django.contrib.gis.geometry.backend import Geometry
 from django.contrib.gis.measure import Distance
 from django.core.exceptions import ImproperlyConfigured
-from django.db.backends.sqlite3.base import DatabaseOperations
+from django.db.backends.sqlite3.operations import DatabaseOperations
 from django.db.utils import DatabaseError
 from django.utils import six
 from django.utils.functional import cached_property

django/db/backends/__init__.py

@@ -1,1540 +0,0 @@
-from collections import deque
-import datetime
-import decimal
-import time
-import warnings
-
-try:
-    from django.utils.six.moves import _thread as thread
-except ImportError:
-    from django.utils.six.moves import _dummy_thread as thread
-from collections import namedtuple
-from contextlib import contextmanager
-from importlib import import_module
-
-from django.conf import settings
-from django.core import checks
-from django.db import DEFAULT_DB_ALIAS
-from django.db.backends.signals import connection_created
-from django.db.backends import utils
-from django.db.transaction import TransactionManagementError
-from django.db.utils import DatabaseError, DatabaseErrorWrapper, ProgrammingError
-from django.utils.dateparse import parse_duration
-from django.utils.deprecation import RemovedInDjango19Warning
-from django.utils.functional import cached_property
-from django.utils import six
-from django.utils import timezone
-
-# Structure returned by DatabaseIntrospection.get_table_list()
-TableInfo = namedtuple('TableInfo', ['name', 'type'])
-
-# Structure returned by the DB-API cursor.description interface (PEP 249)
-FieldInfo = namedtuple('FieldInfo',
-    'name type_code display_size internal_size precision scale null_ok')
-
-NO_DB_ALIAS = '__no_db__'
-
-
-class BaseDatabaseWrapper(object):
-    """
-    Represents a database connection.
-    """
-    # Mapping of Field objects to their column types.
-    data_types = {}
-    # Mapping of Field objects to their SQL suffix such as AUTOINCREMENT.
-    data_types_suffix = {}
-    # Mapping of Field objects to their SQL for CHECK constraints.
-    data_type_check_constraints = {}
-    ops = None
-    vendor = 'unknown'
-    SchemaEditorClass = None
-
-    queries_limit = 9000
-
-    def __init__(self, settings_dict, alias=DEFAULT_DB_ALIAS,
-                 allow_thread_sharing=False):
-        # Connection related attributes.
-        # The underlying database connection.
-        self.connection = None
-        # `settings_dict` should be a dictionary containing keys such as
-        # NAME, USER, etc. It's called `settings_dict` instead of `settings`
-        # to disambiguate it from Django settings modules.
-        self.settings_dict = settings_dict
-        self.alias = alias
-        # Query logging in debug mode or when explicitly enabled.
-        self.queries_log = deque(maxlen=self.queries_limit)
-        self.force_debug_cursor = False
-
-        # Transaction related attributes.
-        # Tracks if the connection is in autocommit mode. Per PEP 249, by
-        # default, it isn't.
-        self.autocommit = False
-        # Tracks if the connection is in a transaction managed by 'atomic'.
-        self.in_atomic_block = False
-        # Increment to generate unique savepoint ids.
-        self.savepoint_state = 0
-        # List of savepoints created by 'atomic'.
-        self.savepoint_ids = []
-        # Tracks if the outermost 'atomic' block should commit on exit,
-        # ie. if autocommit was active on entry.
-        self.commit_on_exit = True
-        # Tracks if the transaction should be rolled back to the next
-        # available savepoint because of an exception in an inner block.
-        self.needs_rollback = False
-
-        # Connection termination related attributes.
-        self.close_at = None
-        self.closed_in_transaction = False
-        self.errors_occurred = False
-
-        # Thread-safety related attributes.
-        self.allow_thread_sharing = allow_thread_sharing
-        self._thread_ident = thread.get_ident()
-
-    @property
-    def queries_logged(self):
-        return self.force_debug_cursor or settings.DEBUG
-
-    @property
-    def queries(self):
-        if len(self.queries_log) == self.queries_log.maxlen:
-            warnings.warn(
-                "Limit for query logging exceeded, only the last {} queries "
-                "will be returned.".format(self.queries_log.maxlen))
-        return list(self.queries_log)
-
-    ##### Backend-specific methods for creating connections and cursors #####
-
-    def get_connection_params(self):
-        """Returns a dict of parameters suitable for get_new_connection."""
-        raise NotImplementedError('subclasses of BaseDatabaseWrapper may require a get_connection_params() method')
-
-    def get_new_connection(self, conn_params):
-        """Opens a connection to the database."""
-        raise NotImplementedError('subclasses of BaseDatabaseWrapper may require a get_new_connection() method')
-
-    def init_connection_state(self):
-        """Initializes the database connection settings."""
-        raise NotImplementedError('subclasses of BaseDatabaseWrapper may require an init_connection_state() method')
-
-    def create_cursor(self):
-        """Creates a cursor. Assumes that a connection is established."""
-        raise NotImplementedError('subclasses of BaseDatabaseWrapper may require a create_cursor() method')
-
-    ##### Backend-specific methods for creating connections #####
-
-    def connect(self):
-        """Connects to the database. Assumes that the connection is closed."""
-        # In case the previous connection was closed while in an atomic block
-        self.in_atomic_block = False
-        self.savepoint_ids = []
-        self.needs_rollback = False
-        # Reset parameters defining when to close the connection
-        max_age = self.settings_dict['CONN_MAX_AGE']
-        self.close_at = None if max_age is None else time.time() + max_age
-        self.closed_in_transaction = False
-        self.errors_occurred = False
-        # Establish the connection
-        conn_params = self.get_connection_params()
-        self.connection = self.get_new_connection(conn_params)
-        self.set_autocommit(self.settings_dict['AUTOCOMMIT'])
-        self.init_connection_state()
-        connection_created.send(sender=self.__class__, connection=self)
-
-    def ensure_connection(self):
-        """
-        Guarantees that a connection to the database is established.
-        """
-        if self.connection is None:
-            with self.wrap_database_errors:
-                self.connect()
-
-    ##### Backend-specific wrappers for PEP-249 connection methods #####
-
-    def _cursor(self):
-        self.ensure_connection()
-        with self.wrap_database_errors:
-            return self.create_cursor()
-
-    def _commit(self):
-        if self.connection is not None:
-            with self.wrap_database_errors:
-                return self.connection.commit()
-
-    def _rollback(self):
-        if self.connection is not None:
-            with self.wrap_database_errors:
-                return self.connection.rollback()
-
-    def _close(self):
-        if self.connection is not None:
-            with self.wrap_database_errors:
-                return self.connection.close()
-
-    ##### Generic wrappers for PEP-249 connection methods #####
-
-    def cursor(self):
-        """
-        Creates a cursor, opening a connection if necessary.
-        """
-        self.validate_thread_sharing()
-        if self.queries_logged:
-            cursor = self.make_debug_cursor(self._cursor())
-        else:
-            cursor = self.make_cursor(self._cursor())
-        return cursor
-
-    def commit(self):
-        """
-        Commits a transaction and resets the dirty flag.
-        """
-        self.validate_thread_sharing()
-        self.validate_no_atomic_block()
-        self._commit()
-        # A successful commit means that the database connection works.
-        self.errors_occurred = False
-
-    def rollback(self):
-        """
-        Rolls back a transaction and resets the dirty flag.
-        """
-        self.validate_thread_sharing()
-        self.validate_no_atomic_block()
-        self._rollback()
-        # A successful rollback means that the database connection works.
-        self.errors_occurred = False
-
-    def close(self):
-        """
-        Closes the connection to the database.
-        """
-        self.validate_thread_sharing()
-        # Don't call validate_no_atomic_block() to avoid making it difficult
-        # to get rid of a connection in an invalid state. The next connect()
-        # will reset the transaction state anyway.
-        if self.closed_in_transaction or self.connection is None:
-            return
-        try:
-            self._close()
-        finally:
-            if self.in_atomic_block:
-                self.closed_in_transaction = True
-                self.needs_rollback = True
-            else:
-                self.connection = None
-
-    ##### Backend-specific savepoint management methods #####
-
-    def _savepoint(self, sid):
-        with self.cursor() as cursor:
-            cursor.execute(self.ops.savepoint_create_sql(sid))
-
-    def _savepoint_rollback(self, sid):
-        with self.cursor() as cursor:
-            cursor.execute(self.ops.savepoint_rollback_sql(sid))
-
-    def _savepoint_commit(self, sid):
-        with self.cursor() as cursor:
-            cursor.execute(self.ops.savepoint_commit_sql(sid))
-
-    def _savepoint_allowed(self):
-        # Savepoints cannot be created outside a transaction
-        return self.features.uses_savepoints and not self.get_autocommit()
-
-    ##### Generic savepoint management methods #####
-
-    def savepoint(self):
-        """
-        Creates a savepoint inside the current transaction. Returns an
-        identifier for the savepoint that will be used for the subsequent
-        rollback or commit. Does nothing if savepoints are not supported.
-        """
-        if not self._savepoint_allowed():
-            return
-
-        thread_ident = thread.get_ident()
-        tid = str(thread_ident).replace('-', '')
-
-        self.savepoint_state += 1
-        sid = "s%s_x%d" % (tid, self.savepoint_state)
-
-        self.validate_thread_sharing()
-        self._savepoint(sid)
-
-        return sid
-
-    def savepoint_rollback(self, sid):
-        """
-        Rolls back to a savepoint. Does nothing if savepoints are not supported.
-        """
-        if not self._savepoint_allowed():
-            return
-
-        self.validate_thread_sharing()
-        self._savepoint_rollback(sid)
-
-    def savepoint_commit(self, sid):
-        """
-        Releases a savepoint. Does nothing if savepoints are not supported.
-        """
-        if not self._savepoint_allowed():
-            return
-
-        self.validate_thread_sharing()
-        self._savepoint_commit(sid)
-
-    def clean_savepoints(self):
-        """
-        Resets the counter used to generate unique savepoint ids in this thread.
-        """
-        self.savepoint_state = 0
-
-    ##### Backend-specific transaction management methods #####
-
-    def _set_autocommit(self, autocommit):
-        """
-        Backend-specific implementation to enable or disable autocommit.
-        """
-        raise NotImplementedError('subclasses of BaseDatabaseWrapper may require a _set_autocommit() method')
-
-    ##### Generic transaction management methods #####
-
-    def get_autocommit(self):
-        """
-        Check the autocommit state.
-        """
-        self.ensure_connection()
-        return self.autocommit
-
-    def set_autocommit(self, autocommit):
-        """
-        Enable or disable autocommit.
-        """
-        self.validate_no_atomic_block()
-        self.ensure_connection()
-        self._set_autocommit(autocommit)
-        self.autocommit = autocommit
-
-    def get_rollback(self):
-        """
-        Get the "needs rollback" flag -- for *advanced use* only.
-        """
-        if not self.in_atomic_block:
-            raise TransactionManagementError(
-                "The rollback flag doesn't work outside of an 'atomic' block.")
-        return self.needs_rollback
-
-    def set_rollback(self, rollback):
-        """
-        Set or unset the "needs rollback" flag -- for *advanced use* only.
-        """
-        if not self.in_atomic_block:
-            raise TransactionManagementError(
-                "The rollback flag doesn't work outside of an 'atomic' block.")
-        self.needs_rollback = rollback
-
-    def validate_no_atomic_block(self):
-        """
-        Raise an error if an atomic block is active.
-        """
-        if self.in_atomic_block:
-            raise TransactionManagementError(
-                "This is forbidden when an 'atomic' block is active.")
-
-    def validate_no_broken_transaction(self):
-        if self.needs_rollback:
-            raise TransactionManagementError(
-                "An error occurred in the current transaction. You can't "
-                "execute queries until the end of the 'atomic' block.")
-
-    ##### Foreign key constraints checks handling #####
-
-    @contextmanager
-    def constraint_checks_disabled(self):
-        """
-        Context manager that disables foreign key constraint checking.
-        """
-        disabled = self.disable_constraint_checking()
-        try:
-            yield
-        finally:
-            if disabled:
-                self.enable_constraint_checking()
-
-    def disable_constraint_checking(self):
-        """
-        Backends can implement as needed to temporarily disable foreign key
-        constraint checking. Should return True if the constraints were
-        disabled and will need to be reenabled.
-        """
-        return False
-
-    def enable_constraint_checking(self):
-        """
-        Backends can implement as needed to re-enable foreign key constraint
-        checking.
-        """
-        pass
-
-    def check_constraints(self, table_names=None):
-        """
-        Backends can override this method if they can apply constraint
-        checking (e.g. via "SET CONSTRAINTS ALL IMMEDIATE"). Should raise an
-        IntegrityError if any invalid foreign key references are encountered.
-        """
-        pass
-
-    ##### Connection termination handling #####
-
-    def is_usable(self):
-        """
-        Tests if the database connection is usable.
-
-        This function may assume that self.connection is not None.
-
-        Actual implementations should take care not to raise exceptions
-        as that may prevent Django from recycling unusable connections.
-        """
-        raise NotImplementedError(
-            "subclasses of BaseDatabaseWrapper may require an is_usable() method")
-
-    def close_if_unusable_or_obsolete(self):
-        """
-        Closes the current connection if unrecoverable errors have occurred,
-        or if it outlived its maximum age.
-        """
-        if self.connection is not None:
-            # If the application didn't restore the original autocommit setting,
-            # don't take chances, drop the connection.
-            if self.get_autocommit() != self.settings_dict['AUTOCOMMIT']:
-                self.close()
-                return
-
-            # If an exception other than DataError or IntegrityError occurred
-            # since the last commit / rollback, check if the connection works.
-            if self.errors_occurred:
-                if self.is_usable():
-                    self.errors_occurred = False
-                else:
-                    self.close()
-                    return
-
-            if self.close_at is not None and time.time() >= self.close_at:
-                self.close()
-                return
-
-    ##### Thread safety handling #####
-
-    def validate_thread_sharing(self):
-        """
-        Validates that the connection isn't accessed by another thread than the
-        one which originally created it, unless the connection was explicitly
-        authorized to be shared between threads (via the `allow_thread_sharing`
-        property). Raises an exception if the validation fails.
-        """
-        if not (self.allow_thread_sharing
-                or self._thread_ident == thread.get_ident()):
-            raise DatabaseError("DatabaseWrapper objects created in a "
-                "thread can only be used in that same thread. The object "
-                "with alias '%s' was created in thread id %s and this is "
-                "thread id %s."
-                % (self.alias, self._thread_ident, thread.get_ident()))
-
-    ##### Miscellaneous #####
-
-    def prepare_database(self):
-        """
-        Hook to do any database check or preparation, generally called before
-        migrating a project or an app.
-        """
-        pass
-
-    @cached_property
-    def wrap_database_errors(self):
-        """
-        Context manager and decorator that re-throws backend-specific database
-        exceptions using Django's common wrappers.
-        """
-        return DatabaseErrorWrapper(self)
-
-    def make_debug_cursor(self, cursor):
-        """
-        Creates a cursor that logs all queries in self.queries_log.
-        """
-        return utils.CursorDebugWrapper(cursor, self)
-
-    def make_cursor(self, cursor):
-        """
-        Creates a cursor without debug logging.
-        """
-        return utils.CursorWrapper(cursor, self)
-
-    @contextmanager
-    def temporary_connection(self):
-        """
-        Context manager that ensures that a connection is established, and
-        if it opened one, closes it to avoid leaving a dangling connection.
-        This is useful for operations outside of the request-response cycle.
-
-        Provides a cursor: with self.temporary_connection() as cursor: ...
-        """
-        must_close = self.connection is None
-        cursor = self.cursor()
-        try:
-            yield cursor
-        finally:
-            cursor.close()
-            if must_close:
-                self.close()
-
-    @cached_property
-    def _nodb_connection(self):
-        """
-        Alternative connection to be used when there is no need to access
-        the main database, specifically for test db creation/deletion.
-        This also prevents the production database from being exposed to
-        potential child threads while (or after) the test database is destroyed.
-        Refs #10868, #17786, #16969.
-        """
-        settings_dict = self.settings_dict.copy()
-        settings_dict['NAME'] = None
-        #backend = load_backend(settings_dict['ENGINE'])
-        nodb_connection = self.__class__(
-            settings_dict,
-            alias=NO_DB_ALIAS,
-            allow_thread_sharing=False)
-        return nodb_connection
-
-    def _start_transaction_under_autocommit(self):
-        """
-        Only required when autocommits_when_autocommit_is_off = True.
-        """
-        raise NotImplementedError(
-            'subclasses of BaseDatabaseWrapper may require a '
-            '_start_transaction_under_autocommit() method'
-        )
-
-    def schema_editor(self, *args, **kwargs):
-        """
-        Returns a new instance of this backend's SchemaEditor.
-        """
-        if self.SchemaEditorClass is None:
-            raise NotImplementedError(
-                'The SchemaEditorClass attribute of this database wrapper is still None')
-        return self.SchemaEditorClass(self, *args, **kwargs)
-
-
-class BaseDatabaseFeatures(object):
-    gis_enabled = False
-    allows_group_by_pk = False
-    # True if django.db.backends.utils.typecast_timestamp is used on values
-    # returned from dates() calls.
-    needs_datetime_string_cast = True
-    empty_fetchmany_value = []
-    update_can_self_select = True
-
-    # Does the backend distinguish between '' and None?
-    interprets_empty_strings_as_nulls = False
-
-    # Does the backend allow inserting duplicate NULL rows in a nullable
-    # unique field? All core backends implement this correctly, but other
-    # databases such as SQL Server do not.
-    supports_nullable_unique_constraints = True
-
-    # Does the backend allow inserting duplicate rows when a unique_together
-    # constraint exists and some fields are nullable but not all of them?
-    supports_partially_nullable_unique_constraints = True
-
-    can_use_chunked_reads = True
-    can_return_id_from_insert = False
-    has_bulk_insert = False
-    uses_savepoints = False
-    can_release_savepoints = False
-    can_combine_inserts_with_and_without_auto_increment_pk = False
-
-    # If True, don't use integer foreign keys referring to, e.g., positive
-    # integer primary keys.
-    related_fields_match_type = False
-    allow_sliced_subqueries = True
-    has_select_for_update = False
-    has_select_for_update_nowait = False
-
-    supports_select_related = True
-
-    # Does the default test database allow multiple connections?
-    # Usually an indication that the test database is in-memory
-    test_db_allows_multiple_connections = True
-
-    # Can an object be saved without an explicit primary key?
-    supports_unspecified_pk = False
-
-    # Can a fixture contain forward references? i.e., are
-    # FK constraints checked at the end of transaction, or
-    # at the end of each save operation?
-    supports_forward_references = True
-
-    # Does the backend truncate names properly when they are too long?
-    truncates_names = False
-
-    # Is there a REAL datatype in addition to floats/doubles?
-    has_real_datatype = False
-    supports_subqueries_in_group_by = True
-    supports_bitwise_or = True
-
-    # Is there a true datatype for timedeltas?
-    has_native_duration_field = False
-
-    # Does the database driver support timedeltas as arguments?
-    # This is only relevant when there is a native duration field.
-    # Specifically, there is a bug with cx_Oracle:
-    # https://bitbucket.org/anthony_tuininga/cx_oracle/issue/7/
-    driver_supports_timedelta_args = False
-
-    # Do time/datetime fields have microsecond precision?
-    supports_microsecond_precision = True
-
-    # Does the __regex lookup support backreferencing and grouping?
-    supports_regex_backreferencing = True
-
-    # Can date/datetime lookups be performed using a string?
-    supports_date_lookup_using_string = True
-
-    # Can datetimes with timezones be used?
-    supports_timezones = True
-
-    # Does the database have a copy of the zoneinfo database?
-    has_zoneinfo_database = True
-
-    # When performing a GROUP BY, is an ORDER BY NULL required
-    # to remove any ordering?
-    requires_explicit_null_ordering_when_grouping = False
-
-    # Does the backend order NULL values as largest or smallest?
-    nulls_order_largest = False
-
-    # Is there a 1000 item limit on query parameters?
-    supports_1000_query_parameters = True
-
-    # Can an object have an autoincrement primary key of 0? MySQL says No.
-    allows_auto_pk_0 = True
-
-    # Do we need to NULL a ForeignKey out, or can the constraint check be
-    # deferred
-    can_defer_constraint_checks = False
-
-    # date_interval_sql can properly handle mixed Date/DateTime fields and timedeltas
-    supports_mixed_date_datetime_comparisons = True
-
-    # Does the backend support tablespaces? Default to False because it isn't
-    # in the SQL standard.
-    supports_tablespaces = False
-
-    # Does the backend reset sequences between tests?
-    supports_sequence_reset = True
-
-    # Can the backend determine reliably the length of a CharField?
-    can_introspect_max_length = True
-
-    # Can the backend determine reliably if a field is nullable?
-    # Note that this is separate from interprets_empty_strings_as_nulls,
-    # although the latter feature, when true, interferes with correct
-    # setting (and introspection) of CharFields' nullability.
-    # This is True for all core backends.
-    can_introspect_null = True
-
-    # Confirm support for introspected foreign keys
-    # Every database can do this reliably, except MySQL,
-    # which can't do it for MyISAM tables
-    can_introspect_foreign_keys = True
-
-    # Can the backend introspect an AutoField, instead of an IntegerField?
-    can_introspect_autofield = False
-
-    # Can the backend introspect a BigIntegerField, instead of an IntegerField?
-    can_introspect_big_integer_field = True
-
-    # Can the backend introspect an BinaryField, instead of an TextField?
-    can_introspect_binary_field = True
-
-    # Can the backend introspect an DecimalField, instead of an FloatField?
-    can_introspect_decimal_field = True
-
-    # Can the backend introspect an IPAddressField, instead of an CharField?
-    can_introspect_ip_address_field = False
-
-    # Can the backend introspect a PositiveIntegerField, instead of an IntegerField?
-    can_introspect_positive_integer_field = False
-
-    # Can the backend introspect a SmallIntegerField, instead of an IntegerField?
-    can_introspect_small_integer_field = False
-
-    # Can the backend introspect a TimeField, instead of a DateTimeField?
-    can_introspect_time_field = True
-
-    # Support for the DISTINCT ON clause
-    can_distinct_on_fields = False
-
-    # Does the backend decide to commit before SAVEPOINT statements
-    # when autocommit is disabled? http://bugs.python.org/issue8145#msg109965
-    autocommits_when_autocommit_is_off = False
-
-    # Does the backend prevent running SQL queries in broken transactions?
-    atomic_transactions = True
-
-    # Can we roll back DDL in a transaction?
-    can_rollback_ddl = False
-
-    # Can we issue more than one ALTER COLUMN clause in an ALTER TABLE?
-    supports_combined_alters = False
-
-    # Does it support foreign keys?
-    supports_foreign_keys = True
-
-    # Does it support CHECK constraints?
-    supports_column_check_constraints = True
-
-    # Does the backend support 'pyformat' style ("... %(name)s ...", {'name': value})
-    # parameter passing? Note this can be provided by the backend even if not
-    # supported by the Python driver
-    supports_paramstyle_pyformat = True
-
-    # Does the backend require literal defaults, rather than parameterized ones?
-    requires_literal_defaults = False
-
-    # Does the backend require a connection reset after each material schema change?
-    connection_persists_old_columns = False
-
-    # What kind of error does the backend throw when accessing closed cursor?
-    closed_cursor_error_class = ProgrammingError
-
-    # Does 'a' LIKE 'A' match?
-    has_case_insensitive_like = True
-
-    # Does the backend require the sqlparse library for splitting multi-line
-    # statements before executing them?
-    requires_sqlparse_for_splitting = True
-
-    # Suffix for backends that don't support "SELECT xxx;" queries.
-    bare_select_suffix = ''
-
-    # If NULL is implied on columns without needing to be explicitly specified
-    implied_column_null = False
-
-    uppercases_column_names = False
-
-    # Does the backend support "select for update" queries with limit (and offset)?
-    supports_select_for_update_with_limit = True
-
-    def __init__(self, connection):
-        self.connection = connection
-
-    @cached_property
-    def supports_transactions(self):
-        """Confirm support for transactions."""
-        with self.connection.cursor() as cursor:
-            cursor.execute('CREATE TABLE ROLLBACK_TEST (X INT)')
-            self.connection.set_autocommit(False)
-            cursor.execute('INSERT INTO ROLLBACK_TEST (X) VALUES (8)')
-            self.connection.rollback()
-            self.connection.set_autocommit(True)
-            cursor.execute('SELECT COUNT(X) FROM ROLLBACK_TEST')
-            count, = cursor.fetchone()
-            cursor.execute('DROP TABLE ROLLBACK_TEST')
-        return count == 0
-
-    @cached_property
-    def supports_stddev(self):
-        """Confirm support for STDDEV and related stats functions."""
-        class StdDevPop(object):
-            sql_function = 'STDDEV_POP'
-
-        try:
-            self.connection.ops.check_aggregate_support(StdDevPop())
-            return True
-        except NotImplementedError:
-            return False
-
-    def introspected_boolean_field_type(self, field=None, created_separately=False):
-        """
-        What is the type returned when the backend introspects a BooleanField?
-        The optional arguments may be used to give further details of the field to be
-        introspected; in particular, they are provided by Django's test suite:
-        field -- the field definition
-        created_separately -- True if the field was added via a SchemaEditor's AddField,
-                              False if the field was created with the model
-
-        Note that return value from this function is compared by tests against actual
-        introspection results; it should provide expectations, not run an introspection
-        itself.
-        """
-        if self.can_introspect_null and field and field.null:
-            return 'NullBooleanField'
-        return 'BooleanField'
-
-
-class BaseDatabaseOperations(object):
-    """
-    This class encapsulates all backend-specific differences, such as the way
-    a backend performs ordering or calculates the ID of a recently-inserted
-    row.
-    """
-    compiler_module = "django.db.models.sql.compiler"
-
-    # Integer field safe ranges by `internal_type` as documented
-    # in docs/ref/models/fields.txt.
-    integer_field_ranges = {
-        'SmallIntegerField': (-32768, 32767),
-        'IntegerField': (-2147483648, 2147483647),
-        'BigIntegerField': (-9223372036854775808, 9223372036854775807),
-        'PositiveSmallIntegerField': (0, 32767),
-        'PositiveIntegerField': (0, 2147483647),
-    }
-
-    def __init__(self, connection):
-        self.connection = connection
-        self._cache = None
-
-    def autoinc_sql(self, table, column):
-        """
-        Returns any SQL needed to support auto-incrementing primary keys, or
-        None if no SQL is necessary.
-
-        This SQL is executed when a table is created.
-        """
-        return None
-
-    def bulk_batch_size(self, fields, objs):
-        """
-        Returns the maximum allowed batch size for the backend. The fields
-        are the fields going to be inserted in the batch, the objs contains
-        all the objects to be inserted.
-        """
-        return len(objs)
-
-    def cache_key_culling_sql(self):
-        """
-        Returns an SQL query that retrieves the first cache key greater than the
-        n smallest.
-
-        This is used by the 'db' cache backend to determine where to start
-        culling.
-        """
-        return "SELECT cache_key FROM %s ORDER BY cache_key LIMIT 1 OFFSET %%s"
-
-    def unification_cast_sql(self, output_field):
-        """
-        Given a field instance, returns the SQL necessary to cast the result of
-        a union to that type. Note that the resulting string should contain a
-        '%s' placeholder for the expression being cast.
-        """
-        return '%s'
-
-    def date_extract_sql(self, lookup_type, field_name):
-        """
-        Given a lookup_type of 'year', 'month' or 'day', returns the SQL that
-        extracts a value from the given date field field_name.
-        """
-        raise NotImplementedError('subclasses of BaseDatabaseOperations may require a date_extract_sql() method')
-
-    def date_interval_sql(self, sql, connector, timedelta):
-        """
-        Implements the date interval functionality for expressions
-        """
-        raise NotImplementedError('subclasses of BaseDatabaseOperations may require a date_interval_sql() method')
-
-    def date_trunc_sql(self, lookup_type, field_name):
-        """
-        Given a lookup_type of 'year', 'month' or 'day', returns the SQL that
-        truncates the given date field field_name to a date object with only
-        the given specificity.
-        """
-        raise NotImplementedError('subclasses of BaseDatabaseOperations may require a datetrunc_sql() method')
-
-    def datetime_cast_sql(self):
-        """
-        Returns the SQL necessary to cast a datetime value so that it will be
-        retrieved as a Python datetime object instead of a string.
-
-        This SQL should include a '%s' in place of the field's name.
-        """
-        return "%s"
-
-    def datetime_extract_sql(self, lookup_type, field_name, tzname):
-        """
-        Given a lookup_type of 'year', 'month', 'day', 'hour', 'minute' or
-        'second', returns the SQL that extracts a value from the given
-        datetime field field_name, and a tuple of parameters.
-        """
-        raise NotImplementedError('subclasses of BaseDatabaseOperations may require a datetime_extract_sql() method')
-
-    def datetime_trunc_sql(self, lookup_type, field_name, tzname):
-        """
-        Given a lookup_type of 'year', 'month', 'day', 'hour', 'minute' or
-        'second', returns the SQL that truncates the given datetime field
-        field_name to a datetime object with only the given specificity, and
-        a tuple of parameters.
-        """
-        raise NotImplementedError('subclasses of BaseDatabaseOperations may require a datetime_trunk_sql() method')
-
-    def deferrable_sql(self):
-        """
-        Returns the SQL necessary to make a constraint "initially deferred"
-        during a CREATE TABLE statement.
-        """
-        return ''
-
-    def distinct_sql(self, fields):
-        """
-        Returns an SQL DISTINCT clause which removes duplicate rows from the
-        result set. If any fields are given, only the given fields are being
-        checked for duplicates.
-        """
-        if fields:
-            raise NotImplementedError('DISTINCT ON fields is not supported by this database backend')
-        else:
-            return 'DISTINCT'
-
-    def drop_foreignkey_sql(self):
-        """
-        Returns the SQL command that drops a foreign key.
-        """
-        return "DROP CONSTRAINT"
-
-    def drop_sequence_sql(self, table):
-        """
-        Returns any SQL necessary to drop the sequence for the given table.
-        Returns None if no SQL is necessary.
-        """
-        return None
-
-    def fetch_returned_insert_id(self, cursor):
-        """
-        Given a cursor object that has just performed an INSERT...RETURNING
-        statement into a table that has an auto-incrementing ID, returns the
-        newly created ID.
-        """
-        return cursor.fetchone()[0]
-
-    def field_cast_sql(self, db_type, internal_type):
-        """
-        Given a column type (e.g. 'BLOB', 'VARCHAR'), and an internal type
-        (e.g. 'GenericIPAddressField'), returns the SQL necessary to cast it
-        before using it in a WHERE statement. Note that the resulting string
-        should contain a '%s' placeholder for the column being searched against.
-        """
-        return '%s'
-
-    def force_no_ordering(self):
-        """
-        Returns a list used in the "ORDER BY" clause to force no ordering at
-        all. Returning an empty list means that nothing will be included in the
-        ordering.
-        """
-        return []
-
-    def for_update_sql(self, nowait=False):
-        """
-        Returns the FOR UPDATE SQL clause to lock rows for an update operation.
-        """
-        if nowait:
-            return 'FOR UPDATE NOWAIT'
-        else:
-            return 'FOR UPDATE'
-
-    def fulltext_search_sql(self, field_name):
-        """
-        Returns the SQL WHERE clause to use in order to perform a full-text
-        search of the given field_name. Note that the resulting string should
-        contain a '%s' placeholder for the value being searched against.
-        """
-        raise NotImplementedError('Full-text search is not implemented for this database backend')
-
-    def last_executed_query(self, cursor, sql, params):
-        """
-        Returns a string of the query last executed by the given cursor, with
-        placeholders replaced with actual values.
-
-        `sql` is the raw query containing placeholders, and `params` is the
-        sequence of parameters. These are used by default, but this method
-        exists for database backends to provide a better implementation
-        according to their own quoting schemes.
-        """
-        from django.utils.encoding import force_text
-
-        # Convert params to contain Unicode values.
-        to_unicode = lambda s: force_text(s, strings_only=True, errors='replace')
-        if isinstance(params, (list, tuple)):
-            u_params = tuple(to_unicode(val) for val in params)
-        elif params is None:
-            u_params = ()
-        else:
-            u_params = {to_unicode(k): to_unicode(v) for k, v in params.items()}
-
-        return six.text_type("QUERY = %r - PARAMS = %r") % (sql, u_params)
-
-    def last_insert_id(self, cursor, table_name, pk_name):
-        """
-        Given a cursor object that has just performed an INSERT statement into
-        a table that has an auto-incrementing ID, returns the newly created ID.
-
-        This method also receives the table name and the name of the primary-key
-        column.
-        """
-        return cursor.lastrowid
-
-    def lookup_cast(self, lookup_type):
-        """
-        Returns the string to use in a query when performing lookups
-        ("contains", "like", etc). The resulting string should contain a '%s'
-        placeholder for the column being searched against.
-        """
-        return "%s"
-
-    def max_in_list_size(self):
-        """
-        Returns the maximum number of items that can be passed in a single 'IN'
-        list condition, or None if the backend does not impose a limit.
-        """
-        return None
-
-    def max_name_length(self):
-        """
-        Returns the maximum length of table and column names, or None if there
-        is no limit.
-        """
-        return None
-
-    def no_limit_value(self):
-        """
-        Returns the value to use for the LIMIT when we are wanting "LIMIT
-        infinity". Returns None if the limit clause can be omitted in this case.
-        """
-        raise NotImplementedError('subclasses of BaseDatabaseOperations may require a no_limit_value() method')
-
-    def pk_default_value(self):
-        """
-        Returns the value to use during an INSERT statement to specify that
-        the field should use its default value.
-        """
-        return 'DEFAULT'
-
-    def prepare_sql_script(self, sql, _allow_fallback=False):
-        """
-        Takes a SQL script that may contain multiple lines and returns a list
-        of statements to feed to successive cursor.execute() calls.
-
-        Since few databases are able to process raw SQL scripts in a single
-        cursor.execute() call and PEP 249 doesn't talk about this use case,
-        the default implementation is conservative.
-        """
-        # Remove _allow_fallback and keep only 'return ...' in Django 1.9.
-        try:
-            # This import must stay inside the method because it's optional.
-            import sqlparse
-        except ImportError:
-            if _allow_fallback:
-                # Without sqlparse, fall back to the legacy (and buggy) logic.
-                warnings.warn(
-                    "Providing initial SQL data on a %s database will require "
-                    "sqlparse in Django 1.9." % self.connection.vendor,
-                    RemovedInDjango19Warning)
-                from django.core.management.sql import _split_statements
-                return _split_statements(sql)
-            else:
-                raise
-        else:
-            return [sqlparse.format(statement, strip_comments=True)
-                    for statement in sqlparse.split(sql) if statement]
-
-    def process_clob(self, value):
-        """
-        Returns the value of a CLOB column, for backends that return a locator
-        object that requires additional processing.
-        """
-        return value
-
-    def return_insert_id(self):
-        """
-        For backends that support returning the last insert ID as part
-        of an insert query, this method returns the SQL and params to
-        append to the INSERT query. The returned fragment should
-        contain a format string to hold the appropriate column.
-        """
-        pass
-
-    def compiler(self, compiler_name):
-        """
-        Returns the SQLCompiler class corresponding to the given name,
-        in the namespace corresponding to the `compiler_module` attribute
-        on this backend.
-        """
-        if self._cache is None:
-            self._cache = import_module(self.compiler_module)
-        return getattr(self._cache, compiler_name)
-
-    def quote_name(self, name):
-        """
-        Returns a quoted version of the given table, index or column name. Does
-        not quote the given name if it's already been quoted.
-        """
-        raise NotImplementedError('subclasses of BaseDatabaseOperations may require a quote_name() method')
-
-    def random_function_sql(self):
-        """
-        Returns an SQL expression that returns a random value.
-        """
-        return 'RANDOM()'
-
-    def regex_lookup(self, lookup_type):
-        """
-        Returns the string to use in a query when performing regular expression
-        lookups (using "regex" or "iregex"). The resulting string should
-        contain a '%s' placeholder for the column being searched against.
-
-        If the feature is not supported (or part of it is not supported), a
-        NotImplementedError exception can be raised.
-        """
-        raise NotImplementedError('subclasses of BaseDatabaseOperations may require a regex_lookup() method')
-
-    def savepoint_create_sql(self, sid):
-        """
-        Returns the SQL for starting a new savepoint. Only required if the
-        "uses_savepoints" feature is True. The "sid" parameter is a string
-        for the savepoint id.
-        """
-        return "SAVEPOINT %s" % self.quote_name(sid)
-
-    def savepoint_commit_sql(self, sid):
-        """
-        Returns the SQL for committing the given savepoint.
-        """
-        return "RELEASE SAVEPOINT %s" % self.quote_name(sid)
-
-    def savepoint_rollback_sql(self, sid):
-        """
-        Returns the SQL for rolling back the given savepoint.
-        """
-        return "ROLLBACK TO SAVEPOINT %s" % self.quote_name(sid)
-
-    def set_time_zone_sql(self):
-        """
-        Returns the SQL that will set the connection's time zone.
-
-        Returns '' if the backend doesn't support time zones.
-        """
-        return ''
-
-    def sql_flush(self, style, tables, sequences, allow_cascade=False):
-        """
-        Returns a list of SQL statements required to remove all data from
-        the given database tables (without actually removing the tables
-        themselves).
-
-        The returned value also includes SQL statements required to reset DB
-        sequences passed in :param sequences:.
-
-        The `style` argument is a Style object as returned by either
-        color_style() or no_style() in django.core.management.color.
-
-        The `allow_cascade` argument determines whether truncation may cascade
-        to tables with foreign keys pointing the tables being truncated.
-        PostgreSQL requires a cascade even if these tables are empty.
-        """
-        raise NotImplementedError('subclasses of BaseDatabaseOperations must provide a sql_flush() method')
-
-    def sequence_reset_by_name_sql(self, style, sequences):
-        """
-        Returns a list of the SQL statements required to reset sequences
-        passed in :param sequences:.
-
-        The `style` argument is a Style object as returned by either
-        color_style() or no_style() in django.core.management.color.
-        """
-        return []
-
-    def sequence_reset_sql(self, style, model_list):
-        """
-        Returns a list of the SQL statements required to reset sequences for
-        the given models.
-
-        The `style` argument is a Style object as returned by either
-        color_style() or no_style() in django.core.management.color.
-        """
-        return []  # No sequence reset required by default.
-
-    def start_transaction_sql(self):
-        """
-        Returns the SQL statement required to start a transaction.
-        """
-        return "BEGIN;"
-
-    def end_transaction_sql(self, success=True):
-        """
-        Returns the SQL statement required to end a transaction.
-        """
-        if not success:
-            return "ROLLBACK;"
-        return "COMMIT;"
-
-    def tablespace_sql(self, tablespace, inline=False):
-        """
-        Returns the SQL that will be used in a query to define the tablespace.
-
-        Returns '' if the backend doesn't support tablespaces.
-
-        If inline is True, the SQL is appended to a row; otherwise it's appended
-        to the entire CREATE TABLE or CREATE INDEX statement.
-        """
-        return ''
-
-    def prep_for_like_query(self, x):
-        """Prepares a value for use in a LIKE query."""
-        from django.utils.encoding import force_text
-        return force_text(x).replace("\\", "\\\\").replace("%", "\%").replace("_", "\_")
-
-    # Same as prep_for_like_query(), but called for "iexact" matches, which
-    # need not necessarily be implemented using "LIKE" in the backend.
-    prep_for_iexact_query = prep_for_like_query
-
-    def validate_autopk_value(self, value):
-        """
-        Certain backends do not accept some values for "serial" fields
-        (for example zero in MySQL). This method will raise a ValueError
-        if the value is invalid, otherwise returns validated value.
-        """
-        return value
-
-    def value_to_db_date(self, value):
-        """
-        Transform a date value to an object compatible with what is expected
-        by the backend driver for date columns.
-        """
-        if value is None:
-            return None
-        return six.text_type(value)
-
-    def value_to_db_datetime(self, value):
-        """
-        Transform a datetime value to an object compatible with what is expected
-        by the backend driver for datetime columns.
-        """
-        if value is None:
-            return None
-        return six.text_type(value)
-
-    def value_to_db_time(self, value):
-        """
-        Transform a time value to an object compatible with what is expected
-        by the backend driver for time columns.
-        """
-        if value is None:
-            return None
-        if timezone.is_aware(value):
-            raise ValueError("Django does not support timezone-aware times.")
-        return six.text_type(value)
-
-    def value_to_db_decimal(self, value, max_digits, decimal_places):
-        """
-        Transform a decimal.Decimal value to an object compatible with what is
-        expected by the backend driver for decimal (numeric) columns.
-        """
-        return utils.format_number(value, max_digits, decimal_places)
-
-    def year_lookup_bounds_for_date_field(self, value):
-        """
-        Returns a two-elements list with the lower and upper bound to be used
-        with a BETWEEN operator to query a DateField value using a year
-        lookup.
-
-        `value` is an int, containing the looked-up year.
-        """
-        first = datetime.date(value, 1, 1)
-        second = datetime.date(value, 12, 31)
-        return [first, second]
-
-    def year_lookup_bounds_for_datetime_field(self, value):
-        """
-        Returns a two-elements list with the lower and upper bound to be used
-        with a BETWEEN operator to query a DateTimeField value using a year
-        lookup.
-
-        `value` is an int, containing the looked-up year.
-        """
-        first = datetime.datetime(value, 1, 1)
-        second = datetime.datetime(value, 12, 31, 23, 59, 59, 999999)
-        if settings.USE_TZ:
-            tz = timezone.get_current_timezone()
-            first = timezone.make_aware(first, tz)
-            second = timezone.make_aware(second, tz)
-        return [first, second]
-
-    def get_db_converters(self, expression):
-        """Get a list of functions needed to convert field data.
-
-        Some field types on some backends do not provide data in the correct
-        format, this is the hook for coverter functions.
-        """
-        return []
-
-    def convert_durationfield_value(self, value, expression, context):
-        if value is not None:
-            value = str(decimal.Decimal(value) / decimal.Decimal(1000000))
-            value = parse_duration(value)
-        return value
-
-    def check_aggregate_support(self, aggregate_func):
-        """Check that the backend supports the provided aggregate
-
-        This is used on specific backends to rule out known aggregates
-        that are known to have faulty implementations. If the named
-        aggregate function has a known problem, the backend should
-        raise NotImplementedError.
-        """
-        pass
-
-    def combine_expression(self, connector, sub_expressions):
-        """Combine a list of subexpressions into a single expression, using
-        the provided connecting operator. This is required because operators
-        can vary between backends (e.g., Oracle with %% and &) and between
-        subexpression types (e.g., date expressions)
-        """
-        conn = ' %s ' % connector
-        return conn.join(sub_expressions)
-
-    def combine_duration_expression(self, connector, sub_expressions):
-        return self.combine_expression(connector, sub_expressions)
-
-    def modify_insert_params(self, placeholders, params):
-        """Allow modification of insert parameters. Needed for Oracle Spatial
-        backend due to #10888.
-        """
-        return params
-
-    def integer_field_range(self, internal_type):
-        """
-        Given an integer field internal type (e.g. 'PositiveIntegerField'),
-        returns a tuple of the (min_value, max_value) form representing the
-        range of the column type bound to the field.
-        """
-        return self.integer_field_ranges[internal_type]
-
-
-class BaseDatabaseIntrospection(object):
-    """
-    This class encapsulates all backend-specific introspection utilities
-    """
-    data_types_reverse = {}
-
-    def __init__(self, connection):
-        self.connection = connection
-
-    def get_field_type(self, data_type, description):
-        """Hook for a database backend to use the cursor description to
-        match a Django field type to a database column.
-
-        For Oracle, the column data_type on its own is insufficient to
-        distinguish between a FloatField and IntegerField, for example."""
-        return self.data_types_reverse[data_type]
-
-    def table_name_converter(self, name):
-        """Apply a conversion to the name for the purposes of comparison.
-
-        The default table name converter is for case sensitive comparison.
-        """
-        return name
-
-    def column_name_converter(self, name):
-        """
-        Apply a conversion to the column name for the purposes of comparison.
-
-        Uses table_name_converter() by default.
-        """
-        return self.table_name_converter(name)
-
-    def table_names(self, cursor=None, include_views=False):
-        """
-        Returns a list of names of all tables that exist in the database.
-        The returned table list is sorted by Python's default sorting. We
-        do NOT use database's ORDER BY here to avoid subtle differences
-        in sorting order between databases.
-        """
-        def get_names(cursor):
-            return sorted(ti.name for ti in self.get_table_list(cursor)
-                          if include_views or ti.type == 't')
-        if cursor is None:
-            with self.connection.cursor() as cursor:
-                return get_names(cursor)
-        return get_names(cursor)
-
-    def get_table_list(self, cursor):
-        """
-        Returns an unsorted list of TableInfo named tuples of all tables and
-        views that exist in the database.
-        """
-        raise NotImplementedError('subclasses of BaseDatabaseIntrospection may require a get_table_list() method')
-
-    def django_table_names(self, only_existing=False, include_views=True):
-        """
-        Returns a list of all table names that have associated Django models and
-        are in INSTALLED_APPS.
-
-        If only_existing is True, the resulting list will only include the tables
-        that actually exist in the database.
-        """
-        from django.apps import apps
-        from django.db import router
-        tables = set()
-        for app_config in apps.get_app_configs():
-            for model in router.get_migratable_models(app_config, self.connection.alias):
-                if not model._meta.managed:
-                    continue
-                tables.add(model._meta.db_table)
-                tables.update(f.m2m_db_table() for f in model._meta.local_many_to_many)
-        tables = list(tables)
-        if only_existing:
-            existing_tables = self.table_names(include_views=include_views)
-            tables = [
-                t
-                for t in tables
-                if self.table_name_converter(t) in existing_tables
-            ]
-        return tables
-
-    def installed_models(self, tables):
-        "Returns a set of all models represented by the provided list of table names."
-        from django.apps import apps
-        from django.db import router
-        all_models = []
-        for app_config in apps.get_app_configs():
-            all_models.extend(router.get_migratable_models(app_config, self.connection.alias))
-        tables = list(map(self.table_name_converter, tables))
-        return {
-            m for m in all_models
-            if self.table_name_converter(m._meta.db_table) in tables
-        }
-
-    def sequence_list(self):
-        "Returns a list of information about all DB sequences for all models in all apps."
-        from django.apps import apps
-        from django.db import models, router
-
-        sequence_list = []
-
-        for app_config in apps.get_app_configs():
-            for model in router.get_migratable_models(app_config, self.connection.alias):
-                if not model._meta.managed:
-                    continue
-                if model._meta.swapped:
-                    continue
-                for f in model._meta.local_fields:
-                    if isinstance(f, models.AutoField):
-                        sequence_list.append({'table': model._meta.db_table, 'column': f.column})
-                        break  # Only one AutoField is allowed per model, so don't bother continuing.
-
-                for f in model._meta.local_many_to_many:
-                    # If this is an m2m using an intermediate table,
-                    # we don't need to reset the sequence.
-                    if f.rel.through is None:
-                        sequence_list.append({'table': f.m2m_db_table(), 'column': None})
-
-        return sequence_list
-
-    def get_key_columns(self, cursor, table_name):
-        """
-        Backends can override this to return a list of (column_name, referenced_table_name,
-        referenced_column_name) for all key columns in given table.
-        """
-        raise NotImplementedError('subclasses of BaseDatabaseIntrospection may require a get_key_columns() method')
-
-    def get_primary_key_column(self, cursor, table_name):
-        """
-        Returns the name of the primary key column for the given table.
-        """
-        for column in six.iteritems(self.get_indexes(cursor, table_name)):
-            if column[1]['primary_key']:
-                return column[0]
-        return None
-
-    def get_indexes(self, cursor, table_name):
-        """
-        Returns a dictionary of indexed fieldname -> infodict for the given
-        table, where each infodict is in the format:
-            {'primary_key': boolean representing whether it's the primary key,
-             'unique': boolean representing whether it's a unique index}
-
-        Only single-column indexes are introspected.
-        """
-        raise NotImplementedError('subclasses of BaseDatabaseIntrospection may require a get_indexes() method')
-
-    def get_constraints(self, cursor, table_name):
-        """
-        Retrieves any constraints or keys (unique, pk, fk, check, index)
-        across one or more columns.
-
-        Returns a dict mapping constraint names to their attributes,
-        where attributes is a dict with keys:
-         * columns: List of columns this covers
-         * primary_key: True if primary key, False otherwise
-         * unique: True if this is a unique constraint, False otherwise
-         * foreign_key: (table, column) of target, or None
-         * check: True if check constraint, False otherwise
-         * index: True if index, False otherwise.
-
-        Some backends may return special constraint names that don't exist
-        if they don't name constraints of a certain type (e.g. SQLite)
-        """
-        raise NotImplementedError('subclasses of BaseDatabaseIntrospection may require a get_constraints() method')
-
-
-class BaseDatabaseClient(object):
-    """
-    This class encapsulates all backend-specific methods for opening a
-    client shell.
-    """
-    # This should be a string representing the name of the executable
-    # (e.g., "psql"). Subclasses must override this.
-    executable_name = None
-
-    def __init__(self, connection):
-        # connection is an instance of BaseDatabaseWrapper.
-        self.connection = connection
-
-    def runshell(self):
-        raise NotImplementedError('subclasses of BaseDatabaseClient must provide a runshell() method')
-
-
-class BaseDatabaseValidation(object):
-    """
-    This class encapsulates all backend-specific model validation.
-    """
-    def __init__(self, connection):
-        self.connection = connection
-
-    def validate_field(self, errors, opts, f):
-        """
-        By default, there is no backend-specific validation.
-
-        This method has been deprecated by the new checks framework. New
-        backends should implement check_field instead.
-        """
-        # This is deliberately commented out. It exists as a marker to
-        # remind us to remove this method, and the check_field() shim,
-        # when the time comes.
-        # warnings.warn('"validate_field" has been deprecated", RemovedInDjango19Warning)
-        pass
-
-    def check_field(self, field, **kwargs):
-        class ErrorList(list):
-            """A dummy list class that emulates API used by the older
-            validate_field() method. When validate_field() is fully
-            deprecated, this dummy can be removed too.
-            """
-            def add(self, opts, error_message):
-                self.append(checks.Error(error_message, hint=None, obj=field))
-
-        errors = ErrorList()
-        # Some tests create fields in isolation -- the fields are not attached
-        # to any model, so they have no `model` attribute.
-        opts = field.model._meta if hasattr(field, 'model') else None
-        self.validate_field(errors, field, opts)
-        return list(errors)

django/db/backends/base/base.py

@@ -0,0 +1,507 @@
+from collections import deque
+from contextlib import contextmanager
+import time
+import warnings
+
+from django.conf import settings
+from django.db import DEFAULT_DB_ALIAS
+from django.db.backends.signals import connection_created
+from django.db.backends import utils
+from django.db.transaction import TransactionManagementError
+from django.db.utils import DatabaseError, DatabaseErrorWrapper
+from django.utils.functional import cached_property
+try:
+    from django.utils.six.moves import _thread as thread
+except ImportError:
+    from django.utils.six.moves import _dummy_thread as thread
+
+
+NO_DB_ALIAS = '__no_db__'
+
+
+class BaseDatabaseWrapper(object):
+    """
+    Represents a database connection.
+    """
+    # Mapping of Field objects to their column types.
+    data_types = {}
+    # Mapping of Field objects to their SQL suffix such as AUTOINCREMENT.
+    data_types_suffix = {}
+    # Mapping of Field objects to their SQL for CHECK constraints.
+    data_type_check_constraints = {}
+    ops = None
+    vendor = 'unknown'
+    SchemaEditorClass = None
+
+    queries_limit = 9000
+
+    def __init__(self, settings_dict, alias=DEFAULT_DB_ALIAS,
+                 allow_thread_sharing=False):
+        # Connection related attributes.
+        # The underlying database connection.
+        self.connection = None
+        # `settings_dict` should be a dictionary containing keys such as
+        # NAME, USER, etc. It's called `settings_dict` instead of `settings`
+        # to disambiguate it from Django settings modules.
+        self.settings_dict = settings_dict
+        self.alias = alias
+        # Query logging in debug mode or when explicitly enabled.
+        self.queries_log = deque(maxlen=self.queries_limit)
+        self.force_debug_cursor = False
+
+        # Transaction related attributes.
+        # Tracks if the connection is in autocommit mode. Per PEP 249, by
+        # default, it isn't.
+        self.autocommit = False
+        # Tracks if the connection is in a transaction managed by 'atomic'.
+        self.in_atomic_block = False
+        # Increment to generate unique savepoint ids.
+        self.savepoint_state = 0
+        # List of savepoints created by 'atomic'.
+        self.savepoint_ids = []
+        # Tracks if the outermost 'atomic' block should commit on exit,
+        # ie. if autocommit was active on entry.
+        self.commit_on_exit = True
+        # Tracks if the transaction should be rolled back to the next
+        # available savepoint because of an exception in an inner block.
+        self.needs_rollback = False
+
+        # Connection termination related attributes.
+        self.close_at = None
+        self.closed_in_transaction = False
+        self.errors_occurred = False
+
+        # Thread-safety related attributes.
+        self.allow_thread_sharing = allow_thread_sharing
+        self._thread_ident = thread.get_ident()
+
+    @property
+    def queries_logged(self):
+        return self.force_debug_cursor or settings.DEBUG
+
+    @property
+    def queries(self):
+        if len(self.queries_log) == self.queries_log.maxlen:
+            warnings.warn(
+                "Limit for query logging exceeded, only the last {} queries "
+                "will be returned.".format(self.queries_log.maxlen))
+        return list(self.queries_log)
+
+    ##### Backend-specific methods for creating connections and cursors #####
+
+    def get_connection_params(self):
+        """Returns a dict of parameters suitable for get_new_connection."""
+        raise NotImplementedError('subclasses of BaseDatabaseWrapper may require a get_connection_params() method')
+
+    def get_new_connection(self, conn_params):
+        """Opens a connection to the database."""
+        raise NotImplementedError('subclasses of BaseDatabaseWrapper may require a get_new_connection() method')
+
+    def init_connection_state(self):
+        """Initializes the database connection settings."""
+        raise NotImplementedError('subclasses of BaseDatabaseWrapper may require an init_connection_state() method')
+
+    def create_cursor(self):
+        """Creates a cursor. Assumes that a connection is established."""
+        raise NotImplementedError('subclasses of BaseDatabaseWrapper may require a create_cursor() method')
+
+    ##### Backend-specific methods for creating connections #####
+
+    def connect(self):
+        """Connects to the database. Assumes that the connection is closed."""
+        # In case the previous connection was closed while in an atomic block
+        self.in_atomic_block = False
+        self.savepoint_ids = []
+        self.needs_rollback = False
+        # Reset parameters defining when to close the connection
+        max_age = self.settings_dict['CONN_MAX_AGE']
+        self.close_at = None if max_age is None else time.time() + max_age
+        self.closed_in_transaction = False
+        self.errors_occurred = False
+        # Establish the connection
+        conn_params = self.get_connection_params()
+        self.connection = self.get_new_connection(conn_params)
+        self.set_autocommit(self.settings_dict['AUTOCOMMIT'])
+        self.init_connection_state()
+        connection_created.send(sender=self.__class__, connection=self)
+
+    def ensure_connection(self):
+        """
+        Guarantees that a connection to the database is established.
+        """
+        if self.connection is None:
+            with self.wrap_database_errors:
+                self.connect()
+
+    ##### Backend-specific wrappers for PEP-249 connection methods #####
+
+    def _cursor(self):
+        self.ensure_connection()
+        with self.wrap_database_errors:
+            return self.create_cursor()
+
+    def _commit(self):
+        if self.connection is not None:
+            with self.wrap_database_errors:
+                return self.connection.commit()
+
+    def _rollback(self):
+        if self.connection is not None:
+            with self.wrap_database_errors:
+                return self.connection.rollback()
+
+    def _close(self):
+        if self.connection is not None:
+            with self.wrap_database_errors:
+                return self.connection.close()
+
+    ##### Generic wrappers for PEP-249 connection methods #####
+
+    def cursor(self):
+        """
+        Creates a cursor, opening a connection if necessary.
+        """
+        self.validate_thread_sharing()
+        if self.queries_logged:
+            cursor = self.make_debug_cursor(self._cursor())
+        else:
+            cursor = self.make_cursor(self._cursor())
+        return cursor
+
+    def commit(self):
+        """
+        Commits a transaction and resets the dirty flag.
+        """
+        self.validate_thread_sharing()
+        self.validate_no_atomic_block()
+        self._commit()
+        # A successful commit means that the database connection works.
+        self.errors_occurred = False
+
+    def rollback(self):
+        """
+        Rolls back a transaction and resets the dirty flag.
+        """
+        self.validate_thread_sharing()
+        self.validate_no_atomic_block()
+        self._rollback()
+        # A successful rollback means that the database connection works.
+        self.errors_occurred = False
+
+    def close(self):
+        """
+        Closes the connection to the database.
+        """
+        self.validate_thread_sharing()
+        # Don't call validate_no_atomic_block() to avoid making it difficult
+        # to get rid of a connection in an invalid state. The next connect()
+        # will reset the transaction state anyway.
+        if self.closed_in_transaction or self.connection is None:
+            return
+        try:
+            self._close()
+        finally:
+            if self.in_atomic_block:
+                self.closed_in_transaction = True
+                self.needs_rollback = True
+            else:
+                self.connection = None
+
+    ##### Backend-specific savepoint management methods #####
+
+    def _savepoint(self, sid):
+        with self.cursor() as cursor:
+            cursor.execute(self.ops.savepoint_create_sql(sid))
+
+    def _savepoint_rollback(self, sid):
+        with self.cursor() as cursor:
+            cursor.execute(self.ops.savepoint_rollback_sql(sid))
+
+    def _savepoint_commit(self, sid):
+        with self.cursor() as cursor:
+            cursor.execute(self.ops.savepoint_commit_sql(sid))
+
+    def _savepoint_allowed(self):
+        # Savepoints cannot be created outside a transaction
+        return self.features.uses_savepoints and not self.get_autocommit()
+
+    ##### Generic savepoint management methods #####
+
+    def savepoint(self):
+        """
+        Creates a savepoint inside the current transaction. Returns an
+        identifier for the savepoint that will be used for the subsequent
+        rollback or commit. Does nothing if savepoints are not supported.
+        """
+        if not self._savepoint_allowed():
+            return
+
+        thread_ident = thread.get_ident()
+        tid = str(thread_ident).replace('-', '')
+
+        self.savepoint_state += 1
+        sid = "s%s_x%d" % (tid, self.savepoint_state)
+
+        self.validate_thread_sharing()
+        self._savepoint(sid)
+
+        return sid
+
+    def savepoint_rollback(self, sid):
+        """
+        Rolls back to a savepoint. Does nothing if savepoints are not supported.
+        """
+        if not self._savepoint_allowed():
+            return
+
+        self.validate_thread_sharing()
+        self._savepoint_rollback(sid)
+
+    def savepoint_commit(self, sid):
+        """
+        Releases a savepoint. Does nothing if savepoints are not supported.
+        """
+        if not self._savepoint_allowed():
+            return
+
+        self.validate_thread_sharing()
+        self._savepoint_commit(sid)
+
+    def clean_savepoints(self):
+        """
+        Resets the counter used to generate unique savepoint ids in this thread.
+        """
+        self.savepoint_state = 0
+
+    ##### Backend-specific transaction management methods #####
+
+    def _set_autocommit(self, autocommit):
+        """
+        Backend-specific implementation to enable or disable autocommit.
+        """
+        raise NotImplementedError('subclasses of BaseDatabaseWrapper may require a _set_autocommit() method')
+
+    ##### Generic transaction management methods #####
+
+    def get_autocommit(self):
+        """
+        Check the autocommit state.
+        """
+        self.ensure_connection()
+        return self.autocommit
+
+    def set_autocommit(self, autocommit):
+        """
+        Enable or disable autocommit.
+        """
+        self.validate_no_atomic_block()
+        self.ensure_connection()
+        self._set_autocommit(autocommit)
+        self.autocommit = autocommit
+
+    def get_rollback(self):
+        """
+        Get the "needs rollback" flag -- for *advanced use* only.
+        """
+        if not self.in_atomic_block:
+            raise TransactionManagementError(
+                "The rollback flag doesn't work outside of an 'atomic' block.")
+        return self.needs_rollback
+
+    def set_rollback(self, rollback):
+        """
+        Set or unset the "needs rollback" flag -- for *advanced use* only.
+        """
+        if not self.in_atomic_block:
+            raise TransactionManagementError(
+                "The rollback flag doesn't work outside of an 'atomic' block.")
+        self.needs_rollback = rollback
+
+    def validate_no_atomic_block(self):
+        """
+        Raise an error if an atomic block is active.
+        """
+        if self.in_atomic_block:
+            raise TransactionManagementError(
+                "This is forbidden when an 'atomic' block is active.")
+
+    def validate_no_broken_transaction(self):
+        if self.needs_rollback:
+            raise TransactionManagementError(
+                "An error occurred in the current transaction. You can't "
+                "execute queries until the end of the 'atomic' block.")
+
+    ##### Foreign key constraints checks handling #####
+
+    @contextmanager
+    def constraint_checks_disabled(self):
+        """
+        Context manager that disables foreign key constraint checking.
+        """
+        disabled = self.disable_constraint_checking()
+        try:
+            yield
+        finally:
+            if disabled:
+                self.enable_constraint_checking()
+
+    def disable_constraint_checking(self):
+        """
+        Backends can implement as needed to temporarily disable foreign key
+        constraint checking. Should return True if the constraints were
+        disabled and will need to be reenabled.
+        """
+        return False
+
+    def enable_constraint_checking(self):
+        """
+        Backends can implement as needed to re-enable foreign key constraint
+        checking.
+        """
+        pass
+
+    def check_constraints(self, table_names=None):
+        """
+        Backends can override this method if they can apply constraint
+        checking (e.g. via "SET CONSTRAINTS ALL IMMEDIATE"). Should raise an
+        IntegrityError if any invalid foreign key references are encountered.
+        """
+        pass
+
+    ##### Connection termination handling #####
+
+    def is_usable(self):
+        """
+        Tests if the database connection is usable.
+
+        This function may assume that self.connection is not None.
+
+        Actual implementations should take care not to raise exceptions
+        as that may prevent Django from recycling unusable connections.
+        """
+        raise NotImplementedError(
+            "subclasses of BaseDatabaseWrapper may require an is_usable() method")
+
+    def close_if_unusable_or_obsolete(self):
+        """
+        Closes the current connection if unrecoverable errors have occurred,
+        or if it outlived its maximum age.
+        """
+        if self.connection is not None:
+            # If the application didn't restore the original autocommit setting,
+            # don't take chances, drop the connection.
+            if self.get_autocommit() != self.settings_dict['AUTOCOMMIT']:
+                self.close()
+                return
+
+            # If an exception other than DataError or IntegrityError occurred
+            # since the last commit / rollback, check if the connection works.
+            if self.errors_occurred:
+                if self.is_usable():
+                    self.errors_occurred = False
+                else:
+                    self.close()
+                    return
+
+            if self.close_at is not None and time.time() >= self.close_at:
+                self.close()
+                return
+
+    ##### Thread safety handling #####
+
+    def validate_thread_sharing(self):
+        """
+        Validates that the connection isn't accessed by another thread than the
+        one which originally created it, unless the connection was explicitly
+        authorized to be shared between threads (via the `allow_thread_sharing`
+        property). Raises an exception if the validation fails.
+        """
+        if not (self.allow_thread_sharing
+                or self._thread_ident == thread.get_ident()):
+            raise DatabaseError("DatabaseWrapper objects created in a "
+                "thread can only be used in that same thread. The object "
+                "with alias '%s' was created in thread id %s and this is "
+                "thread id %s."
+                % (self.alias, self._thread_ident, thread.get_ident()))
+
+    ##### Miscellaneous #####
+
+    def prepare_database(self):
+        """
+        Hook to do any database check or preparation, generally called before
+        migrating a project or an app.
+        """
+        pass
+
+    @cached_property
+    def wrap_database_errors(self):
+        """
+        Context manager and decorator that re-throws backend-specific database
+        exceptions using Django's common wrappers.
+        """
+        return DatabaseErrorWrapper(self)
+
+    def make_debug_cursor(self, cursor):
+        """
+        Creates a cursor that logs all queries in self.queries_log.
+        """
+        return utils.CursorDebugWrapper(cursor, self)
+
+    def make_cursor(self, cursor):
+        """
+        Creates a cursor without debug logging.
+        """
+        return utils.CursorWrapper(cursor, self)
+
+    @contextmanager
+    def temporary_connection(self):
+        """
+        Context manager that ensures that a connection is established, and
+        if it opened one, closes it to avoid leaving a dangling connection.
+        This is useful for operations outside of the request-response cycle.
+
+        Provides a cursor: with self.temporary_connection() as cursor: ...
+        """
+        must_close = self.connection is None
+        cursor = self.cursor()
+        try:
+            yield cursor
+        finally:
+            cursor.close()
+            if must_close:
+                self.close()
+
+    @cached_property
+    def _nodb_connection(self):
+        """
+        Alternative connection to be used when there is no need to access
+        the main database, specifically for test db creation/deletion.
+        This also prevents the production database from being exposed to
+        potential child threads while (or after) the test database is destroyed.
+        Refs #10868, #17786, #16969.
+        """
+        settings_dict = self.settings_dict.copy()
+        settings_dict['NAME'] = None
+        nodb_connection = self.__class__(
+            settings_dict,
+            alias=NO_DB_ALIAS,
+            allow_thread_sharing=False)
+        return nodb_connection
+
+    def _start_transaction_under_autocommit(self):
+        """
+        Only required when autocommits_when_autocommit_is_off = True.
+        """
+        raise NotImplementedError(
+            'subclasses of BaseDatabaseWrapper may require a '
+            '_start_transaction_under_autocommit() method'
+        )
+
+    def schema_editor(self, *args, **kwargs):
+        """
+        Returns a new instance of this backend's SchemaEditor.
+        """
+        if self.SchemaEditorClass is None:
+            raise NotImplementedError(
+                'The SchemaEditorClass attribute of this database wrapper is still None')
+        return self.SchemaEditorClass(self, *args, **kwargs)

django/db/backends/base/client.py

@@ -0,0 +1,15 @@
+class BaseDatabaseClient(object):
+    """
+    This class encapsulates all backend-specific methods for opening a
+    client shell.
+    """
+    # This should be a string representing the name of the executable
+    # (e.g., "psql"). Subclasses must override this.
+    executable_name = None
+
+    def __init__(self, connection):
+        # connection is an instance of BaseDatabaseWrapper.
+        self.connection = connection
+
+    def runshell(self):
+        raise NotImplementedError('subclasses of BaseDatabaseClient must provide a runshell() method')

django/db/backends/creation.py → django/db/backends/base/creation.py

@@ -3,16 +3,16 @@ import sys
 import time
 import warnings
 
+from django.apps import apps
 from django.conf import settings
+from django.core import serializers
+from django.db import router
+from django.db.backends.utils import truncate_name
 from django.utils.deprecation import RemovedInDjango20Warning
 from django.utils.encoding import force_bytes
-from django.utils.six.moves import input
 from django.utils.six import StringIO
-from django.db import router
-from django.apps import apps
-from django.core import serializers
+from django.utils.six.moves import input
 
-from .utils import truncate_name
 
 # The prefix to put on the default database name when creating
 # the test database.

django/db/backends/base/features.py

@@ -0,0 +1,250 @@
+from django.db.utils import ProgrammingError
+from django.utils.functional import cached_property
+
+
+class BaseDatabaseFeatures(object):
+    gis_enabled = False
+    allows_group_by_pk = False
+    # True if django.db.backends.utils.typecast_timestamp is used on values
+    # returned from dates() calls.
+    needs_datetime_string_cast = True
+    empty_fetchmany_value = []
+    update_can_self_select = True
+
+    # Does the backend distinguish between '' and None?
+    interprets_empty_strings_as_nulls = False
+
+    # Does the backend allow inserting duplicate NULL rows in a nullable
+    # unique field? All core backends implement this correctly, but other
+    # databases such as SQL Server do not.
+    supports_nullable_unique_constraints = True
+
+    # Does the backend allow inserting duplicate rows when a unique_together
+    # constraint exists and some fields are nullable but not all of them?
+    supports_partially_nullable_unique_constraints = True
+
+    can_use_chunked_reads = True
+    can_return_id_from_insert = False
+    has_bulk_insert = False
+    uses_savepoints = False
+    can_release_savepoints = False
+    can_combine_inserts_with_and_without_auto_increment_pk = False
+
+    # If True, don't use integer foreign keys referring to, e.g., positive
+    # integer primary keys.
+    related_fields_match_type = False
+    allow_sliced_subqueries = True
+    has_select_for_update = False
+    has_select_for_update_nowait = False
+
+    supports_select_related = True
+
+    # Does the default test database allow multiple connections?
+    # Usually an indication that the test database is in-memory
+    test_db_allows_multiple_connections = True
+
+    # Can an object be saved without an explicit primary key?
+    supports_unspecified_pk = False
+
+    # Can a fixture contain forward references? i.e., are
+    # FK constraints checked at the end of transaction, or
+    # at the end of each save operation?
+    supports_forward_references = True
+
+    # Does the backend truncate names properly when they are too long?
+    truncates_names = False
+
+    # Is there a REAL datatype in addition to floats/doubles?
+    has_real_datatype = False
+    supports_subqueries_in_group_by = True
+    supports_bitwise_or = True
+
+    # Is there a true datatype for timedeltas?
+    has_native_duration_field = False
+
+    # Does the database driver support timedeltas as arguments?
+    # This is only relevant when there is a native duration field.
+    # Specifically, there is a bug with cx_Oracle:
+    # https://bitbucket.org/anthony_tuininga/cx_oracle/issue/7/
+    driver_supports_timedelta_args = False
+
+    # Do time/datetime fields have microsecond precision?
+    supports_microsecond_precision = True
+
+    # Does the __regex lookup support backreferencing and grouping?
+    supports_regex_backreferencing = True
+
+    # Can date/datetime lookups be performed using a string?
+    supports_date_lookup_using_string = True
+
+    # Can datetimes with timezones be used?
+    supports_timezones = True
+
+    # Does the database have a copy of the zoneinfo database?
+    has_zoneinfo_database = True
+
+    # When performing a GROUP BY, is an ORDER BY NULL required
+    # to remove any ordering?
+    requires_explicit_null_ordering_when_grouping = False
+
+    # Does the backend order NULL values as largest or smallest?
+    nulls_order_largest = False
+
+    # Is there a 1000 item limit on query parameters?
+    supports_1000_query_parameters = True
+
+    # Can an object have an autoincrement primary key of 0? MySQL says No.
+    allows_auto_pk_0 = True
+
+    # Do we need to NULL a ForeignKey out, or can the constraint check be
+    # deferred
+    can_defer_constraint_checks = False
+
+    # date_interval_sql can properly handle mixed Date/DateTime fields and timedeltas
+    supports_mixed_date_datetime_comparisons = True
+
+    # Does the backend support tablespaces? Default to False because it isn't
+    # in the SQL standard.
+    supports_tablespaces = False
+
+    # Does the backend reset sequences between tests?
+    supports_sequence_reset = True
+
+    # Can the backend determine reliably the length of a CharField?
+    can_introspect_max_length = True
+
+    # Can the backend determine reliably if a field is nullable?
+    # Note that this is separate from interprets_empty_strings_as_nulls,
+    # although the latter feature, when true, interferes with correct
+    # setting (and introspection) of CharFields' nullability.
+    # This is True for all core backends.
+    can_introspect_null = True
+
+    # Confirm support for introspected foreign keys
+    # Every database can do this reliably, except MySQL,
+    # which can't do it for MyISAM tables
+    can_introspect_foreign_keys = True
+
+    # Can the backend introspect an AutoField, instead of an IntegerField?
+    can_introspect_autofield = False
+
+    # Can the backend introspect a BigIntegerField, instead of an IntegerField?
+    can_introspect_big_integer_field = True
+
+    # Can the backend introspect an BinaryField, instead of an TextField?
+    can_introspect_binary_field = True
+
+    # Can the backend introspect an DecimalField, instead of an FloatField?
+    can_introspect_decimal_field = True
+
+    # Can the backend introspect an IPAddressField, instead of an CharField?
+    can_introspect_ip_address_field = False
+
+    # Can the backend introspect a PositiveIntegerField, instead of an IntegerField?
+    can_introspect_positive_integer_field = False
+
+    # Can the backend introspect a SmallIntegerField, instead of an IntegerField?
+    can_introspect_small_integer_field = False
+
+    # Can the backend introspect a TimeField, instead of a DateTimeField?
+    can_introspect_time_field = True
+
+    # Support for the DISTINCT ON clause
+    can_distinct_on_fields = False
+
+    # Does the backend decide to commit before SAVEPOINT statements
+    # when autocommit is disabled? http://bugs.python.org/issue8145#msg109965
+    autocommits_when_autocommit_is_off = False
+
+    # Does the backend prevent running SQL queries in broken transactions?
+    atomic_transactions = True
+
+    # Can we roll back DDL in a transaction?
+    can_rollback_ddl = False
+
+    # Can we issue more than one ALTER COLUMN clause in an ALTER TABLE?
+    supports_combined_alters = False
+
+    # Does it support foreign keys?
+    supports_foreign_keys = True
+
+    # Does it support CHECK constraints?
+    supports_column_check_constraints = True
+
+    # Does the backend support 'pyformat' style ("... %(name)s ...", {'name': value})
+    # parameter passing? Note this can be provided by the backend even if not
+    # supported by the Python driver
+    supports_paramstyle_pyformat = True
+
+    # Does the backend require literal defaults, rather than parameterized ones?
+    requires_literal_defaults = False
+
+    # Does the backend require a connection reset after each material schema change?
+    connection_persists_old_columns = False
+
+    # What kind of error does the backend throw when accessing closed cursor?
+    closed_cursor_error_class = ProgrammingError
+
+    # Does 'a' LIKE 'A' match?
+    has_case_insensitive_like = True
+
+    # Does the backend require the sqlparse library for splitting multi-line
+    # statements before executing them?
+    requires_sqlparse_for_splitting = True
+
+    # Suffix for backends that don't support "SELECT xxx;" queries.
+    bare_select_suffix = ''
+
+    # If NULL is implied on columns without needing to be explicitly specified
+    implied_column_null = False
+
+    uppercases_column_names = False
+
+    # Does the backend support "select for update" queries with limit (and offset)?
+    supports_select_for_update_with_limit = True
+
+    def __init__(self, connection):
+        self.connection = connection
+
+    @cached_property
+    def supports_transactions(self):
+        """Confirm support for transactions."""
+        with self.connection.cursor() as cursor:
+            cursor.execute('CREATE TABLE ROLLBACK_TEST (X INT)')
+            self.connection.set_autocommit(False)
+            cursor.execute('INSERT INTO ROLLBACK_TEST (X) VALUES (8)')
+            self.connection.rollback()
+            self.connection.set_autocommit(True)
+            cursor.execute('SELECT COUNT(X) FROM ROLLBACK_TEST')
+            count, = cursor.fetchone()
+            cursor.execute('DROP TABLE ROLLBACK_TEST')
+        return count == 0
+
+    @cached_property
+    def supports_stddev(self):
+        """Confirm support for STDDEV and related stats functions."""
+        class StdDevPop(object):
+            sql_function = 'STDDEV_POP'
+
+        try:
+            self.connection.ops.check_aggregate_support(StdDevPop())
+            return True
+        except NotImplementedError:
+            return False
+
+    def introspected_boolean_field_type(self, field=None, created_separately=False):
+        """
+        What is the type returned when the backend introspects a BooleanField?
+        The optional arguments may be used to give further details of the field to be
+        introspected; in particular, they are provided by Django's test suite:
+        field -- the field definition
+        created_separately -- True if the field was added via a SchemaEditor's AddField,
+                              False if the field was created with the model
+
+        Note that return value from this function is compared by tests against actual
+        introspection results; it should provide expectations, not run an introspection
+        itself.
+        """
+        if self.can_introspect_null and field and field.null:
+            return 'NullBooleanField'
+        return 'BooleanField'

django/db/backends/base/introspection.py

@@ -0,0 +1,178 @@
+from collections import namedtuple
+
+from django.utils import six
+
+
+# Structure returned by DatabaseIntrospection.get_table_list()
+TableInfo = namedtuple('TableInfo', ['name', 'type'])
+
+# Structure returned by the DB-API cursor.description interface (PEP 249)
+FieldInfo = namedtuple('FieldInfo',
+    'name type_code display_size internal_size precision scale null_ok')
+
+
+class BaseDatabaseIntrospection(object):
+    """
+    This class encapsulates all backend-specific introspection utilities
+    """
+    data_types_reverse = {}
+
+    def __init__(self, connection):
+        self.connection = connection
+
+    def get_field_type(self, data_type, description):
+        """Hook for a database backend to use the cursor description to
+        match a Django field type to a database column.
+
+        For Oracle, the column data_type on its own is insufficient to
+        distinguish between a FloatField and IntegerField, for example."""
+        return self.data_types_reverse[data_type]
+
+    def table_name_converter(self, name):
+        """Apply a conversion to the name for the purposes of comparison.
+
+        The default table name converter is for case sensitive comparison.
+        """
+        return name
+
+    def column_name_converter(self, name):
+        """
+        Apply a conversion to the column name for the purposes of comparison.
+
+        Uses table_name_converter() by default.
+        """
+        return self.table_name_converter(name)
+
+    def table_names(self, cursor=None, include_views=False):
+        """
+        Returns a list of names of all tables that exist in the database.
+        The returned table list is sorted by Python's default sorting. We
+        do NOT use database's ORDER BY here to avoid subtle differences
+        in sorting order between databases.
+        """
+        def get_names(cursor):
+            return sorted(ti.name for ti in self.get_table_list(cursor)
+                          if include_views or ti.type == 't')
+        if cursor is None:
+            with self.connection.cursor() as cursor:
+                return get_names(cursor)
+        return get_names(cursor)
+
+    def get_table_list(self, cursor):
+        """
+        Returns an unsorted list of TableInfo named tuples of all tables and
+        views that exist in the database.
+        """
+        raise NotImplementedError('subclasses of BaseDatabaseIntrospection may require a get_table_list() method')
+
+    def django_table_names(self, only_existing=False, include_views=True):
+        """
+        Returns a list of all table names that have associated Django models and
+        are in INSTALLED_APPS.
+
+        If only_existing is True, the resulting list will only include the tables
+        that actually exist in the database.
+        """
+        from django.apps import apps
+        from django.db import router
+        tables = set()
+        for app_config in apps.get_app_configs():
+            for model in router.get_migratable_models(app_config, self.connection.alias):
+                if not model._meta.managed:
+                    continue
+                tables.add(model._meta.db_table)
+                tables.update(f.m2m_db_table() for f in model._meta.local_many_to_many)
+        tables = list(tables)
+        if only_existing:
+            existing_tables = self.table_names(include_views=include_views)
+            tables = [
+                t
+                for t in tables
+                if self.table_name_converter(t) in existing_tables
+            ]
+        return tables
+
+    def installed_models(self, tables):
+        "Returns a set of all models represented by the provided list of table names."
+        from django.apps import apps
+        from django.db import router
+        all_models = []
+        for app_config in apps.get_app_configs():
+            all_models.extend(router.get_migratable_models(app_config, self.connection.alias))
+        tables = list(map(self.table_name_converter, tables))
+        return {
+            m for m in all_models
+            if self.table_name_converter(m._meta.db_table) in tables
+        }
+
+    def sequence_list(self):
+        "Returns a list of information about all DB sequences for all models in all apps."
+        from django.apps import apps
+        from django.db import models, router
+
+        sequence_list = []
+
+        for app_config in apps.get_app_configs():
+            for model in router.get_migratable_models(app_config, self.connection.alias):
+                if not model._meta.managed:
+                    continue
+                if model._meta.swapped:
+                    continue
+                for f in model._meta.local_fields:
+                    if isinstance(f, models.AutoField):
+                        sequence_list.append({'table': model._meta.db_table, 'column': f.column})
+                        break  # Only one AutoField is allowed per model, so don't bother continuing.
+
+                for f in model._meta.local_many_to_many:
+                    # If this is an m2m using an intermediate table,
+                    # we don't need to reset the sequence.
+                    if f.rel.through is None:
+                        sequence_list.append({'table': f.m2m_db_table(), 'column': None})
+
+        return sequence_list
+
+    def get_key_columns(self, cursor, table_name):
+        """
+        Backends can override this to return a list of (column_name, referenced_table_name,
+        referenced_column_name) for all key columns in given table.
+        """
+        raise NotImplementedError('subclasses of BaseDatabaseIntrospection may require a get_key_columns() method')
+
+    def get_primary_key_column(self, cursor, table_name):
+        """
+        Returns the name of the primary key column for the given table.
+        """
+        for column in six.iteritems(self.get_indexes(cursor, table_name)):
+            if column[1]['primary_key']:
+                return column[0]
+        return None
+
+    def get_indexes(self, cursor, table_name):
+        """
+        Returns a dictionary of indexed fieldname -> infodict for the given
+        table, where each infodict is in the format:
+            {'primary_key': boolean representing whether it's the primary key,
+             'unique': boolean representing whether it's a unique index}
+
+        Only single-column indexes are introspected.
+        """
+        raise NotImplementedError('subclasses of BaseDatabaseIntrospection may require a get_indexes() method')
+
+    def get_constraints(self, cursor, table_name):
+        """
+        Retrieves any constraints or keys (unique, pk, fk, check, index)
+        across one or more columns.
+
+        Returns a dict mapping constraint names to their attributes,
+        where attributes is a dict with keys:
+         * columns: List of columns this covers
+         * primary_key: True if primary key, False otherwise
+         * unique: True if this is a unique constraint, False otherwise
+         * foreign_key: (table, column) of target, or None
+         * check: True if check constraint, False otherwise
+         * index: True if index, False otherwise.
+
+        Some backends may return special constraint names that don't exist
+        if they don't name constraints of a certain type (e.g. SQLite)
+        """
+        raise NotImplementedError('subclasses of BaseDatabaseIntrospection may require a get_constraints() method')

django/db/backends/base/operations.py

@@ -0,0 +1,555 @@
+import datetime
+import decimal
+from importlib import import_module
+import warnings
+
+from django.conf import settings
+from django.db.backends import utils
+from django.utils import six, timezone
+from django.utils.dateparse import parse_duration
+from django.utils.deprecation import RemovedInDjango19Warning
+from django.utils.encoding import force_text
+
+
+class BaseDatabaseOperations(object):
+    """
+    This class encapsulates all backend-specific differences, such as the way
+    a backend performs ordering or calculates the ID of a recently-inserted
+    row.
+    """
+    compiler_module = "django.db.models.sql.compiler"
+
+    # Integer field safe ranges by `internal_type` as documented
+    # in docs/ref/models/fields.txt.
+    integer_field_ranges = {
+        'SmallIntegerField': (-32768, 32767),
+        'IntegerField': (-2147483648, 2147483647),
+        'BigIntegerField': (-9223372036854775808, 9223372036854775807),
+        'PositiveSmallIntegerField': (0, 32767),
+        'PositiveIntegerField': (0, 2147483647),
+    }
+
+    def __init__(self, connection):
+        self.connection = connection
+        self._cache = None
+
+    def autoinc_sql(self, table, column):
+        """
+        Returns any SQL needed to support auto-incrementing primary keys, or
+        None if no SQL is necessary.
+
+        This SQL is executed when a table is created.
+        """
+        return None
+
+    def bulk_batch_size(self, fields, objs):
+        """
+        Returns the maximum allowed batch size for the backend. The fields
+        are the fields going to be inserted in the batch, the objs contains
+        all the objects to be inserted.
+        """
+        return len(objs)
+
+    def cache_key_culling_sql(self):
+        """
+        Returns an SQL query that retrieves the first cache key greater than the
+        n smallest.
+
+        This is used by the 'db' cache backend to determine where to start
+        culling.
+        """
+        return "SELECT cache_key FROM %s ORDER BY cache_key LIMIT 1 OFFSET %%s"
+
+    def unification_cast_sql(self, output_field):
+        """
+        Given a field instance, returns the SQL necessary to cast the result of
+        a union to that type. Note that the resulting string should contain a
+        '%s' placeholder for the expression being cast.
+        """
+        return '%s'
+
+    def date_extract_sql(self, lookup_type, field_name):
+        """
+        Given a lookup_type of 'year', 'month' or 'day', returns the SQL that
+        extracts a value from the given date field field_name.
+        """
+        raise NotImplementedError('subclasses of BaseDatabaseOperations may require a date_extract_sql() method')
+
+    def date_interval_sql(self, sql, connector, timedelta):
+        """
+        Implements the date interval functionality for expressions
+        """
+        raise NotImplementedError('subclasses of BaseDatabaseOperations may require a date_interval_sql() method')
+
+    def date_trunc_sql(self, lookup_type, field_name):
+        """
+        Given a lookup_type of 'year', 'month' or 'day', returns the SQL that
+        truncates the given date field field_name to a date object with only
+        the given specificity.
+        """
+        raise NotImplementedError('subclasses of BaseDatabaseOperations may require a datetrunc_sql() method')
+
+    def datetime_cast_sql(self):
+        """
+        Returns the SQL necessary to cast a datetime value so that it will be
+        retrieved as a Python datetime object instead of a string.
+
+        This SQL should include a '%s' in place of the field's name.
+        """
+        return "%s"
+
+    def datetime_extract_sql(self, lookup_type, field_name, tzname):
+        """
+        Given a lookup_type of 'year', 'month', 'day', 'hour', 'minute' or
+        'second', returns the SQL that extracts a value from the given
+        datetime field field_name, and a tuple of parameters.
+        """
+        raise NotImplementedError('subclasses of BaseDatabaseOperations may require a datetime_extract_sql() method')
+
+    def datetime_trunc_sql(self, lookup_type, field_name, tzname):
+        """
+        Given a lookup_type of 'year', 'month', 'day', 'hour', 'minute' or
+        'second', returns the SQL that truncates the given datetime field
+        field_name to a datetime object with only the given specificity, and
+        a tuple of parameters.
+        """
+        raise NotImplementedError('subclasses of BaseDatabaseOperations may require a datetime_trunk_sql() method')
+
+    def deferrable_sql(self):
+        """
+        Returns the SQL necessary to make a constraint "initially deferred"
+        during a CREATE TABLE statement.
+        """
+        return ''
+
+    def distinct_sql(self, fields):
+        """
+        Returns an SQL DISTINCT clause which removes duplicate rows from the
+        result set. If any fields are given, only the given fields are being
+        checked for duplicates.
+        """
+        if fields:
+            raise NotImplementedError('DISTINCT ON fields is not supported by this database backend')
+        else:
+            return 'DISTINCT'
+
+    def drop_foreignkey_sql(self):
+        """
+        Returns the SQL command that drops a foreign key.
+        """
+        return "DROP CONSTRAINT"
+
+    def drop_sequence_sql(self, table):
+        """
+        Returns any SQL necessary to drop the sequence for the given table.
+        Returns None if no SQL is necessary.
+        """
+        return None
+
+    def fetch_returned_insert_id(self, cursor):
+        """
+        Given a cursor object that has just performed an INSERT...RETURNING
+        statement into a table that has an auto-incrementing ID, returns the
+        newly created ID.
+        """
+        return cursor.fetchone()[0]
+
+    def field_cast_sql(self, db_type, internal_type):
+        """
+        Given a column type (e.g. 'BLOB', 'VARCHAR'), and an internal type
+        (e.g. 'GenericIPAddressField'), returns the SQL necessary to cast it
+        before using it in a WHERE statement. Note that the resulting string
+        should contain a '%s' placeholder for the column being searched against.
+        """
+        return '%s'
+
+    def force_no_ordering(self):
+        """
+        Returns a list used in the "ORDER BY" clause to force no ordering at
+        all. Returning an empty list means that nothing will be included in the
+        ordering.
+        """
+        return []
+
+    def for_update_sql(self, nowait=False):
+        """
+        Returns the FOR UPDATE SQL clause to lock rows for an update operation.
+        """
+        if nowait:
+            return 'FOR UPDATE NOWAIT'
+        else:
+            return 'FOR UPDATE'
+
+    def fulltext_search_sql(self, field_name):
+        """
+        Returns the SQL WHERE clause to use in order to perform a full-text
+        search of the given field_name. Note that the resulting string should
+        contain a '%s' placeholder for the value being searched against.
+        """
+        raise NotImplementedError('Full-text search is not implemented for this database backend')
+
+    def last_executed_query(self, cursor, sql, params):
+        """
+        Returns a string of the query last executed by the given cursor, with
+        placeholders replaced with actual values.
+
+        `sql` is the raw query containing placeholders, and `params` is the
+        sequence of parameters. These are used by default, but this method
+        exists for database backends to provide a better implementation
+        according to their own quoting schemes.
+        """
+        # Convert params to contain Unicode values.
+        to_unicode = lambda s: force_text(s, strings_only=True, errors='replace')
+        if isinstance(params, (list, tuple)):
+            u_params = tuple(to_unicode(val) for val in params)
+        elif params is None:
+            u_params = ()
+        else:
+            u_params = {to_unicode(k): to_unicode(v) for k, v in params.items()}
+
+        return six.text_type("QUERY = %r - PARAMS = %r") % (sql, u_params)
+
+    def last_insert_id(self, cursor, table_name, pk_name):
+        """
+        Given a cursor object that has just performed an INSERT statement into
+        a table that has an auto-incrementing ID, returns the newly created ID.
+
+        This method also receives the table name and the name of the primary-key
+        column.
+        """
+        return cursor.lastrowid
+
+    def lookup_cast(self, lookup_type):
+        """
+        Returns the string to use in a query when performing lookups
+        ("contains", "like", etc). The resulting string should contain a '%s'
+        placeholder for the column being searched against.
+        """
+        return "%s"
+
+    def max_in_list_size(self):
+        """
+        Returns the maximum number of items that can be passed in a single 'IN'
+        list condition, or None if the backend does not impose a limit.
+        """
+        return None
+
+    def max_name_length(self):
+        """
+        Returns the maximum length of table and column names, or None if there
+        is no limit.
+        """
+        return None
+
+    def no_limit_value(self):
+        """
+        Returns the value to use for the LIMIT when we are wanting "LIMIT
+        infinity". Returns None if the limit clause can be omitted in this case.
+        """
+        raise NotImplementedError('subclasses of BaseDatabaseOperations may require a no_limit_value() method')
+
+    def pk_default_value(self):
+        """
+        Returns the value to use during an INSERT statement to specify that
+        the field should use its default value.
+        """
+        return 'DEFAULT'
+
+    def prepare_sql_script(self, sql, _allow_fallback=False):
+        """
+        Takes a SQL script that may contain multiple lines and returns a list
+        of statements to feed to successive cursor.execute() calls.
+
+        Since few databases are able to process raw SQL scripts in a single
+        cursor.execute() call and PEP 249 doesn't talk about this use case,
+        the default implementation is conservative.
+        """
+        # Remove _allow_fallback and keep only 'return ...' in Django 1.9.
+        try:
+            # This import must stay inside the method because it's optional.
+            import sqlparse
+        except ImportError:
+            if _allow_fallback:
+                # Without sqlparse, fall back to the legacy (and buggy) logic.
+                warnings.warn(
+                    "Providing initial SQL data on a %s database will require "
+                    "sqlparse in Django 1.9." % self.connection.vendor,
+                    RemovedInDjango19Warning)
+                from django.core.management.sql import _split_statements
+                return _split_statements(sql)
+            else:
+                raise
+        else:
+            return [sqlparse.format(statement, strip_comments=True)
+                    for statement in sqlparse.split(sql) if statement]
+
+    def process_clob(self, value):
+        """
+        Returns the value of a CLOB column, for backends that return a locator
+        object that requires additional processing.
+        """
+        return value
+
+    def return_insert_id(self):
+        """
+        For backends that support returning the last insert ID as part
+        of an insert query, this method returns the SQL and params to
+        append to the INSERT query. The returned fragment should
+        contain a format string to hold the appropriate column.
+        """
+        pass
+
+    def compiler(self, compiler_name):
+        """
+        Returns the SQLCompiler class corresponding to the given name,
+        in the namespace corresponding to the `compiler_module` attribute
+        on this backend.
+        """
+        if self._cache is None:
+            self._cache = import_module(self.compiler_module)
+        return getattr(self._cache, compiler_name)
+
+    def quote_name(self, name):
+        """
+        Returns a quoted version of the given table, index or column name. Does
+        not quote the given name if it's already been quoted.
+        """
+        raise NotImplementedError('subclasses of BaseDatabaseOperations may require a quote_name() method')
+
+    def random_function_sql(self):
+        """
+        Returns an SQL expression that returns a random value.
+        """
+        return 'RANDOM()'
+
+    def regex_lookup(self, lookup_type):
+        """
+        Returns the string to use in a query when performing regular expression
+        lookups (using "regex" or "iregex"). The resulting string should
+        contain a '%s' placeholder for the column being searched against.
+
+        If the feature is not supported (or part of it is not supported), a
+        NotImplementedError exception can be raised.
+        """
+        raise NotImplementedError('subclasses of BaseDatabaseOperations may require a regex_lookup() method')
+
+    def savepoint_create_sql(self, sid):
+        """
+        Returns the SQL for starting a new savepoint. Only required if the
+        "uses_savepoints" feature is True. The "sid" parameter is a string
+        for the savepoint id.
+        """
+        return "SAVEPOINT %s" % self.quote_name(sid)
+
+    def savepoint_commit_sql(self, sid):
+        """
+        Returns the SQL for committing the given savepoint.
+        """
+        return "RELEASE SAVEPOINT %s" % self.quote_name(sid)
+
+    def savepoint_rollback_sql(self, sid):
+        """
+        Returns the SQL for rolling back the given savepoint.
+        """
+        return "ROLLBACK TO SAVEPOINT %s" % self.quote_name(sid)
+
+    def set_time_zone_sql(self):
+        """
+        Returns the SQL that will set the connection's time zone.
+
+        Returns '' if the backend doesn't support time zones.
+        """
+        return ''
+
+    def sql_flush(self, style, tables, sequences, allow_cascade=False):
+        """
+        Returns a list of SQL statements required to remove all data from
+        the given database tables (without actually removing the tables
+        themselves).
+
+        The returned value also includes SQL statements required to reset DB
+        sequences passed in :param sequences:.
+
+        The `style` argument is a Style object as returned by either
+        color_style() or no_style() in django.core.management.color.
+
+        The `allow_cascade` argument determines whether truncation may cascade
+        to tables with foreign keys pointing the tables being truncated.
+        PostgreSQL requires a cascade even if these tables are empty.
+        """
+        raise NotImplementedError('subclasses of BaseDatabaseOperations must provide a sql_flush() method')
+
+    def sequence_reset_by_name_sql(self, style, sequences):
+        """
+        Returns a list of the SQL statements required to reset sequences
+        passed in :param sequences:.
+
+        The `style` argument is a Style object as returned by either
+        color_style() or no_style() in django.core.management.color.
+        """
+        return []
+
+    def sequence_reset_sql(self, style, model_list):
+        """
+        Returns a list of the SQL statements required to reset sequences for
+        the given models.
+
+        The `style` argument is a Style object as returned by either
+        color_style() or no_style() in django.core.management.color.
+        """
+        return []  # No sequence reset required by default.
+
+    def start_transaction_sql(self):
+        """
+        Returns the SQL statement required to start a transaction.
+        """
+        return "BEGIN;"
+
+    def end_transaction_sql(self, success=True):
+        """
+        Returns the SQL statement required to end a transaction.
+        """
+        if not success:
+            return "ROLLBACK;"
+        return "COMMIT;"
+
+    def tablespace_sql(self, tablespace, inline=False):
+        """
+        Returns the SQL that will be used in a query to define the tablespace.
+
+        Returns '' if the backend doesn't support tablespaces.
+
+        If inline is True, the SQL is appended to a row; otherwise it's appended
+        to the entire CREATE TABLE or CREATE INDEX statement.
+        """
+        return ''
+
+    def prep_for_like_query(self, x):
+        """Prepares a value for use in a LIKE query."""
+        return force_text(x).replace("\\", "\\\\").replace("%", "\%").replace("_", "\_")
+
+    # Same as prep_for_like_query(), but called for "iexact" matches, which
+    # need not necessarily be implemented using "LIKE" in the backend.
+    prep_for_iexact_query = prep_for_like_query
+
+    def validate_autopk_value(self, value):
+        """
+        Certain backends do not accept some values for "serial" fields
+        (for example zero in MySQL). This method will raise a ValueError
+        if the value is invalid, otherwise returns validated value.
+        """
+        return value
+
+    def value_to_db_date(self, value):
+        """
+        Transform a date value to an object compatible with what is expected
+        by the backend driver for date columns.
+        """
+        if value is None:
+            return None
+        return six.text_type(value)
+
+    def value_to_db_datetime(self, value):
+        """
+        Transform a datetime value to an object compatible with what is expected
+        by the backend driver for datetime columns.
+        """
+        if value is None:
+            return None
+        return six.text_type(value)
+
+    def value_to_db_time(self, value):
+        """
+        Transform a time value to an object compatible with what is expected
+        by the backend driver for time columns.
+        """
+        if value is None:
+            return None
+        if timezone.is_aware(value):
+            raise ValueError("Django does not support timezone-aware times.")
+        return six.text_type(value)
+
+    def value_to_db_decimal(self, value, max_digits, decimal_places):
+        """
+        Transform a decimal.Decimal value to an object compatible with what is
+        expected by the backend driver for decimal (numeric) columns.
+        """
+        return utils.format_number(value, max_digits, decimal_places)
+
+    def year_lookup_bounds_for_date_field(self, value):
+        """
+        Returns a two-elements list with the lower and upper bound to be used
+        with a BETWEEN operator to query a DateField value using a year
+        lookup.
+
+        `value` is an int, containing the looked-up year.
+        """
+        first = datetime.date(value, 1, 1)
+        second = datetime.date(value, 12, 31)
+        return [first, second]
+
+    def year_lookup_bounds_for_datetime_field(self, value):
+        """
+        Returns a two-elements list with the lower and upper bound to be used
+        with a BETWEEN operator to query a DateTimeField value using a year
+        lookup.
+
+        `value` is an int, containing the looked-up year.
+        """
+        first = datetime.datetime(value, 1, 1)
+        second = datetime.datetime(value, 12, 31, 23, 59, 59, 999999)
+        if settings.USE_TZ:
+            tz = timezone.get_current_timezone()
+            first = timezone.make_aware(first, tz)
+            second = timezone.make_aware(second, tz)
+        return [first, second]
+
+    def get_db_converters(self, expression):
+        """Get a list of functions needed to convert field data.
+
+        Some field types on some backends do not provide data in the correct
+        format, this is the hook for coverter functions.
+        """
+        return []
+
+    def convert_durationfield_value(self, value, expression, context):
+        if value is not None:
+            value = str(decimal.Decimal(value) / decimal.Decimal(1000000))
+            value = parse_duration(value)
+        return value
+
+    def check_aggregate_support(self, aggregate_func):
+        """Check that the backend supports the provided aggregate
+
+        This is used on specific backends to rule out known aggregates
+        that are known to have faulty implementations. If the named
+        aggregate function has a known problem, the backend should
+        raise NotImplementedError.
+        """
+        pass
+
+    def combine_expression(self, connector, sub_expressions):
+        """Combine a list of subexpressions into a single expression, using
+        the provided connecting operator. This is required because operators
+        can vary between backends (e.g., Oracle with %% and &) and between
+        subexpression types (e.g., date expressions)
+        """
+        conn = ' %s ' % connector
+        return conn.join(sub_expressions)
+
+    def combine_duration_expression(self, connector, sub_expressions):
+        return self.combine_expression(connector, sub_expressions)
+
+    def modify_insert_params(self, placeholders, params):
+        """Allow modification of insert parameters. Needed for Oracle Spatial
+        backend due to #10888.
+        """
+        return params
+
+    def integer_field_range(self, internal_type):
+        """
+        Given an integer field internal type (e.g. 'PositiveIntegerField'),
+        returns a tuple of the (min_value, max_value) form representing the
+        range of the column type bound to the field.
+        """
+        return self.integer_field_ranges[internal_type]

django/db/backends/schema.py → django/db/backends/base/schema.py

@@ -3,9 +3,9 @@ import hashlib
 from django.db.backends.utils import truncate_name
 from django.db.models.fields.related import ManyToManyField
 from django.db.transaction import atomic
+from django.utils import six
 from django.utils.encoding import force_bytes
 from django.utils.log import getLogger
-from django.utils import six
 
 logger = getLogger('django.db.backends.schema')
 

django/db/backends/base/validation.py

@@ -0,0 +1,38 @@
+from django.core import checks
+
+
+class BaseDatabaseValidation(object):
+    """
+    This class encapsulates all backend-specific model validation.
+    """
+    def __init__(self, connection):
+        self.connection = connection
+
+    def validate_field(self, errors, opts, f):
+        """
+        By default, there is no backend-specific validation.
+
+        This method has been deprecated by the new checks framework. New
+        backends should implement check_field instead.
+        """
+        # This is deliberately commented out. It exists as a marker to
+        # remind us to remove this method, and the check_field() shim,
+        # when the time comes.
+        # warnings.warn('"validate_field" has been deprecated", RemovedInDjango19Warning)
+        pass
+
+    def check_field(self, field, **kwargs):
+        class ErrorList(list):
+            """A dummy list class that emulates API used by the older
+            validate_field() method. When validate_field() is fully
+            deprecated, this dummy can be removed too.
+            """
+            def add(self, opts, error_message):
+                self.append(checks.Error(error_message, hint=None, obj=field))
+
+        errors = ErrorList()
+        # Some tests create fields in isolation -- the fields are not attached
+        # to any model, so they have no `model` attribute.
+        opts = field.model._meta if hasattr(field, 'model') else None
+        self.validate_field(errors, field, opts)
+        return list(errors)

django/db/backends/dummy/base.py

@@ -8,10 +8,13 @@ ImproperlyConfigured.
 """
 
 from django.core.exceptions import ImproperlyConfigured
-from django.db.backends import (BaseDatabaseOperations, BaseDatabaseClient,
-    BaseDatabaseIntrospection, BaseDatabaseWrapper, BaseDatabaseFeatures,
-    BaseDatabaseValidation)
-from django.db.backends.creation import BaseDatabaseCreation
+from django.db.backends.base.base import BaseDatabaseWrapper
+from django.db.backends.base.client import BaseDatabaseClient
+from django.db.backends.base.creation import BaseDatabaseCreation
+from django.db.backends.base.features import BaseDatabaseFeatures
+from django.db.backends.base.operations import BaseDatabaseOperations
+from django.db.backends.base.introspection import BaseDatabaseIntrospection
+from django.db.backends.base.validation import BaseDatabaseValidation
 
 
 def complain(*args, **kwargs):

django/db/backends/mysql/base.py

@@ -9,15 +9,35 @@ from __future__ import unicode_literals
 import datetime
 import re
 import sys
-import uuid
 import warnings
 
+from django.conf import settings
+from django.db import utils
+from django.db.backends import utils as backend_utils
+from django.db.backends.base.base import BaseDatabaseWrapper
+from django.utils.encoding import force_str
+from django.db.backends.mysql.schema import DatabaseSchemaEditor
+from django.utils import six, timezone
+from django.utils.functional import cached_property
+from django.utils.safestring import SafeBytes, SafeText
+
 try:
     import MySQLdb as Database
 except ImportError as e:
     from django.core.exceptions import ImproperlyConfigured
     raise ImproperlyConfigured("Error loading MySQLdb module: %s" % e)
 
+from MySQLdb.converters import conversions, Thing2Literal
+from MySQLdb.constants import FIELD_TYPE, CLIENT
+
+# Some of these import MySQLdb, so import them after checking if it's installed.
+from .client import DatabaseClient
+from .creation import DatabaseCreation
+from .features import DatabaseFeatures
+from .introspection import DatabaseIntrospection
+from .operations import DatabaseOperations
+from .validation import DatabaseValidation
+
 # We want version (1, 2, 1, 'final', 2) or later. We can't just use
 # lexicographic ordering in this check because then (1, 2, 1, 'gamma')
 # inadvertently passes the version test.
@@ -27,28 +47,6 @@ if (version < (1, 2, 1) or (version[:3] == (1, 2, 1) and
     from django.core.exceptions import ImproperlyConfigured
     raise ImproperlyConfigured("MySQLdb-1.2.1p2 or newer is required; you have %s" % Database.__version__)
 
-from MySQLdb.converters import conversions, Thing2Literal
-from MySQLdb.constants import FIELD_TYPE, CLIENT
-
-try:
-    import pytz
-except ImportError:
-    pytz = None
-
-from django.conf import settings
-from django.db import utils
-from django.db.backends import (utils as backend_utils, BaseDatabaseFeatures,
-    BaseDatabaseOperations, BaseDatabaseWrapper)
-from django.db.backends.mysql.client import DatabaseClient
-from django.db.backends.mysql.creation import DatabaseCreation
-from django.db.backends.mysql.introspection import DatabaseIntrospection
-from django.db.backends.mysql.validation import DatabaseValidation
-from django.utils.encoding import force_str, force_text
-from django.db.backends.mysql.schema import DatabaseSchemaEditor
-from django.utils.functional import cached_property
-from django.utils.safestring import SafeBytes, SafeText
-from django.utils import six
-from django.utils import timezone
 
 DatabaseError = Database.DatabaseError
 IntegrityError = Database.IntegrityError
@@ -159,259 +157,6 @@ class CursorWrapper(object):
         self.close()
 
 
-class DatabaseFeatures(BaseDatabaseFeatures):
-    empty_fetchmany_value = ()
-    update_can_self_select = False
-    allows_group_by_pk = True
-    related_fields_match_type = True
-    allow_sliced_subqueries = False
-    has_bulk_insert = True
-    has_select_for_update = True
-    has_select_for_update_nowait = False
-    supports_forward_references = False
-    supports_regex_backreferencing = False
-    supports_date_lookup_using_string = False
-    can_introspect_autofield = True
-    can_introspect_binary_field = False
-    can_introspect_small_integer_field = True
-    supports_timezones = False
-    requires_explicit_null_ordering_when_grouping = True
-    allows_auto_pk_0 = False
-    uses_savepoints = True
-    can_release_savepoints = True
-    atomic_transactions = False
-    supports_column_check_constraints = False
-
-    @cached_property
-    def _mysql_storage_engine(self):
-        "Internal method used in Django tests. Don't rely on this from your code"
-        with self.connection.cursor() as cursor:
-            cursor.execute("SELECT ENGINE FROM INFORMATION_SCHEMA.ENGINES WHERE SUPPORT = 'DEFAULT'")
-            result = cursor.fetchone()
-        return result[0]
-
-    @cached_property
-    def can_introspect_foreign_keys(self):
-        "Confirm support for introspected foreign keys"
-        return self._mysql_storage_engine != 'MyISAM'
-
-    @cached_property
-    def supports_microsecond_precision(self):
-        # See https://github.com/farcepest/MySQLdb1/issues/24 for the reason
-        # about requiring MySQLdb 1.2.5
-        return self.connection.mysql_version >= (5, 6, 4) and Database.version_info >= (1, 2, 5)
-
-    @cached_property
-    def has_zoneinfo_database(self):
-        # MySQL accepts full time zones names (eg. Africa/Nairobi) but rejects
-        # abbreviations (eg. EAT). When pytz isn't installed and the current
-        # time zone is LocalTimezone (the only sensible value in this
-        # context), the current time zone name will be an abbreviation. As a
-        # consequence, MySQL cannot perform time zone conversions reliably.
-        if pytz is None:
-            return False
-
-        # Test if the time zone definitions are installed.
-        with self.connection.cursor() as cursor:
-            cursor.execute("SELECT 1 FROM mysql.time_zone LIMIT 1")
-            return cursor.fetchone() is not None
-
-    def introspected_boolean_field_type(self, *args, **kwargs):
-        return 'IntegerField'
-
-
-class DatabaseOperations(BaseDatabaseOperations):
-    compiler_module = "django.db.backends.mysql.compiler"
-
-    # MySQL stores positive fields as UNSIGNED ints.
-    integer_field_ranges = dict(BaseDatabaseOperations.integer_field_ranges,
-        PositiveSmallIntegerField=(0, 4294967295),
-        PositiveIntegerField=(0, 18446744073709551615),
-    )
-
-    def date_extract_sql(self, lookup_type, field_name):
-        # http://dev.mysql.com/doc/mysql/en/date-and-time-functions.html
-        if lookup_type == 'week_day':
-            # DAYOFWEEK() returns an integer, 1-7, Sunday=1.
-            # Note: WEEKDAY() returns 0-6, Monday=0.
-            return "DAYOFWEEK(%s)" % field_name
-        else:
-            return "EXTRACT(%s FROM %s)" % (lookup_type.upper(), field_name)
-
-    def date_trunc_sql(self, lookup_type, field_name):
-        fields = ['year', 'month', 'day', 'hour', 'minute', 'second']
-        format = ('%%Y-', '%%m', '-%%d', ' %%H:', '%%i', ':%%s')  # Use double percents to escape.
-        format_def = ('0000-', '01', '-01', ' 00:', '00', ':00')
-        try:
-            i = fields.index(lookup_type) + 1
-        except ValueError:
-            sql = field_name
-        else:
-            format_str = ''.join([f for f in format[:i]] + [f for f in format_def[i:]])
-            sql = "CAST(DATE_FORMAT(%s, '%s') AS DATETIME)" % (field_name, format_str)
-        return sql
-
-    def datetime_extract_sql(self, lookup_type, field_name, tzname):
-        if settings.USE_TZ:
-            field_name = "CONVERT_TZ(%s, 'UTC', %%s)" % field_name
-            params = [tzname]
-        else:
-            params = []
-        # http://dev.mysql.com/doc/mysql/en/date-and-time-functions.html
-        if lookup_type == 'week_day':
-            # DAYOFWEEK() returns an integer, 1-7, Sunday=1.
-            # Note: WEEKDAY() returns 0-6, Monday=0.
-            sql = "DAYOFWEEK(%s)" % field_name
-        else:
-            sql = "EXTRACT(%s FROM %s)" % (lookup_type.upper(), field_name)
-        return sql, params
-
-    def datetime_trunc_sql(self, lookup_type, field_name, tzname):
-        if settings.USE_TZ:
-            field_name = "CONVERT_TZ(%s, 'UTC', %%s)" % field_name
-            params = [tzname]
-        else:
-            params = []
-        fields = ['year', 'month', 'day', 'hour', 'minute', 'second']
-        format = ('%%Y-', '%%m', '-%%d', ' %%H:', '%%i', ':%%s')  # Use double percents to escape.
-        format_def = ('0000-', '01', '-01', ' 00:', '00', ':00')
-        try:
-            i = fields.index(lookup_type) + 1
-        except ValueError:
-            sql = field_name
-        else:
-            format_str = ''.join([f for f in format[:i]] + [f for f in format_def[i:]])
-            sql = "CAST(DATE_FORMAT(%s, '%s') AS DATETIME)" % (field_name, format_str)
-        return sql, params
-
-    def date_interval_sql(self, timedelta):
-        return "INTERVAL '%d 0:0:%d:%d' DAY_MICROSECOND" % (
-            timedelta.days, timedelta.seconds, timedelta.microseconds), []
-
-    def format_for_duration_arithmetic(self, sql):
-        return 'INTERVAL %s MICROSECOND' % sql
-
-    def drop_foreignkey_sql(self):
-        return "DROP FOREIGN KEY"
-
-    def force_no_ordering(self):
-        """
-        "ORDER BY NULL" prevents MySQL from implicitly ordering by grouped
-        columns. If no ordering would otherwise be applied, we don't want any
-        implicit sorting going on.
-        """
-        return [(None, ("NULL", [], False))]
-
-    def fulltext_search_sql(self, field_name):
-        return 'MATCH (%s) AGAINST (%%s IN BOOLEAN MODE)' % field_name
-
-    def last_executed_query(self, cursor, sql, params):
-        # With MySQLdb, cursor objects have an (undocumented) "_last_executed"
-        # attribute where the exact query sent to the database is saved.
-        # See MySQLdb/cursors.py in the source distribution.
-        return force_text(getattr(cursor, '_last_executed', None), errors='replace')
-
-    def no_limit_value(self):
-        # 2**64 - 1, as recommended by the MySQL documentation
-        return 18446744073709551615
-
-    def quote_name(self, name):
-        if name.startswith("`") and name.endswith("`"):
-            return name  # Quoting once is enough.
-        return "`%s`" % name
-
-    def random_function_sql(self):
-        return 'RAND()'
-
-    def sql_flush(self, style, tables, sequences, allow_cascade=False):
-        # NB: The generated SQL below is specific to MySQL
-        # 'TRUNCATE x;', 'TRUNCATE y;', 'TRUNCATE z;'... style SQL statements
-        # to clear all tables of all data
-        if tables:
-            sql = ['SET FOREIGN_KEY_CHECKS = 0;']
-            for table in tables:
-                sql.append('%s %s;' % (
-                    style.SQL_KEYWORD('TRUNCATE'),
-                    style.SQL_FIELD(self.quote_name(table)),
-                ))
-            sql.append('SET FOREIGN_KEY_CHECKS = 1;')
-            sql.extend(self.sequence_reset_by_name_sql(style, sequences))
-            return sql
-        else:
-            return []
-
-    def validate_autopk_value(self, value):
-        # MySQLism: zero in AUTO_INCREMENT field does not work. Refs #17653.
-        if value == 0:
-            raise ValueError('The database backend does not accept 0 as a '
-                             'value for AutoField.')
-        return value
-
-    def value_to_db_datetime(self, value):
-        if value is None:
-            return None
-
-        # MySQL doesn't support tz-aware datetimes
-        if timezone.is_aware(value):
-            if settings.USE_TZ:
-                value = value.astimezone(timezone.utc).replace(tzinfo=None)
-            else:
-                raise ValueError("MySQL backend does not support timezone-aware datetimes when USE_TZ is False.")
-
-        return six.text_type(value)
-
-    def value_to_db_time(self, value):
-        if value is None:
-            return None
-
-        # MySQL doesn't support tz-aware times
-        if timezone.is_aware(value):
-            raise ValueError("MySQL backend does not support timezone-aware times.")
-
-        return six.text_type(value)
-
-    def max_name_length(self):
-        return 64
-
-    def bulk_insert_sql(self, fields, num_values):
-        items_sql = "(%s)" % ", ".join(["%s"] * len(fields))
-        return "VALUES " + ", ".join([items_sql] * num_values)
-
-    def combine_expression(self, connector, sub_expressions):
-        """
-        MySQL requires special cases for ^ operators in query expressions
-        """
-        if connector == '^':
-            return 'POW(%s)' % ','.join(sub_expressions)
-        return super(DatabaseOperations, self).combine_expression(connector, sub_expressions)
-
-    def get_db_converters(self, expression):
-        converters = super(DatabaseOperations, self).get_db_converters(expression)
-        internal_type = expression.output_field.get_internal_type()
-        if internal_type in ['BooleanField', 'NullBooleanField']:
-            converters.append(self.convert_booleanfield_value)
-        if internal_type == 'UUIDField':
-            converters.append(self.convert_uuidfield_value)
-        if internal_type == 'TextField':
-            converters.append(self.convert_textfield_value)
-        return converters
-
-    def convert_booleanfield_value(self, value, expression, context):
-        if value in (0, 1):
-            value = bool(value)
-        return value
-
-    def convert_uuidfield_value(self, value, expression, context):
-        if value is not None:
-            value = uuid.UUID(value)
-        return value
-
-    def convert_textfield_value(self, value, expression, context):
-        if value is not None:
-            value = force_text(value)
-        return value
-
-
 class DatabaseWrapper(BaseDatabaseWrapper):
     vendor = 'mysql'
     # This dictionary maps Field objects to their associated MySQL column

django/db/backends/mysql/client.py

@@ -1,6 +1,6 @@
 import subprocess
 
-from django.db.backends import BaseDatabaseClient
+from django.db.backends.base.client import BaseDatabaseClient
 
 
 class DatabaseClient(BaseDatabaseClient):

django/db/backends/mysql/creation.py

@@ -1,4 +1,4 @@
-from django.db.backends.creation import BaseDatabaseCreation
+from django.db.backends.base.creation import BaseDatabaseCreation
 
 
 class DatabaseCreation(BaseDatabaseCreation):

django/db/backends/mysql/features.py

@@ -0,0 +1,70 @@
+from django.db.backends.base.features import BaseDatabaseFeatures
+from django.utils.functional import cached_property
+
+from .base import Database
+
+try:
+    import pytz
+except ImportError:
+    pytz = None
+
+
+class DatabaseFeatures(BaseDatabaseFeatures):
+    empty_fetchmany_value = ()
+    update_can_self_select = False
+    allows_group_by_pk = True
+    related_fields_match_type = True
+    allow_sliced_subqueries = False
+    has_bulk_insert = True
+    has_select_for_update = True
+    has_select_for_update_nowait = False
+    supports_forward_references = False
+    supports_regex_backreferencing = False
+    supports_date_lookup_using_string = False
+    can_introspect_autofield = True
+    can_introspect_binary_field = False
+    can_introspect_small_integer_field = True
+    supports_timezones = False
+    requires_explicit_null_ordering_when_grouping = True
+    allows_auto_pk_0 = False
+    uses_savepoints = True
+    can_release_savepoints = True
+    atomic_transactions = False
+    supports_column_check_constraints = False
+
+    @cached_property
+    def _mysql_storage_engine(self):
+        "Internal method used in Django tests. Don't rely on this from your code"
+        with self.connection.cursor() as cursor:
+            cursor.execute("SELECT ENGINE FROM INFORMATION_SCHEMA.ENGINES WHERE SUPPORT = 'DEFAULT'")
+            result = cursor.fetchone()
+        return result[0]
+
+    @cached_property
+    def can_introspect_foreign_keys(self):
+        "Confirm support for introspected foreign keys"
+        return self._mysql_storage_engine != 'MyISAM'
+
+    @cached_property
+    def supports_microsecond_precision(self):
+        # See https://github.com/farcepest/MySQLdb1/issues/24 for the reason
+        # about requiring MySQLdb 1.2.5
+        return self.connection.mysql_version >= (5, 6, 4) and Database.version_info >= (1, 2, 5)
+
+    @cached_property
+    def has_zoneinfo_database(self):
+        # MySQL accepts full time zones names (eg. Africa/Nairobi) but rejects
+        # abbreviations (eg. EAT). When pytz isn't installed and the current
+        # time zone is LocalTimezone (the only sensible value in this
+        # context), the current time zone name will be an abbreviation. As a
+        # consequence, MySQL cannot perform time zone conversions reliably.
+        if pytz is None:
+            return False
+
+        # Test if the time zone definitions are installed.
+        with self.connection.cursor() as cursor:
+            cursor.execute("SELECT 1 FROM mysql.time_zone LIMIT 1")
+            return cursor.fetchone() is not None
+
+    def introspected_boolean_field_type(self, *args, **kwargs):
+        return 'IntegerField'

django/db/backends/mysql/introspection.py

@@ -1,10 +1,14 @@
 from collections import namedtuple
 import re
-from .base import FIELD_TYPE
+
 from django.utils.datastructures import OrderedSet
-from django.db.backends import BaseDatabaseIntrospection, FieldInfo, TableInfo
+from django.db.backends.base.introspection import (
+    BaseDatabaseIntrospection, FieldInfo, TableInfo,
+)
 from django.utils.encoding import force_text
 
+from MySQLdb.constants import FIELD_TYPE
+
 FieldInfo = namedtuple('FieldInfo', FieldInfo._fields + ('extra',))
 
 foreign_key_re = re.compile(r"\sCONSTRAINT `[^`]*` FOREIGN KEY \(`([^`]*)`\) REFERENCES `([^`]*)` \(`([^`]*)`\)")

django/db/backends/mysql/operations.py

@@ -0,0 +1,200 @@
+from __future__ import unicode_literals
+
+import uuid
+
+from django.conf import settings
+from django.db.backends.base.operations import BaseDatabaseOperations
+from django.utils import six, timezone
+from django.utils.encoding import force_text
+
+
+class DatabaseOperations(BaseDatabaseOperations):
+    compiler_module = "django.db.backends.mysql.compiler"
+
+    # MySQL stores positive fields as UNSIGNED ints.
+    integer_field_ranges = dict(BaseDatabaseOperations.integer_field_ranges,
+        PositiveSmallIntegerField=(0, 4294967295),
+        PositiveIntegerField=(0, 18446744073709551615),
+    )
+
+    def date_extract_sql(self, lookup_type, field_name):
+        # http://dev.mysql.com/doc/mysql/en/date-and-time-functions.html
+        if lookup_type == 'week_day':
+            # DAYOFWEEK() returns an integer, 1-7, Sunday=1.
+            # Note: WEEKDAY() returns 0-6, Monday=0.
+            return "DAYOFWEEK(%s)" % field_name
+        else:
+            return "EXTRACT(%s FROM %s)" % (lookup_type.upper(), field_name)
+
+    def date_trunc_sql(self, lookup_type, field_name):
+        fields = ['year', 'month', 'day', 'hour', 'minute', 'second']
+        format = ('%%Y-', '%%m', '-%%d', ' %%H:', '%%i', ':%%s')  # Use double percents to escape.
+        format_def = ('0000-', '01', '-01', ' 00:', '00', ':00')
+        try:
+            i = fields.index(lookup_type) + 1
+        except ValueError:
+            sql = field_name
+        else:
+            format_str = ''.join([f for f in format[:i]] + [f for f in format_def[i:]])
+            sql = "CAST(DATE_FORMAT(%s, '%s') AS DATETIME)" % (field_name, format_str)
+        return sql
+
+    def datetime_extract_sql(self, lookup_type, field_name, tzname):
+        if settings.USE_TZ:
+            field_name = "CONVERT_TZ(%s, 'UTC', %%s)" % field_name
+            params = [tzname]
+        else:
+            params = []
+        # http://dev.mysql.com/doc/mysql/en/date-and-time-functions.html
+        if lookup_type == 'week_day':
+            # DAYOFWEEK() returns an integer, 1-7, Sunday=1.
+            # Note: WEEKDAY() returns 0-6, Monday=0.
+            sql = "DAYOFWEEK(%s)" % field_name
+        else:
+            sql = "EXTRACT(%s FROM %s)" % (lookup_type.upper(), field_name)
+        return sql, params
+
+    def datetime_trunc_sql(self, lookup_type, field_name, tzname):
+        if settings.USE_TZ:
+            field_name = "CONVERT_TZ(%s, 'UTC', %%s)" % field_name
+            params = [tzname]
+        else:
+            params = []
+        fields = ['year', 'month', 'day', 'hour', 'minute', 'second']
+        format = ('%%Y-', '%%m', '-%%d', ' %%H:', '%%i', ':%%s')  # Use double percents to escape.
+        format_def = ('0000-', '01', '-01', ' 00:', '00', ':00')
+        try:
+            i = fields.index(lookup_type) + 1
+        except ValueError:
+            sql = field_name
+        else:
+            format_str = ''.join([f for f in format[:i]] + [f for f in format_def[i:]])
+            sql = "CAST(DATE_FORMAT(%s, '%s') AS DATETIME)" % (field_name, format_str)
+        return sql, params
+
+    def date_interval_sql(self, timedelta):
+        return "INTERVAL '%d 0:0:%d:%d' DAY_MICROSECOND" % (
+            timedelta.days, timedelta.seconds, timedelta.microseconds), []
+
+    def format_for_duration_arithmetic(self, sql):
+        return 'INTERVAL %s MICROSECOND' % sql
+
+    def drop_foreignkey_sql(self):
+        return "DROP FOREIGN KEY"
+
+    def force_no_ordering(self):
+        """
+        "ORDER BY NULL" prevents MySQL from implicitly ordering by grouped
+        columns. If no ordering would otherwise be applied, we don't want any
+        implicit sorting going on.
+        """
+        return [(None, ("NULL", [], False))]
+
+    def fulltext_search_sql(self, field_name):
+        return 'MATCH (%s) AGAINST (%%s IN BOOLEAN MODE)' % field_name
+
+    def last_executed_query(self, cursor, sql, params):
+        # With MySQLdb, cursor objects have an (undocumented) "_last_executed"
+        # attribute where the exact query sent to the database is saved.
+        # See MySQLdb/cursors.py in the source distribution.
+        return force_text(getattr(cursor, '_last_executed', None), errors='replace')
+
+    def no_limit_value(self):
+        # 2**64 - 1, as recommended by the MySQL documentation
+        return 18446744073709551615
+
+    def quote_name(self, name):
+        if name.startswith("`") and name.endswith("`"):
+            return name  # Quoting once is enough.
+        return "`%s`" % name
+
+    def random_function_sql(self):
+        return 'RAND()'
+
+    def sql_flush(self, style, tables, sequences, allow_cascade=False):
+        # NB: The generated SQL below is specific to MySQL
+        # 'TRUNCATE x;', 'TRUNCATE y;', 'TRUNCATE z;'... style SQL statements
+        # to clear all tables of all data
+        if tables:
+            sql = ['SET FOREIGN_KEY_CHECKS = 0;']
+            for table in tables:
+                sql.append('%s %s;' % (
+                    style.SQL_KEYWORD('TRUNCATE'),
+                    style.SQL_FIELD(self.quote_name(table)),
+                ))
+            sql.append('SET FOREIGN_KEY_CHECKS = 1;')
+            sql.extend(self.sequence_reset_by_name_sql(style, sequences))
+            return sql
+        else:
+            return []
+
+    def validate_autopk_value(self, value):
+        # MySQLism: zero in AUTO_INCREMENT field does not work. Refs #17653.
+        if value == 0:
+            raise ValueError('The database backend does not accept 0 as a '
+                             'value for AutoField.')
+        return value
+
+    def value_to_db_datetime(self, value):
+        if value is None:
+            return None
+
+        # MySQL doesn't support tz-aware datetimes
+        if timezone.is_aware(value):
+            if settings.USE_TZ:
+                value = value.astimezone(timezone.utc).replace(tzinfo=None)
+            else:
+                raise ValueError("MySQL backend does not support timezone-aware datetimes when USE_TZ is False.")
+
+        return six.text_type(value)
+
+    def value_to_db_time(self, value):
+        if value is None:
+            return None
+
+        # MySQL doesn't support tz-aware times
+        if timezone.is_aware(value):
+            raise ValueError("MySQL backend does not support timezone-aware times.")
+
+        return six.text_type(value)
+
+    def max_name_length(self):
+        return 64
+
+    def bulk_insert_sql(self, fields, num_values):
+        items_sql = "(%s)" % ", ".join(["%s"] * len(fields))
+        return "VALUES " + ", ".join([items_sql] * num_values)
+
+    def combine_expression(self, connector, sub_expressions):
+        """
+        MySQL requires special cases for ^ operators in query expressions
+        """
+        if connector == '^':
+            return 'POW(%s)' % ','.join(sub_expressions)
+        return super(DatabaseOperations, self).combine_expression(connector, sub_expressions)
+
+    def get_db_converters(self, expression):
+        converters = super(DatabaseOperations, self).get_db_converters(expression)
+        internal_type = expression.output_field.get_internal_type()
+        if internal_type in ['BooleanField', 'NullBooleanField']:
+            converters.append(self.convert_booleanfield_value)
+        if internal_type == 'UUIDField':
+            converters.append(self.convert_uuidfield_value)
+        if internal_type == 'TextField':
+            converters.append(self.convert_textfield_value)
+        return converters
+
+    def convert_booleanfield_value(self, value, expression, context):
+        if value in (0, 1):
+            value = bool(value)
+        return value
+
+    def convert_uuidfield_value(self, value, expression, context):
+        if value is not None:
+            value = uuid.UUID(value)
+        return value
+
+    def convert_textfield_value(self, value, expression, context):
+        if value is not None:
+            value = force_text(value)
+        return value

django/db/backends/mysql/schema.py

@@ -1,4 +1,4 @@
-from django.db.backends.schema import BaseDatabaseSchemaEditor
+from django.db.backends.base.schema import BaseDatabaseSchemaEditor
 from django.db.models import NOT_PROVIDED
 
 

django/db/backends/mysql/validation.py

@@ -1,5 +1,5 @@
 from django.core import checks
-from django.db.backends import BaseDatabaseValidation
+from django.db.backends.base.validation import BaseDatabaseValidation
 
 
 class DatabaseValidation(BaseDatabaseValidation):

django/db/backends/oracle/base.py

@@ -7,12 +7,20 @@ from __future__ import unicode_literals
 
 import datetime
 import decimal
-import re
+import os
 import platform
 import sys
-import uuid
 import warnings
 
+from django.conf import settings
+from django.db import utils
+from django.db.backends.base.base import BaseDatabaseWrapper
+from django.db.backends.base.validation import BaseDatabaseValidation
+from django.utils import six, timezone
+from django.utils.duration import duration_string
+from django.utils.encoding import force_bytes, force_text
+from django.utils.functional import cached_property
+
 
 def _setup_environment(environ):
     # Cygwin requires some special voodoo to set the environment variables
@@ -29,7 +37,6 @@ def _setup_environment(environ):
         for name, value in environ:
             kernel32.SetEnvironmentVariableA(name, value)
     else:
-        import os
         os.environ.update(environ)
 
 _setup_environment([
@@ -47,520 +54,18 @@ except ImportError as e:
     from django.core.exceptions import ImproperlyConfigured
     raise ImproperlyConfigured("Error loading cx_Oracle module: %s" % e)
 
-try:
-    import pytz
-except ImportError:
-    pytz = None
-
-from django.conf import settings
-from django.db import utils
-from django.db.backends import (BaseDatabaseFeatures, BaseDatabaseOperations,
-    BaseDatabaseWrapper, BaseDatabaseValidation, utils as backend_utils)
-from django.db.backends.oracle.client import DatabaseClient
-from django.db.backends.oracle.creation import DatabaseCreation
-from django.db.backends.oracle.introspection import DatabaseIntrospection
-from django.db.backends.oracle.schema import DatabaseSchemaEditor
-from django.db.utils import InterfaceError
-from django.utils import six, timezone
-from django.utils.duration import duration_string
-from django.utils.encoding import force_bytes, force_text
-from django.utils.functional import cached_property
-
+# Some of these import cx_Oracle, so import them after checking if it's installed.
+from .client import DatabaseClient
+from .creation import DatabaseCreation
+from .features import DatabaseFeatures
+from .introspection import DatabaseIntrospection
+from .operations import DatabaseOperations
+from .schema import DatabaseSchemaEditor
+from .utils import convert_unicode, Oracle_datetime
 
 DatabaseError = Database.DatabaseError
 IntegrityError = Database.IntegrityError
 
-# Check whether cx_Oracle was compiled with the WITH_UNICODE option if cx_Oracle is pre-5.1. This will
-# also be True for cx_Oracle 5.1 and in Python 3.0. See #19606
-if int(Database.version.split('.', 1)[0]) >= 5 and \
-        (int(Database.version.split('.', 2)[1]) >= 1 or
-         not hasattr(Database, 'UNICODE')):
-    convert_unicode = force_text
-else:
-    convert_unicode = force_bytes
-
-
-class Oracle_datetime(datetime.datetime):
-    """
-    A datetime object, with an additional class attribute
-    to tell cx_Oracle to save the microseconds too.
-    """
-    input_size = Database.TIMESTAMP
-
-    @classmethod
-    def from_datetime(cls, dt):
-        return Oracle_datetime(dt.year, dt.month, dt.day,
-                               dt.hour, dt.minute, dt.second, dt.microsecond)
-
-
-class DatabaseFeatures(BaseDatabaseFeatures):
-    empty_fetchmany_value = ()
-    needs_datetime_string_cast = False
-    interprets_empty_strings_as_nulls = True
-    uses_savepoints = True
-    has_select_for_update = True
-    has_select_for_update_nowait = True
-    can_return_id_from_insert = True
-    allow_sliced_subqueries = False
-    supports_subqueries_in_group_by = False
-    supports_transactions = True
-    supports_timezones = False
-    has_zoneinfo_database = pytz is not None
-    supports_bitwise_or = False
-    has_native_duration_field = True
-    can_defer_constraint_checks = True
-    supports_partially_nullable_unique_constraints = False
-    truncates_names = True
-    has_bulk_insert = True
-    supports_tablespaces = True
-    supports_sequence_reset = False
-    can_introspect_max_length = False
-    can_introspect_time_field = False
-    atomic_transactions = False
-    supports_combined_alters = False
-    nulls_order_largest = True
-    requires_literal_defaults = True
-    connection_persists_old_columns = True
-    closed_cursor_error_class = InterfaceError
-    bare_select_suffix = " FROM DUAL"
-    uppercases_column_names = True
-    # select for update with limit can be achieved on Oracle, but not with the current backend.
-    supports_select_for_update_with_limit = False
-
-    def introspected_boolean_field_type(self, field=None, created_separately=False):
-        """
-        Some versions of Oracle -- we've seen this on 11.2.0.1 and suspect
-        it goes back -- have a weird bug where, when an integer column is
-        added to an existing table with a default, its precision is later
-        reported on introspection as 0, regardless of the real precision.
-        For Django introspection, this means that such columns are reported
-        as IntegerField even if they are really BigIntegerField or BooleanField.
-
-        The bug is solved in Oracle 11.2.0.2 and up.
-        """
-        if self.connection.oracle_full_version < '11.2.0.2' and field and field.has_default() and created_separately:
-            return 'IntegerField'
-        return super(DatabaseFeatures, self).introspected_boolean_field_type(field, created_separately)
-
-
-class DatabaseOperations(BaseDatabaseOperations):
-    compiler_module = "django.db.backends.oracle.compiler"
-
-    # Oracle uses NUMBER(11) and NUMBER(19) for integer fields.
-    integer_field_ranges = {
-        'SmallIntegerField': (-99999999999, 99999999999),
-        'IntegerField': (-99999999999, 99999999999),
-        'BigIntegerField': (-9999999999999999999, 9999999999999999999),
-        'PositiveSmallIntegerField': (0, 99999999999),
-        'PositiveIntegerField': (0, 99999999999),
-    }
-
-    def autoinc_sql(self, table, column):
-        # To simulate auto-incrementing primary keys in Oracle, we have to
-        # create a sequence and a trigger.
-        sq_name = self._get_sequence_name(table)
-        tr_name = self._get_trigger_name(table)
-        tbl_name = self.quote_name(table)
-        col_name = self.quote_name(column)
-        sequence_sql = """
-DECLARE
-    i INTEGER;
-BEGIN
-    SELECT COUNT(*) INTO i FROM USER_CATALOG
-        WHERE TABLE_NAME = '%(sq_name)s' AND TABLE_TYPE = 'SEQUENCE';
-    IF i = 0 THEN
-        EXECUTE IMMEDIATE 'CREATE SEQUENCE "%(sq_name)s"';
-    END IF;
-END;
-/""" % locals()
-        trigger_sql = """
-CREATE OR REPLACE TRIGGER "%(tr_name)s"
-BEFORE INSERT ON %(tbl_name)s
-FOR EACH ROW
-WHEN (new.%(col_name)s IS NULL)
-    BEGIN
-        SELECT "%(sq_name)s".nextval
-        INTO :new.%(col_name)s FROM dual;
-    END;
-/""" % locals()
-        return sequence_sql, trigger_sql
-
-    def cache_key_culling_sql(self):
-        return """
-            SELECT cache_key
-              FROM (SELECT cache_key, rank() OVER (ORDER BY cache_key) AS rank FROM %s)
-             WHERE rank = %%s + 1
-        """
-
-    def date_extract_sql(self, lookup_type, field_name):
-        if lookup_type == 'week_day':
-            # TO_CHAR(field, 'D') returns an integer from 1-7, where 1=Sunday.
-            return "TO_CHAR(%s, 'D')" % field_name
-        else:
-            # http://docs.oracle.com/cd/B19306_01/server.102/b14200/functions050.htm
-            return "EXTRACT(%s FROM %s)" % (lookup_type.upper(), field_name)
-
-    def date_interval_sql(self, timedelta):
-        """
-        Implements the interval functionality for expressions
-        format for Oracle:
-        INTERVAL '3 00:03:20.000000' DAY(1) TO SECOND(6)
-        """
-        minutes, seconds = divmod(timedelta.seconds, 60)
-        hours, minutes = divmod(minutes, 60)
-        days = str(timedelta.days)
-        day_precision = len(days)
-        fmt = "INTERVAL '%s %02d:%02d:%02d.%06d' DAY(%d) TO SECOND(6)"
-        return fmt % (days, hours, minutes, seconds, timedelta.microseconds,
-                day_precision), []
-
-    def date_trunc_sql(self, lookup_type, field_name):
-        # http://docs.oracle.com/cd/B19306_01/server.102/b14200/functions230.htm#i1002084
-        if lookup_type in ('year', 'month'):
-            return "TRUNC(%s, '%s')" % (field_name, lookup_type.upper())
-        else:
-            return "TRUNC(%s)" % field_name
-
-    # Oracle crashes with "ORA-03113: end-of-file on communication channel"
-    # if the time zone name is passed in parameter. Use interpolation instead.
-    # https://groups.google.com/forum/#!msg/django-developers/zwQju7hbG78/9l934yelwfsJ
-    # This regexp matches all time zone names from the zoneinfo database.
-    _tzname_re = re.compile(r'^[\w/:+-]+$')
-
-    def _convert_field_to_tz(self, field_name, tzname):
-        if not self._tzname_re.match(tzname):
-            raise ValueError("Invalid time zone name: %s" % tzname)
-        # Convert from UTC to local time, returning TIMESTAMP WITH TIME ZONE.
-        result = "(FROM_TZ(%s, '0:00') AT TIME ZONE '%s')" % (field_name, tzname)
-        # Extracting from a TIMESTAMP WITH TIME ZONE ignore the time zone.
-        # Convert to a DATETIME, which is called DATE by Oracle. There's no
-        # built-in function to do that; the easiest is to go through a string.
-        result = "TO_CHAR(%s, 'YYYY-MM-DD HH24:MI:SS')" % result
-        result = "TO_DATE(%s, 'YYYY-MM-DD HH24:MI:SS')" % result
-        # Re-convert to a TIMESTAMP because EXTRACT only handles the date part
-        # on DATE values, even though they actually store the time part.
-        return "CAST(%s AS TIMESTAMP)" % result
-
-    def datetime_extract_sql(self, lookup_type, field_name, tzname):
-        if settings.USE_TZ:
-            field_name = self._convert_field_to_tz(field_name, tzname)
-        if lookup_type == 'week_day':
-            # TO_CHAR(field, 'D') returns an integer from 1-7, where 1=Sunday.
-            sql = "TO_CHAR(%s, 'D')" % field_name
-        else:
-            # http://docs.oracle.com/cd/B19306_01/server.102/b14200/functions050.htm
-            sql = "EXTRACT(%s FROM %s)" % (lookup_type.upper(), field_name)
-        return sql, []
-
-    def datetime_trunc_sql(self, lookup_type, field_name, tzname):
-        if settings.USE_TZ:
-            field_name = self._convert_field_to_tz(field_name, tzname)
-        # http://docs.oracle.com/cd/B19306_01/server.102/b14200/functions230.htm#i1002084
-        if lookup_type in ('year', 'month'):
-            sql = "TRUNC(%s, '%s')" % (field_name, lookup_type.upper())
-        elif lookup_type == 'day':
-            sql = "TRUNC(%s)" % field_name
-        elif lookup_type == 'hour':
-            sql = "TRUNC(%s, 'HH24')" % field_name
-        elif lookup_type == 'minute':
-            sql = "TRUNC(%s, 'MI')" % field_name
-        else:
-            sql = field_name    # Cast to DATE removes sub-second precision.
-        return sql, []
-
-    def get_db_converters(self, expression):
-        converters = super(DatabaseOperations, self).get_db_converters(expression)
-        internal_type = expression.output_field.get_internal_type()
-        if internal_type == 'TextField':
-            converters.append(self.convert_textfield_value)
-        elif internal_type == 'BinaryField':
-            converters.append(self.convert_binaryfield_value)
-        elif internal_type in ['BooleanField', 'NullBooleanField']:
-            converters.append(self.convert_booleanfield_value)
-        elif internal_type == 'DateField':
-            converters.append(self.convert_datefield_value)
-        elif internal_type == 'TimeField':
-            converters.append(self.convert_timefield_value)
-        elif internal_type == 'UUIDField':
-            converters.append(self.convert_uuidfield_value)
-        converters.append(self.convert_empty_values)
-        return converters
-
-    def convert_empty_values(self, value, expression, context):
-        # Oracle stores empty strings as null. We need to undo this in
-        # order to adhere to the Django convention of using the empty
-        # string instead of null, but only if the field accepts the
-        # empty string.
-        field = expression.output_field
-        if value is None and field.empty_strings_allowed:
-            value = ''
-            if field.get_internal_type() == 'BinaryField':
-                value = b''
-        return value
-
-    def convert_textfield_value(self, value, expression, context):
-        if isinstance(value, Database.LOB):
-            value = force_text(value.read())
-        return value
-
-    def convert_binaryfield_value(self, value, expression, context):
-        if isinstance(value, Database.LOB):
-            value = force_bytes(value.read())
-        return value
-
-    def convert_booleanfield_value(self, value, expression, context):
-        if value in (1, 0):
-            value = bool(value)
-        return value
-
-    # cx_Oracle always returns datetime.datetime objects for
-    # DATE and TIMESTAMP columns, but Django wants to see a
-    # python datetime.date, .time, or .datetime.
-    def convert_datefield_value(self, value, expression, context):
-        if isinstance(value, Database.Timestamp):
-            return value.date()
-
-    def convert_timefield_value(self, value, expression, context):
-        if isinstance(value, Database.Timestamp):
-            value = value.time()
-        return value
-
-    def convert_uuidfield_value(self, value, expression, context):
-        if value is not None:
-            value = uuid.UUID(value)
-        return value
-
-    def deferrable_sql(self):
-        return " DEFERRABLE INITIALLY DEFERRED"
-
-    def drop_sequence_sql(self, table):
-        return "DROP SEQUENCE %s;" % self.quote_name(self._get_sequence_name(table))
-
-    def fetch_returned_insert_id(self, cursor):
-        return int(cursor._insert_id_var.getvalue())
-
-    def field_cast_sql(self, db_type, internal_type):
-        if db_type and db_type.endswith('LOB'):
-            return "DBMS_LOB.SUBSTR(%s)"
-        else:
-            return "%s"
-
-    def last_executed_query(self, cursor, sql, params):
-        # http://cx-oracle.sourceforge.net/html/cursor.html#Cursor.statement
-        # The DB API definition does not define this attribute.
-        statement = cursor.statement
-        if statement and six.PY2 and not isinstance(statement, unicode):
-            statement = statement.decode('utf-8')
-        # Unlike Psycopg's `query` and MySQLdb`'s `_last_executed`, CxOracle's
-        # `statement` doesn't contain the query parameters. refs #20010.
-        return super(DatabaseOperations, self).last_executed_query(cursor, statement, params)
-
-    def last_insert_id(self, cursor, table_name, pk_name):
-        sq_name = self._get_sequence_name(table_name)
-        cursor.execute('SELECT "%s".currval FROM dual' % sq_name)
-        return cursor.fetchone()[0]
-
-    def lookup_cast(self, lookup_type):
-        if lookup_type in ('iexact', 'icontains', 'istartswith', 'iendswith'):
-            return "UPPER(%s)"
-        return "%s"
-
-    def max_in_list_size(self):
-        return 1000
-
-    def max_name_length(self):
-        return 30
-
-    def prep_for_iexact_query(self, x):
-        return x
-
-    def process_clob(self, value):
-        if value is None:
-            return ''
-        return force_text(value.read())
-
-    def quote_name(self, name):
-        # SQL92 requires delimited (quoted) names to be case-sensitive.  When
-        # not quoted, Oracle has case-insensitive behavior for identifiers, but
-        # always defaults to uppercase.
-        # We simplify things by making Oracle identifiers always uppercase.
-        if not name.startswith('"') and not name.endswith('"'):
-            name = '"%s"' % backend_utils.truncate_name(name.upper(),
-                                               self.max_name_length())
-        # Oracle puts the query text into a (query % args) construct, so % signs
-        # in names need to be escaped. The '%%' will be collapsed back to '%' at
-        # that stage so we aren't really making the name longer here.
-        name = name.replace('%', '%%')
-        return name.upper()
-
-    def random_function_sql(self):
-        return "DBMS_RANDOM.RANDOM"
-
-    def regex_lookup(self, lookup_type):
-        if lookup_type == 'regex':
-            match_option = "'c'"
-        else:
-            match_option = "'i'"
-        return 'REGEXP_LIKE(%%s, %%s, %s)' % match_option
-
-    def return_insert_id(self):
-        return "RETURNING %s INTO %%s", (InsertIdVar(),)
-
-    def savepoint_create_sql(self, sid):
-        return convert_unicode("SAVEPOINT " + self.quote_name(sid))
-
-    def savepoint_rollback_sql(self, sid):
-        return convert_unicode("ROLLBACK TO SAVEPOINT " + self.quote_name(sid))
-
-    def sql_flush(self, style, tables, sequences, allow_cascade=False):
-        # Return a list of 'TRUNCATE x;', 'TRUNCATE y;',
-        # 'TRUNCATE z;'... style SQL statements
-        if tables:
-            # Oracle does support TRUNCATE, but it seems to get us into
-            # FK referential trouble, whereas DELETE FROM table works.
-            sql = ['%s %s %s;' % (
-                style.SQL_KEYWORD('DELETE'),
-                style.SQL_KEYWORD('FROM'),
-                style.SQL_FIELD(self.quote_name(table))
-            ) for table in tables]
-            # Since we've just deleted all the rows, running our sequence
-            # ALTER code will reset the sequence to 0.
-            sql.extend(self.sequence_reset_by_name_sql(style, sequences))
-            return sql
-        else:
-            return []
-
-    def sequence_reset_by_name_sql(self, style, sequences):
-        sql = []
-        for sequence_info in sequences:
-            sequence_name = self._get_sequence_name(sequence_info['table'])
-            table_name = self.quote_name(sequence_info['table'])
-            column_name = self.quote_name(sequence_info['column'] or 'id')
-            query = _get_sequence_reset_sql() % {
-                'sequence': sequence_name,
-                'table': table_name,
-                'column': column_name,
-            }
-            sql.append(query)
-        return sql
-
-    def sequence_reset_sql(self, style, model_list):
-        from django.db import models
-        output = []
-        query = _get_sequence_reset_sql()
-        for model in model_list:
-            for f in model._meta.local_fields:
-                if isinstance(f, models.AutoField):
-                    table_name = self.quote_name(model._meta.db_table)
-                    sequence_name = self._get_sequence_name(model._meta.db_table)
-                    column_name = self.quote_name(f.column)
-                    output.append(query % {'sequence': sequence_name,
-                                           'table': table_name,
-                                           'column': column_name})
-                    # Only one AutoField is allowed per model, so don't
-                    # continue to loop
-                    break
-            for f in model._meta.many_to_many:
-                if not f.rel.through:
-                    table_name = self.quote_name(f.m2m_db_table())
-                    sequence_name = self._get_sequence_name(f.m2m_db_table())
-                    column_name = self.quote_name('id')
-                    output.append(query % {'sequence': sequence_name,
-                                           'table': table_name,
-                                           'column': column_name})
-        return output
-
-    def start_transaction_sql(self):
-        return ''
-
-    def tablespace_sql(self, tablespace, inline=False):
-        if inline:
-            return "USING INDEX TABLESPACE %s" % self.quote_name(tablespace)
-        else:
-            return "TABLESPACE %s" % self.quote_name(tablespace)
-
-    def value_to_db_date(self, value):
-        """
-        Transform a date value to an object compatible with what is expected
-        by the backend driver for date columns.
-        The default implementation transforms the date to text, but that is not
-        necessary for Oracle.
-        """
-        return value
-
-    def value_to_db_datetime(self, value):
-        """
-        Transform a datetime value to an object compatible with what is expected
-        by the backend driver for datetime columns.
-
-        If naive datetime is passed assumes that is in UTC. Normally Django
-        models.DateTimeField makes sure that if USE_TZ is True passed datetime
-        is timezone aware.
-        """
-
-        if value is None:
-            return None
-
-        # cx_Oracle doesn't support tz-aware datetimes
-        if timezone.is_aware(value):
-            if settings.USE_TZ:
-                value = value.astimezone(timezone.utc).replace(tzinfo=None)
-            else:
-                raise ValueError("Oracle backend does not support timezone-aware datetimes when USE_TZ is False.")
-
-        return Oracle_datetime.from_datetime(value)
-
-    def value_to_db_time(self, value):
-        if value is None:
-            return None
-
-        if isinstance(value, six.string_types):
-            return datetime.datetime.strptime(value, '%H:%M:%S')
-
-        # Oracle doesn't support tz-aware times
-        if timezone.is_aware(value):
-            raise ValueError("Oracle backend does not support timezone-aware times.")
-
-        return Oracle_datetime(1900, 1, 1, value.hour, value.minute,
-                               value.second, value.microsecond)
-
-    def year_lookup_bounds_for_date_field(self, value):
-        # Create bounds as real date values
-        first = datetime.date(value, 1, 1)
-        last = datetime.date(value, 12, 31)
-        return [first, last]
-
-    def year_lookup_bounds_for_datetime_field(self, value):
-        # cx_Oracle doesn't support tz-aware datetimes
-        bounds = super(DatabaseOperations, self).year_lookup_bounds_for_datetime_field(value)
-        if settings.USE_TZ:
-            bounds = [b.astimezone(timezone.utc) for b in bounds]
-        return [Oracle_datetime.from_datetime(b) for b in bounds]
-
-    def combine_expression(self, connector, sub_expressions):
-        "Oracle requires special cases for %% and & operators in query expressions"
-        if connector == '%%':
-            return 'MOD(%s)' % ','.join(sub_expressions)
-        elif connector == '&':
-            return 'BITAND(%s)' % ','.join(sub_expressions)
-        elif connector == '|':
-            raise NotImplementedError("Bit-wise or is not supported in Oracle.")
-        elif connector == '^':
-            return 'POWER(%s)' % ','.join(sub_expressions)
-        return super(DatabaseOperations, self).combine_expression(connector, sub_expressions)
-
-    def _get_sequence_name(self, table):
-        name_length = self.max_name_length() - 3
-        return '%s_SQ' % backend_utils.truncate_name(table, name_length).upper()
-
-    def _get_trigger_name(self, table):
-        name_length = self.max_name_length() - 3
-        return '%s_TR' % backend_utils.truncate_name(table, name_length).upper()
-
-    def bulk_insert_sql(self, fields, num_values):
-        items_sql = "SELECT %s FROM DUAL" % ", ".join(["%s"] * len(fields))
-        return " UNION ALL ".join([items_sql] * num_values)
-
 
 class _UninitializedOperatorsDescriptor(object):
 
@@ -897,19 +402,6 @@ class VariableWrapper(object):
             setattr(self.var, key, value)
 
 
-class InsertIdVar(object):
-    """
-    A late-binding cursor variable that can be passed to Cursor.execute
-    as a parameter, in order to receive the id of the row created by an
-    insert statement.
-    """
-
-    def bind_parameter(self, cursor):
-        param = cursor.cursor.var(Database.NUMBER)
-        cursor._insert_id_var = param
-        return param
-
-
 class FormatStylePlaceholderCursor(object):
     """
     Django uses "format" (e.g. '%s') style placeholders, but Oracle uses ":var"
@@ -1117,20 +609,3 @@ def to_unicode(s):
     if isinstance(s, six.string_types):
         return force_text(s)
     return s
-
-
-def _get_sequence_reset_sql():
-    # TODO: colorize this SQL code with style.SQL_KEYWORD(), etc.
-    return """
-DECLARE
-    table_value integer;
-    seq_value integer;
-BEGIN
-    SELECT NVL(MAX(%(column)s), 0) INTO table_value FROM %(table)s;
-    SELECT NVL(last_number - cache_size, 0) INTO seq_value FROM user_sequences
-           WHERE sequence_name = '%(sequence)s';
-    WHILE table_value > seq_value LOOP
-        SELECT "%(sequence)s".nextval INTO seq_value FROM dual;
-    END LOOP;
-END;
-/"""

django/db/backends/oracle/client.py

@@ -1,6 +1,6 @@
 import subprocess
 
-from django.db.backends import BaseDatabaseClient
+from django.db.backends.base.client import BaseDatabaseClient
 
 
 class DatabaseClient(BaseDatabaseClient):

django/db/backends/oracle/creation.py

@@ -2,7 +2,7 @@ import sys
 import time
 
 from django.conf import settings
-from django.db.backends.creation import BaseDatabaseCreation
+from django.db.backends.base.creation import BaseDatabaseCreation
 from django.db.utils import DatabaseError
 from django.utils.six.moves import input
 

django/db/backends/oracle/features.py

@@ -0,0 +1,57 @@
+from django.db.backends.base.features import BaseDatabaseFeatures
+from django.db.utils import InterfaceError
+
+try:
+    import pytz
+except ImportError:
+    pytz = None
+
+
+class DatabaseFeatures(BaseDatabaseFeatures):
+    empty_fetchmany_value = ()
+    needs_datetime_string_cast = False
+    interprets_empty_strings_as_nulls = True
+    uses_savepoints = True
+    has_select_for_update = True
+    has_select_for_update_nowait = True
+    can_return_id_from_insert = True
+    allow_sliced_subqueries = False
+    supports_subqueries_in_group_by = False
+    supports_transactions = True
+    supports_timezones = False
+    has_zoneinfo_database = pytz is not None
+    supports_bitwise_or = False
+    has_native_duration_field = True
+    can_defer_constraint_checks = True
+    supports_partially_nullable_unique_constraints = False
+    truncates_names = True
+    has_bulk_insert = True
+    supports_tablespaces = True
+    supports_sequence_reset = False
+    can_introspect_max_length = False
+    can_introspect_time_field = False
+    atomic_transactions = False
+    supports_combined_alters = False
+    nulls_order_largest = True
+    requires_literal_defaults = True
+    connection_persists_old_columns = True
+    closed_cursor_error_class = InterfaceError
+    bare_select_suffix = " FROM DUAL"
+    uppercases_column_names = True
+    # select for update with limit can be achieved on Oracle, but not with the current backend.
+    supports_select_for_update_with_limit = False
+
+    def introspected_boolean_field_type(self, field=None, created_separately=False):
+        """
+        Some versions of Oracle -- we've seen this on 11.2.0.1 and suspect
+        it goes back -- have a weird bug where, when an integer column is
+        added to an existing table with a default, its precision is later
+        reported on introspection as 0, regardless of the real precision.
+        For Django introspection, this means that such columns are reported
+        as IntegerField even if they are really BigIntegerField or BooleanField.
+
+        The bug is solved in Oracle 11.2.0.2 and up.
+        """
+        if self.connection.oracle_full_version < '11.2.0.2' and field and field.has_default() and created_separately:
+            return 'IntegerField'
+        return super(DatabaseFeatures, self).introspected_boolean_field_type(field, created_separately)

django/db/backends/oracle/introspection.py

@@ -2,7 +2,9 @@ import re
 
 import cx_Oracle
 
-from django.db.backends import BaseDatabaseIntrospection, FieldInfo, TableInfo
+from django.db.backends.base.introspection import (
+    BaseDatabaseIntrospection, FieldInfo, TableInfo,
+)
 from django.utils.encoding import force_text
 
 foreign_key_re = re.compile(r"\sCONSTRAINT `[^`]*` FOREIGN KEY \(`([^`]*)`\) REFERENCES `([^`]*)` \(`([^`]*)`\)")

django/db/backends/oracle/operations.py

@@ -0,0 +1,447 @@
+from __future__ import unicode_literals
+
+import datetime
+import re
+import uuid
+
+from django.conf import settings
+from django.db.backends.base.operations import BaseDatabaseOperations
+from django.db.backends.utils import truncate_name
+from django.utils import six, timezone
+from django.utils.encoding import force_bytes, force_text
+
+from .base import Database
+from .utils import convert_unicode, InsertIdVar, Oracle_datetime
+
+
+class DatabaseOperations(BaseDatabaseOperations):
+    compiler_module = "django.db.backends.oracle.compiler"
+
+    # Oracle uses NUMBER(11) and NUMBER(19) for integer fields.
+    integer_field_ranges = {
+        'SmallIntegerField': (-99999999999, 99999999999),
+        'IntegerField': (-99999999999, 99999999999),
+        'BigIntegerField': (-9999999999999999999, 9999999999999999999),
+        'PositiveSmallIntegerField': (0, 99999999999),
+        'PositiveIntegerField': (0, 99999999999),
+    }
+
+    # TODO: colorize this SQL code with style.SQL_KEYWORD(), etc.
+    _sequence_reset_sql = """
+DECLARE
+    table_value integer;
+    seq_value integer;
+BEGIN
+    SELECT NVL(MAX(%(column)s), 0) INTO table_value FROM %(table)s;
+    SELECT NVL(last_number - cache_size, 0) INTO seq_value FROM user_sequences
+           WHERE sequence_name = '%(sequence)s';
+    WHILE table_value > seq_value LOOP
+        SELECT "%(sequence)s".nextval INTO seq_value FROM dual;
+    END LOOP;
+END;
+/"""
+
+    def autoinc_sql(self, table, column):
+        # To simulate auto-incrementing primary keys in Oracle, we have to
+        # create a sequence and a trigger.
+        sq_name = self._get_sequence_name(table)
+        tr_name = self._get_trigger_name(table)
+        tbl_name = self.quote_name(table)
+        col_name = self.quote_name(column)
+        sequence_sql = """
+DECLARE
+    i INTEGER;
+BEGIN
+    SELECT COUNT(*) INTO i FROM USER_CATALOG
+        WHERE TABLE_NAME = '%(sq_name)s' AND TABLE_TYPE = 'SEQUENCE';
+    IF i = 0 THEN
+        EXECUTE IMMEDIATE 'CREATE SEQUENCE "%(sq_name)s"';
+    END IF;
+END;
+/""" % locals()
+        trigger_sql = """
+CREATE OR REPLACE TRIGGER "%(tr_name)s"
+BEFORE INSERT ON %(tbl_name)s
+FOR EACH ROW
+WHEN (new.%(col_name)s IS NULL)
+    BEGIN
+        SELECT "%(sq_name)s".nextval
+        INTO :new.%(col_name)s FROM dual;
+    END;
+/""" % locals()
+        return sequence_sql, trigger_sql
+
+    def cache_key_culling_sql(self):
+        return """
+            SELECT cache_key
+              FROM (SELECT cache_key, rank() OVER (ORDER BY cache_key) AS rank FROM %s)
+             WHERE rank = %%s + 1
+        """
+
+    def date_extract_sql(self, lookup_type, field_name):
+        if lookup_type == 'week_day':
+            # TO_CHAR(field, 'D') returns an integer from 1-7, where 1=Sunday.
+            return "TO_CHAR(%s, 'D')" % field_name
+        else:
+            # http://docs.oracle.com/cd/B19306_01/server.102/b14200/functions050.htm
+            return "EXTRACT(%s FROM %s)" % (lookup_type.upper(), field_name)
+
+    def date_interval_sql(self, timedelta):
+        """
+        Implements the interval functionality for expressions
+        format for Oracle:
+        INTERVAL '3 00:03:20.000000' DAY(1) TO SECOND(6)
+        """
+        minutes, seconds = divmod(timedelta.seconds, 60)
+        hours, minutes = divmod(minutes, 60)
+        days = str(timedelta.days)
+        day_precision = len(days)
+        fmt = "INTERVAL '%s %02d:%02d:%02d.%06d' DAY(%d) TO SECOND(6)"
+        return fmt % (days, hours, minutes, seconds, timedelta.microseconds,
+                day_precision), []
+
+    def date_trunc_sql(self, lookup_type, field_name):
+        # http://docs.oracle.com/cd/B19306_01/server.102/b14200/functions230.htm#i1002084
+        if lookup_type in ('year', 'month'):
+            return "TRUNC(%s, '%s')" % (field_name, lookup_type.upper())
+        else:
+            return "TRUNC(%s)" % field_name
+
+    # Oracle crashes with "ORA-03113: end-of-file on communication channel"
+    # if the time zone name is passed in parameter. Use interpolation instead.
+    # https://groups.google.com/forum/#!msg/django-developers/zwQju7hbG78/9l934yelwfsJ
+    # This regexp matches all time zone names from the zoneinfo database.
+    _tzname_re = re.compile(r'^[\w/:+-]+$')
+
+    def _convert_field_to_tz(self, field_name, tzname):
+        if not self._tzname_re.match(tzname):
+            raise ValueError("Invalid time zone name: %s" % tzname)
+        # Convert from UTC to local time, returning TIMESTAMP WITH TIME ZONE.
+        result = "(FROM_TZ(%s, '0:00') AT TIME ZONE '%s')" % (field_name, tzname)
+        # Extracting from a TIMESTAMP WITH TIME ZONE ignore the time zone.
+        # Convert to a DATETIME, which is called DATE by Oracle. There's no
+        # built-in function to do that; the easiest is to go through a string.
+        result = "TO_CHAR(%s, 'YYYY-MM-DD HH24:MI:SS')" % result
+        result = "TO_DATE(%s, 'YYYY-MM-DD HH24:MI:SS')" % result
+        # Re-convert to a TIMESTAMP because EXTRACT only handles the date part
+        # on DATE values, even though they actually store the time part.
+        return "CAST(%s AS TIMESTAMP)" % result
+
+    def datetime_extract_sql(self, lookup_type, field_name, tzname):
+        if settings.USE_TZ:
+            field_name = self._convert_field_to_tz(field_name, tzname)
+        if lookup_type == 'week_day':
+            # TO_CHAR(field, 'D') returns an integer from 1-7, where 1=Sunday.
+            sql = "TO_CHAR(%s, 'D')" % field_name
+        else:
+            # http://docs.oracle.com/cd/B19306_01/server.102/b14200/functions050.htm
+            sql = "EXTRACT(%s FROM %s)" % (lookup_type.upper(), field_name)
+        return sql, []
+
+    def datetime_trunc_sql(self, lookup_type, field_name, tzname):
+        if settings.USE_TZ:
+            field_name = self._convert_field_to_tz(field_name, tzname)
+        # http://docs.oracle.com/cd/B19306_01/server.102/b14200/functions230.htm#i1002084
+        if lookup_type in ('year', 'month'):
+            sql = "TRUNC(%s, '%s')" % (field_name, lookup_type.upper())
+        elif lookup_type == 'day':
+            sql = "TRUNC(%s)" % field_name
+        elif lookup_type == 'hour':
+            sql = "TRUNC(%s, 'HH24')" % field_name
+        elif lookup_type == 'minute':
+            sql = "TRUNC(%s, 'MI')" % field_name
+        else:
+            sql = field_name    # Cast to DATE removes sub-second precision.
+        return sql, []
+
+    def get_db_converters(self, expression):
+        converters = super(DatabaseOperations, self).get_db_converters(expression)
+        internal_type = expression.output_field.get_internal_type()
+        if internal_type == 'TextField':
+            converters.append(self.convert_textfield_value)
+        elif internal_type == 'BinaryField':
+            converters.append(self.convert_binaryfield_value)
+        elif internal_type in ['BooleanField', 'NullBooleanField']:
+            converters.append(self.convert_booleanfield_value)
+        elif internal_type == 'DateField':
+            converters.append(self.convert_datefield_value)
+        elif internal_type == 'TimeField':
+            converters.append(self.convert_timefield_value)
+        elif internal_type == 'UUIDField':
+            converters.append(self.convert_uuidfield_value)
+        converters.append(self.convert_empty_values)
+        return converters
+
+    def convert_empty_values(self, value, expression, context):
+        # Oracle stores empty strings as null. We need to undo this in
+        # order to adhere to the Django convention of using the empty
+        # string instead of null, but only if the field accepts the
+        # empty string.
+        field = expression.output_field
+        if value is None and field.empty_strings_allowed:
+            value = ''
+            if field.get_internal_type() == 'BinaryField':
+                value = b''
+        return value
+
+    def convert_textfield_value(self, value, expression, context):
+        if isinstance(value, Database.LOB):
+            value = force_text(value.read())
+        return value
+
+    def convert_binaryfield_value(self, value, expression, context):
+        if isinstance(value, Database.LOB):
+            value = force_bytes(value.read())
+        return value
+
+    def convert_booleanfield_value(self, value, expression, context):
+        if value in (1, 0):
+            value = bool(value)
+        return value
+
+    # cx_Oracle always returns datetime.datetime objects for
+    # DATE and TIMESTAMP columns, but Django wants to see a
+    # python datetime.date, .time, or .datetime.
+    def convert_datefield_value(self, value, expression, context):
+        if isinstance(value, Database.Timestamp):
+            return value.date()
+
+    def convert_timefield_value(self, value, expression, context):
+        if isinstance(value, Database.Timestamp):
+            value = value.time()
+        return value
+
+    def convert_uuidfield_value(self, value, expression, context):
+        if value is not None:
+            value = uuid.UUID(value)
+        return value
+
+    def deferrable_sql(self):
+        return " DEFERRABLE INITIALLY DEFERRED"
+
+    def drop_sequence_sql(self, table):
+        return "DROP SEQUENCE %s;" % self.quote_name(self._get_sequence_name(table))
+
+    def fetch_returned_insert_id(self, cursor):
+        return int(cursor._insert_id_var.getvalue())
+
+    def field_cast_sql(self, db_type, internal_type):
+        if db_type and db_type.endswith('LOB'):
+            return "DBMS_LOB.SUBSTR(%s)"
+        else:
+            return "%s"
+
+    def last_executed_query(self, cursor, sql, params):
+        # http://cx-oracle.sourceforge.net/html/cursor.html#Cursor.statement
+        # The DB API definition does not define this attribute.
+        statement = cursor.statement
+        if statement and six.PY2 and not isinstance(statement, unicode):
+            statement = statement.decode('utf-8')
+        # Unlike Psycopg's `query` and MySQLdb`'s `_last_executed`, CxOracle's
+        # `statement` doesn't contain the query parameters. refs #20010.
+        return super(DatabaseOperations, self).last_executed_query(cursor, statement, params)
+
+    def last_insert_id(self, cursor, table_name, pk_name):
+        sq_name = self._get_sequence_name(table_name)
+        cursor.execute('SELECT "%s".currval FROM dual' % sq_name)
+        return cursor.fetchone()[0]
+
+    def lookup_cast(self, lookup_type):
+        if lookup_type in ('iexact', 'icontains', 'istartswith', 'iendswith'):
+            return "UPPER(%s)"
+        return "%s"
+
+    def max_in_list_size(self):
+        return 1000
+
+    def max_name_length(self):
+        return 30
+
+    def prep_for_iexact_query(self, x):
+        return x
+
+    def process_clob(self, value):
+        if value is None:
+            return ''
+        return force_text(value.read())
+
+    def quote_name(self, name):
+        # SQL92 requires delimited (quoted) names to be case-sensitive.  When
+        # not quoted, Oracle has case-insensitive behavior for identifiers, but
+        # always defaults to uppercase.
+        # We simplify things by making Oracle identifiers always uppercase.
+        if not name.startswith('"') and not name.endswith('"'):
+            name = '"%s"' % truncate_name(name.upper(), self.max_name_length())
+        # Oracle puts the query text into a (query % args) construct, so % signs
+        # in names need to be escaped. The '%%' will be collapsed back to '%' at
+        # that stage so we aren't really making the name longer here.
+        name = name.replace('%', '%%')
+        return name.upper()
+
+    def random_function_sql(self):
+        return "DBMS_RANDOM.RANDOM"
+
+    def regex_lookup(self, lookup_type):
+        if lookup_type == 'regex':
+            match_option = "'c'"
+        else:
+            match_option = "'i'"
+        return 'REGEXP_LIKE(%%s, %%s, %s)' % match_option
+
+    def return_insert_id(self):
+        return "RETURNING %s INTO %%s", (InsertIdVar(),)
+
+    def savepoint_create_sql(self, sid):
+        return convert_unicode("SAVEPOINT " + self.quote_name(sid))
+
+    def savepoint_rollback_sql(self, sid):
+        return convert_unicode("ROLLBACK TO SAVEPOINT " + self.quote_name(sid))
+
+    def sql_flush(self, style, tables, sequences, allow_cascade=False):
+        # Return a list of 'TRUNCATE x;', 'TRUNCATE y;',
+        # 'TRUNCATE z;'... style SQL statements
+        if tables:
+            # Oracle does support TRUNCATE, but it seems to get us into
+            # FK referential trouble, whereas DELETE FROM table works.
+            sql = ['%s %s %s;' % (
+                style.SQL_KEYWORD('DELETE'),
+                style.SQL_KEYWORD('FROM'),
+                style.SQL_FIELD(self.quote_name(table))
+            ) for table in tables]
+            # Since we've just deleted all the rows, running our sequence
+            # ALTER code will reset the sequence to 0.
+            sql.extend(self.sequence_reset_by_name_sql(style, sequences))
+            return sql
+        else:
+            return []
+
+    def sequence_reset_by_name_sql(self, style, sequences):
+        sql = []
+        for sequence_info in sequences:
+            sequence_name = self._get_sequence_name(sequence_info['table'])
+            table_name = self.quote_name(sequence_info['table'])
+            column_name = self.quote_name(sequence_info['column'] or 'id')
+            query = self._sequence_reset_sql % {
+                'sequence': sequence_name,
+                'table': table_name,
+                'column': column_name,
+            }
+            sql.append(query)
+        return sql
+
+    def sequence_reset_sql(self, style, model_list):
+        from django.db import models
+        output = []
+        query = self._sequence_reset_sql
+        for model in model_list:
+            for f in model._meta.local_fields:
+                if isinstance(f, models.AutoField):
+                    table_name = self.quote_name(model._meta.db_table)
+                    sequence_name = self._get_sequence_name(model._meta.db_table)
+                    column_name = self.quote_name(f.column)
+                    output.append(query % {'sequence': sequence_name,
+                                           'table': table_name,
+                                           'column': column_name})
+                    # Only one AutoField is allowed per model, so don't
+                    # continue to loop
+                    break
+            for f in model._meta.many_to_many:
+                if not f.rel.through:
+                    table_name = self.quote_name(f.m2m_db_table())
+                    sequence_name = self._get_sequence_name(f.m2m_db_table())
+                    column_name = self.quote_name('id')
+                    output.append(query % {'sequence': sequence_name,
+                                           'table': table_name,
+                                           'column': column_name})
+        return output
+
+    def start_transaction_sql(self):
+        return ''
+
+    def tablespace_sql(self, tablespace, inline=False):
+        if inline:
+            return "USING INDEX TABLESPACE %s" % self.quote_name(tablespace)
+        else:
+            return "TABLESPACE %s" % self.quote_name(tablespace)
+
+    def value_to_db_date(self, value):
+        """
+        Transform a date value to an object compatible with what is expected
+        by the backend driver for date columns.
+        The default implementation transforms the date to text, but that is not
+        necessary for Oracle.
+        """
+        return value
+
+    def value_to_db_datetime(self, value):
+        """
+        Transform a datetime value to an object compatible with what is expected
+        by the backend driver for datetime columns.
+
+        If naive datetime is passed assumes that is in UTC. Normally Django
+        models.DateTimeField makes sure that if USE_TZ is True passed datetime
+        is timezone aware.
+        """
+
+        if value is None:
+            return None
+
+        # cx_Oracle doesn't support tz-aware datetimes
+        if timezone.is_aware(value):
+            if settings.USE_TZ:
+                value = value.astimezone(timezone.utc).replace(tzinfo=None)
+            else:
+                raise ValueError("Oracle backend does not support timezone-aware datetimes when USE_TZ is False.")
+
+        return Oracle_datetime.from_datetime(value)
+
+    def value_to_db_time(self, value):
+        if value is None:
+            return None
+
+        if isinstance(value, six.string_types):
+            return datetime.datetime.strptime(value, '%H:%M:%S')
+
+        # Oracle doesn't support tz-aware times
+        if timezone.is_aware(value):
+            raise ValueError("Oracle backend does not support timezone-aware times.")
+
+        return Oracle_datetime(1900, 1, 1, value.hour, value.minute,
+                               value.second, value.microsecond)
+
+    def year_lookup_bounds_for_date_field(self, value):
+        # Create bounds as real date values
+        first = datetime.date(value, 1, 1)
+        last = datetime.date(value, 12, 31)
+        return [first, last]
+
+    def year_lookup_bounds_for_datetime_field(self, value):
+        # cx_Oracle doesn't support tz-aware datetimes
+        bounds = super(DatabaseOperations, self).year_lookup_bounds_for_datetime_field(value)
+        if settings.USE_TZ:
+            bounds = [b.astimezone(timezone.utc) for b in bounds]
+        return [Oracle_datetime.from_datetime(b) for b in bounds]
+
+    def combine_expression(self, connector, sub_expressions):
+        "Oracle requires special cases for %% and & operators in query expressions"
+        if connector == '%%':
+            return 'MOD(%s)' % ','.join(sub_expressions)
+        elif connector == '&':
+            return 'BITAND(%s)' % ','.join(sub_expressions)
+        elif connector == '|':
+            raise NotImplementedError("Bit-wise or is not supported in Oracle.")
+        elif connector == '^':
+            return 'POWER(%s)' % ','.join(sub_expressions)
+        return super(DatabaseOperations, self).combine_expression(connector, sub_expressions)
+
+    def _get_sequence_name(self, table):
+        name_length = self.max_name_length() - 3
+        return '%s_SQ' % truncate_name(table, name_length).upper()
+
+    def _get_trigger_name(self, table):
+        name_length = self.max_name_length() - 3
+        return '%s_TR' % truncate_name(table, name_length).upper()
+
+    def bulk_insert_sql(self, fields, num_values):
+        items_sql = "SELECT %s FROM DUAL" % ", ".join(["%s"] * len(fields))
+        return " UNION ALL ".join([items_sql] * num_values)

django/db/backends/oracle/schema.py

@@ -4,7 +4,7 @@ import binascii
 
 from django.utils import six
 from django.utils.text import force_text
-from django.db.backends.schema import BaseDatabaseSchemaEditor
+from django.db.backends.base.schema import BaseDatabaseSchemaEditor
 from django.db.utils import DatabaseError
 
 

django/db/backends/oracle/utils.py

@@ -0,0 +1,42 @@
+import datetime
+
+from django.utils.encoding import force_bytes, force_text
+
+from .base import Database
+
+# Check whether cx_Oracle was compiled with the WITH_UNICODE option if cx_Oracle is pre-5.1. This will
+# also be True for cx_Oracle 5.1 and in Python 3.0. See #19606
+if int(Database.version.split('.', 1)[0]) >= 5 and \
+        (int(Database.version.split('.', 2)[1]) >= 1 or
+         not hasattr(Database, 'UNICODE')):
+    convert_unicode = force_text
+else:
+    convert_unicode = force_bytes
+
+
+class InsertIdVar(object):
+    """
+    A late-binding cursor variable that can be passed to Cursor.execute
+    as a parameter, in order to receive the id of the row created by an
+    insert statement.
+    """
+
+    def bind_parameter(self, cursor):
+        param = cursor.cursor.var(Database.NUMBER)
+        cursor._insert_id_var = param
+        return param
+
+
+class Oracle_datetime(datetime.datetime):
+    """
+    A datetime object, with an additional class attribute
+    to tell cx_Oracle to save the microseconds too.
+    """
+    input_size = Database.TIMESTAMP
+
+    @classmethod
+    def from_datetime(cls, dt):
+        return Oracle_datetime(
+            dt.year, dt.month, dt.day,
+            dt.hour, dt.minute, dt.second, dt.microsecond,
+        )

django/db/backends/postgresql_psycopg2/base.py

@@ -5,19 +5,11 @@ Requires psycopg 2: http://initd.org/projects/psycopg2
 """
 
 from django.conf import settings
-from django.db.backends import (BaseDatabaseFeatures, BaseDatabaseWrapper,
-    BaseDatabaseValidation)
-from django.db.backends.postgresql_psycopg2.operations import DatabaseOperations
-from django.db.backends.postgresql_psycopg2.client import DatabaseClient
-from django.db.backends.postgresql_psycopg2.creation import DatabaseCreation
-from django.db.backends.postgresql_psycopg2.version import get_version
-from django.db.backends.postgresql_psycopg2.introspection import DatabaseIntrospection
-from django.db.backends.postgresql_psycopg2.schema import DatabaseSchemaEditor
-from django.db.utils import InterfaceError
+from django.db.backends.base.base import BaseDatabaseWrapper
+from django.db.backends.base.validation import BaseDatabaseValidation
 from django.utils.encoding import force_str
 from django.utils.functional import cached_property
 from django.utils.safestring import SafeText, SafeBytes
-from django.utils.timezone import utc
 
 try:
     import psycopg2 as Database
@@ -27,6 +19,16 @@ except ImportError as e:
     from django.core.exceptions import ImproperlyConfigured
     raise ImproperlyConfigured("Error loading psycopg2 module: %s" % e)
 
+# Some of these import psycopg2, so import them after checking if it's installed.
+from .client import DatabaseClient
+from .creation import DatabaseCreation
+from .features import DatabaseFeatures
+from .introspection import DatabaseIntrospection
+from .operations import DatabaseOperations
+from .schema import DatabaseSchemaEditor
+from .utils import utc_tzinfo_factory
+from .version import get_version
+
 DatabaseError = Database.DatabaseError
 IntegrityError = Database.IntegrityError
 
@@ -37,38 +39,6 @@ psycopg2.extensions.register_adapter(SafeText, psycopg2.extensions.QuotedString)
 psycopg2.extras.register_uuid()
 
 
-def utc_tzinfo_factory(offset):
-    if offset != 0:
-        raise AssertionError("database connection isn't set to UTC")
-    return utc
-
-
-class DatabaseFeatures(BaseDatabaseFeatures):
-    needs_datetime_string_cast = False
-    can_return_id_from_insert = True
-    has_real_datatype = True
-    has_native_duration_field = True
-    driver_supports_timedelta_args = True
-    can_defer_constraint_checks = True
-    has_select_for_update = True
-    has_select_for_update_nowait = True
-    has_bulk_insert = True
-    uses_savepoints = True
-    can_release_savepoints = True
-    supports_tablespaces = True
-    supports_transactions = True
-    can_introspect_autofield = True
-    can_introspect_ip_address_field = True
-    can_introspect_small_integer_field = True
-    can_distinct_on_fields = True
-    can_rollback_ddl = True
-    supports_combined_alters = True
-    nulls_order_largest = True
-    closed_cursor_error_class = InterfaceError
-    has_case_insensitive_like = False
-    requires_sqlparse_for_splitting = False
-
-
 class DatabaseWrapper(BaseDatabaseWrapper):
     vendor = 'postgresql'
     # This dictionary maps Field objects to their associated PostgreSQL column

django/db/backends/postgresql_psycopg2/client.py

@@ -1,6 +1,6 @@
 import subprocess
 
-from django.db.backends import BaseDatabaseClient
+from django.db.backends.base.client import BaseDatabaseClient
 
 
 class DatabaseClient(BaseDatabaseClient):

django/db/backends/postgresql_psycopg2/creation.py

@@ -1,4 +1,4 @@
-from django.db.backends.creation import BaseDatabaseCreation
+from django.db.backends.base.creation import BaseDatabaseCreation
 from django.db.backends.utils import truncate_name
 
 

django/db/backends/postgresql_psycopg2/features.py

@@ -0,0 +1,28 @@
+from django.db.backends.base.features import BaseDatabaseFeatures
+from django.db.utils import InterfaceError
+
+
+class DatabaseFeatures(BaseDatabaseFeatures):
+    needs_datetime_string_cast = False
+    can_return_id_from_insert = True
+    has_real_datatype = True
+    has_native_duration_field = True
+    driver_supports_timedelta_args = True
+    can_defer_constraint_checks = True
+    has_select_for_update = True
+    has_select_for_update_nowait = True
+    has_bulk_insert = True
+    uses_savepoints = True
+    can_release_savepoints = True
+    supports_tablespaces = True
+    supports_transactions = True
+    can_introspect_autofield = True
+    can_introspect_ip_address_field = True
+    can_introspect_small_integer_field = True
+    can_distinct_on_fields = True
+    can_rollback_ddl = True
+    supports_combined_alters = True
+    nulls_order_largest = True
+    closed_cursor_error_class = InterfaceError
+    has_case_insensitive_like = False
+    requires_sqlparse_for_splitting = False

django/db/backends/postgresql_psycopg2/introspection.py

@@ -1,7 +1,9 @@
 from __future__ import unicode_literals
 from collections import namedtuple
 
-from django.db.backends import BaseDatabaseIntrospection, FieldInfo, TableInfo
+from django.db.backends.base.introspection import (
+    BaseDatabaseIntrospection, FieldInfo, TableInfo,
+)
 from django.utils.encoding import force_text
 
 

django/db/backends/postgresql_psycopg2/operations.py

@@ -1,7 +1,7 @@
 from __future__ import unicode_literals
 
 from django.conf import settings
-from django.db.backends import BaseDatabaseOperations
+from django.db.backends.base.operations import BaseDatabaseOperations
 
 
 class DatabaseOperations(BaseDatabaseOperations):

django/db/backends/postgresql_psycopg2/schema.py

@@ -1,4 +1,6 @@
-from django.db.backends.schema import BaseDatabaseSchemaEditor
+from django.db.backends.base.schema import BaseDatabaseSchemaEditor
+
+import psycopg2
 
 
 class DatabaseSchemaEditor(BaseDatabaseSchemaEditor):
@@ -10,8 +12,6 @@ class DatabaseSchemaEditor(BaseDatabaseSchemaEditor):
     sql_create_text_index = "CREATE INDEX %(name)s ON %(table)s (%(columns)s text_pattern_ops)%(extra)s"
 
     def quote_value(self, value):
-        # Inner import so backend fails nicely if it's not present
-        import psycopg2
         return psycopg2.extensions.adapt(value)
 
     def _model_indexes_sql(self, model):

django/db/backends/postgresql_psycopg2/utils.py

@@ -0,0 +1,7 @@
+from django.utils.timezone import utc
+
+
+def utc_tzinfo_factory(offset):
+    if offset != 0:
+        raise AssertionError("database connection isn't set to UTC")
+    return utc

django/db/backends/sqlite3/base.py

@@ -9,26 +9,22 @@ from __future__ import unicode_literals
 import datetime
 import decimal
 import re
-import sys
-import uuid
 import warnings
 
 from django.conf import settings
 from django.db import utils
-from django.db.backends import (utils as backend_utils, BaseDatabaseFeatures,
-    BaseDatabaseOperations, BaseDatabaseWrapper, BaseDatabaseValidation)
-from django.db.backends.sqlite3.client import DatabaseClient
-from django.db.backends.sqlite3.creation import DatabaseCreation
-from django.db.backends.sqlite3.introspection import DatabaseIntrospection
-from django.db.backends.sqlite3.schema import DatabaseSchemaEditor
-from django.db.models import fields, aggregates
-from django.utils.dateparse import parse_date, parse_datetime, parse_time, parse_duration
-from django.utils.duration import duration_string
+from django.db.backends import utils as backend_utils
+from django.db.backends.base.base import BaseDatabaseWrapper
+from django.db.backends.base.validation import BaseDatabaseValidation
+from django.utils import six, timezone
+from django.utils.dateparse import parse_date, parse_duration, parse_time
 from django.utils.encoding import force_text
-from django.utils.functional import cached_property
 from django.utils.safestring import SafeBytes
-from django.utils import six
-from django.utils import timezone
+
+try:
+    import pytz
+except ImportError:
+    pytz = None
 
 try:
     try:
@@ -39,23 +35,19 @@ except ImportError as exc:
     from django.core.exceptions import ImproperlyConfigured
     raise ImproperlyConfigured("Error loading either pysqlite2 or sqlite3 modules (tried in that order): %s" % exc)
 
-try:
-    import pytz
-except ImportError:
-    pytz = None
+# Some of these import sqlite3, so import them after checking if it's installed.
+from .client import DatabaseClient
+from .creation import DatabaseCreation
+from .features import DatabaseFeatures
+from .introspection import DatabaseIntrospection
+from .operations import DatabaseOperations
+from .schema import DatabaseSchemaEditor
+from .utils import parse_datetime_with_timezone_support
 
 DatabaseError = Database.DatabaseError
 IntegrityError = Database.IntegrityError
 
 
-def parse_datetime_with_timezone_support(value):
-    dt = parse_datetime(value)
-    # Confirm that dt is naive before overwriting its tzinfo.
-    if dt is not None and settings.USE_TZ and timezone.is_naive(dt):
-        dt = dt.replace(tzinfo=timezone.utc)
-    return dt
-
-
 def adapt_datetime_with_timezone_support(value):
     # Equivalent to DateTimeField.get_db_prep_value. Used only by raw SQL.
     if settings.USE_TZ:
@@ -91,250 +83,6 @@ if six.PY2:
     Database.register_adapter(SafeBytes, lambda s: s.decode('utf-8'))
 
 
-class DatabaseFeatures(BaseDatabaseFeatures):
-    # SQLite cannot handle us only partially reading from a cursor's result set
-    # and then writing the same rows to the database in another cursor. This
-    # setting ensures we always read result sets fully into memory all in one
-    # go.
-    can_use_chunked_reads = False
-    test_db_allows_multiple_connections = False
-    supports_unspecified_pk = True
-    supports_timezones = False
-    supports_1000_query_parameters = False
-    supports_mixed_date_datetime_comparisons = False
-    has_bulk_insert = True
-    can_combine_inserts_with_and_without_auto_increment_pk = False
-    supports_foreign_keys = False
-    supports_column_check_constraints = False
-    autocommits_when_autocommit_is_off = True
-    can_introspect_decimal_field = False
-    can_introspect_positive_integer_field = True
-    can_introspect_small_integer_field = True
-    supports_transactions = True
-    atomic_transactions = False
-    can_rollback_ddl = True
-    supports_paramstyle_pyformat = False
-    supports_sequence_reset = False
-
-    @cached_property
-    def uses_savepoints(self):
-        return Database.sqlite_version_info >= (3, 6, 8)
-
-    @cached_property
-    def can_release_savepoints(self):
-        return self.uses_savepoints
-
-    @cached_property
-    def can_share_in_memory_db(self):
-        return (
-            sys.version_info[:2] >= (3, 4) and
-            Database.__name__ == 'sqlite3.dbapi2' and
-            Database.sqlite_version_info >= (3, 7, 13)
-        )
-
-    @cached_property
-    def supports_stddev(self):
-        """Confirm support for STDDEV and related stats functions
-
-        SQLite supports STDDEV as an extension package; so
-        connection.ops.check_aggregate_support() can't unilaterally
-        rule out support for STDDEV. We need to manually check
-        whether the call works.
-        """
-        with self.connection.cursor() as cursor:
-            cursor.execute('CREATE TABLE STDDEV_TEST (X INT)')
-            try:
-                cursor.execute('SELECT STDDEV(*) FROM STDDEV_TEST')
-                has_support = True
-            except utils.DatabaseError:
-                has_support = False
-            cursor.execute('DROP TABLE STDDEV_TEST')
-        return has_support
-
-    @cached_property
-    def has_zoneinfo_database(self):
-        return pytz is not None
-
-
-class DatabaseOperations(BaseDatabaseOperations):
-    def bulk_batch_size(self, fields, objs):
-        """
-        SQLite has a compile-time default (SQLITE_LIMIT_VARIABLE_NUMBER) of
-        999 variables per query.
-
-        If there is just single field to insert, then we can hit another
-        limit, SQLITE_MAX_COMPOUND_SELECT which defaults to 500.
-        """
-        limit = 999 if len(fields) > 1 else 500
-        return (limit // len(fields)) if len(fields) > 0 else len(objs)
-
-    def check_aggregate_support(self, aggregate):
-        bad_fields = (fields.DateField, fields.DateTimeField, fields.TimeField)
-        bad_aggregates = (aggregates.Sum, aggregates.Avg,
-                          aggregates.Variance, aggregates.StdDev)
-        if aggregate.refs_field(bad_aggregates, bad_fields):
-            raise NotImplementedError(
-                'You cannot use Sum, Avg, StdDev and Variance aggregations '
-                'on date/time fields in sqlite3 '
-                'since date/time is saved as text.')
-
-    def date_extract_sql(self, lookup_type, field_name):
-        # sqlite doesn't support extract, so we fake it with the user-defined
-        # function django_date_extract that's registered in connect(). Note that
-        # single quotes are used because this is a string (and could otherwise
-        # cause a collision with a field name).
-        return "django_date_extract('%s', %s)" % (lookup_type.lower(), field_name)
-
-    def date_interval_sql(self, timedelta):
-        return "'%s'" % duration_string(timedelta), []
-
-    def format_for_duration_arithmetic(self, sql):
-        """Do nothing here, we will handle it in the custom function."""
-        return sql
-
-    def date_trunc_sql(self, lookup_type, field_name):
-        # sqlite doesn't support DATE_TRUNC, so we fake it with a user-defined
-        # function django_date_trunc that's registered in connect(). Note that
-        # single quotes are used because this is a string (and could otherwise
-        # cause a collision with a field name).
-        return "django_date_trunc('%s', %s)" % (lookup_type.lower(), field_name)
-
-    def datetime_extract_sql(self, lookup_type, field_name, tzname):
-        # Same comment as in date_extract_sql.
-        if settings.USE_TZ:
-            if pytz is None:
-                from django.core.exceptions import ImproperlyConfigured
-                raise ImproperlyConfigured("This query requires pytz, "
-                                           "but it isn't installed.")
-        return "django_datetime_extract('%s', %s, %%s)" % (
-            lookup_type.lower(), field_name), [tzname]
-
-    def datetime_trunc_sql(self, lookup_type, field_name, tzname):
-        # Same comment as in date_trunc_sql.
-        if settings.USE_TZ:
-            if pytz is None:
-                from django.core.exceptions import ImproperlyConfigured
-                raise ImproperlyConfigured("This query requires pytz, "
-                                           "but it isn't installed.")
-        return "django_datetime_trunc('%s', %s, %%s)" % (
-            lookup_type.lower(), field_name), [tzname]
-
-    def drop_foreignkey_sql(self):
-        return ""
-
-    def pk_default_value(self):
-        return "NULL"
-
-    def quote_name(self, name):
-        if name.startswith('"') and name.endswith('"'):
-            return name  # Quoting once is enough.
-        return '"%s"' % name
-
-    def no_limit_value(self):
-        return -1
-
-    def sql_flush(self, style, tables, sequences, allow_cascade=False):
-        # NB: The generated SQL below is specific to SQLite
-        # Note: The DELETE FROM... SQL generated below works for SQLite databases
-        # because constraints don't exist
-        sql = ['%s %s %s;' % (
-            style.SQL_KEYWORD('DELETE'),
-            style.SQL_KEYWORD('FROM'),
-            style.SQL_FIELD(self.quote_name(table))
-        ) for table in tables]
-        # Note: No requirement for reset of auto-incremented indices (cf. other
-        # sql_flush() implementations). Just return SQL at this point
-        return sql
-
-    def value_to_db_datetime(self, value):
-        if value is None:
-            return None
-
-        # SQLite doesn't support tz-aware datetimes
-        if timezone.is_aware(value):
-            if settings.USE_TZ:
-                value = value.astimezone(timezone.utc).replace(tzinfo=None)
-            else:
-                raise ValueError("SQLite backend does not support timezone-aware datetimes when USE_TZ is False.")
-
-        return six.text_type(value)
-
-    def value_to_db_time(self, value):
-        if value is None:
-            return None
-
-        # SQLite doesn't support tz-aware datetimes
-        if timezone.is_aware(value):
-            raise ValueError("SQLite backend does not support timezone-aware times.")
-
-        return six.text_type(value)
-
-    def get_db_converters(self, expression):
-        converters = super(DatabaseOperations, self).get_db_converters(expression)
-        internal_type = expression.output_field.get_internal_type()
-        if internal_type == 'DateTimeField':
-            converters.append(self.convert_datetimefield_value)
-        elif internal_type == 'DateField':
-            converters.append(self.convert_datefield_value)
-        elif internal_type == 'TimeField':
-            converters.append(self.convert_timefield_value)
-        elif internal_type == 'DecimalField':
-            converters.append(self.convert_decimalfield_value)
-        elif internal_type == 'UUIDField':
-            converters.append(self.convert_uuidfield_value)
-        return converters
-
-    def convert_decimalfield_value(self, value, expression, context):
-        return backend_utils.typecast_decimal(expression.output_field.format_number(value))
-
-    def convert_datefield_value(self, value, expression, context):
-        if value is not None and not isinstance(value, datetime.date):
-            value = parse_date(value)
-        return value
-
-    def convert_datetimefield_value(self, value, expression, context):
-        if value is not None and not isinstance(value, datetime.datetime):
-            value = parse_datetime_with_timezone_support(value)
-        return value
-
-    def convert_timefield_value(self, value, expression, context):
-        if value is not None and not isinstance(value, datetime.time):
-            value = parse_time(value)
-        return value
-
-    def convert_uuidfield_value(self, value, expression, context):
-        if value is not None:
-            value = uuid.UUID(value)
-        return value
-
-    def bulk_insert_sql(self, fields, num_values):
-        res = []
-        res.append("SELECT %s" % ", ".join(
-            "%%s AS %s" % self.quote_name(f.column) for f in fields
-        ))
-        res.extend(["UNION ALL SELECT %s" % ", ".join(["%s"] * len(fields))] * (num_values - 1))
-        return " ".join(res)
-
-    def combine_expression(self, connector, sub_expressions):
-        # SQLite doesn't have a power function, so we fake it with a
-        # user-defined function django_power that's registered in connect().
-        if connector == '^':
-            return 'django_power(%s)' % ','.join(sub_expressions)
-        return super(DatabaseOperations, self).combine_expression(connector, sub_expressions)
-
-    def combine_duration_expression(self, connector, sub_expressions):
-        if connector not in ['+', '-']:
-            raise utils.DatabaseError('Invalid connector for timedelta: %s.' % connector)
-        fn_params = ["'%s'" % connector] + sub_expressions
-        if len(fn_params) > 3:
-            raise ValueError('Too many params for timedelta operations.')
-        return "django_format_dtdelta(%s)" % ', '.join(fn_params)
-
-    def integer_field_range(self, internal_type):
-        # SQLite doesn't enforce any integer constraints
-        return (None, None)
-
-
 class DatabaseWrapper(BaseDatabaseWrapper):
     vendor = 'sqlite'
     # SQLite doesn't actually support most of these types, but it "does the right

django/db/backends/sqlite3/client.py

@@ -1,6 +1,6 @@
 import subprocess
 
-from django.db.backends import BaseDatabaseClient
+from django.db.backends.base.client import BaseDatabaseClient
 
 
 class DatabaseClient(BaseDatabaseClient):

django/db/backends/sqlite3/creation.py

@@ -2,7 +2,7 @@ import os
 import sys
 
 from django.core.exceptions import ImproperlyConfigured
-from django.db.backends.creation import BaseDatabaseCreation
+from django.db.backends.base.creation import BaseDatabaseCreation
 from django.utils.six.moves import input
 
 

django/db/backends/sqlite3/features.py

@@ -0,0 +1,79 @@
+from __future__ import unicode_literals
+
+import sys
+
+from django.db import utils
+from django.db.backends.base.features import BaseDatabaseFeatures
+from django.utils.functional import cached_property
+
+from .base import Database
+
+try:
+    import pytz
+except ImportError:
+    pytz = None
+
+
+class DatabaseFeatures(BaseDatabaseFeatures):
+    # SQLite cannot handle us only partially reading from a cursor's result set
+    # and then writing the same rows to the database in another cursor. This
+    # setting ensures we always read result sets fully into memory all in one
+    # go.
+    can_use_chunked_reads = False
+    test_db_allows_multiple_connections = False
+    supports_unspecified_pk = True
+    supports_timezones = False
+    supports_1000_query_parameters = False
+    supports_mixed_date_datetime_comparisons = False
+    has_bulk_insert = True
+    can_combine_inserts_with_and_without_auto_increment_pk = False
+    supports_foreign_keys = False
+    supports_column_check_constraints = False
+    autocommits_when_autocommit_is_off = True
+    can_introspect_decimal_field = False
+    can_introspect_positive_integer_field = True
+    can_introspect_small_integer_field = True
+    supports_transactions = True
+    atomic_transactions = False
+    can_rollback_ddl = True
+    supports_paramstyle_pyformat = False
+    supports_sequence_reset = False
+
+    @cached_property
+    def uses_savepoints(self):
+        return Database.sqlite_version_info >= (3, 6, 8)
+
+    @cached_property
+    def can_release_savepoints(self):
+        return self.uses_savepoints
+
+    @cached_property
+    def can_share_in_memory_db(self):
+        return (
+            sys.version_info[:2] >= (3, 4) and
+            Database.__name__ == 'sqlite3.dbapi2' and
+            Database.sqlite_version_info >= (3, 7, 13)
+        )
+
+    @cached_property
+    def supports_stddev(self):
+        """Confirm support for STDDEV and related stats functions
+
+        SQLite supports STDDEV as an extension package; so
+        connection.ops.check_aggregate_support() can't unilaterally
+        rule out support for STDDEV. We need to manually check
+        whether the call works.
+        """
+        with self.connection.cursor() as cursor:
+            cursor.execute('CREATE TABLE STDDEV_TEST (X INT)')
+            try:
+                cursor.execute('SELECT STDDEV(*) FROM STDDEV_TEST')
+                has_support = True
+            except utils.DatabaseError:
+                has_support = False
+            cursor.execute('DROP TABLE STDDEV_TEST')
+        return has_support
+
+    @cached_property
+    def has_zoneinfo_database(self):
+        return pytz is not None

django/db/backends/sqlite3/introspection.py

@@ -1,6 +1,8 @@
 import re
 
-from django.db.backends import BaseDatabaseIntrospection, FieldInfo, TableInfo
+from django.db.backends.base.introspection import (
+    BaseDatabaseIntrospection, FieldInfo, TableInfo,
+)
 
 
 field_size_re = re.compile(r'^\s*(?:var)?char\s*\(\s*(\d+)\s*\)\s*$')

django/db/backends/sqlite3/operations.py

@@ -0,0 +1,198 @@
+from __future__ import unicode_literals
+
+import datetime
+import uuid
+
+from django.conf import settings
+from django.core.exceptions import ImproperlyConfigured
+from django.db import utils
+from django.db.backends import utils as backend_utils
+from django.db.backends.base.operations import BaseDatabaseOperations
+from django.db.models import fields, aggregates
+from django.utils.dateparse import parse_date, parse_time
+from django.utils.duration import duration_string
+from django.utils import six, timezone
+
+from .utils import parse_datetime_with_timezone_support
+
+try:
+    import pytz
+except ImportError:
+    pytz = None
+
+
+class DatabaseOperations(BaseDatabaseOperations):
+    def bulk_batch_size(self, fields, objs):
+        """
+        SQLite has a compile-time default (SQLITE_LIMIT_VARIABLE_NUMBER) of
+        999 variables per query.
+
+        If there is just single field to insert, then we can hit another
+        limit, SQLITE_MAX_COMPOUND_SELECT which defaults to 500.
+        """
+        limit = 999 if len(fields) > 1 else 500
+        return (limit // len(fields)) if len(fields) > 0 else len(objs)
+
+    def check_aggregate_support(self, aggregate):
+        bad_fields = (fields.DateField, fields.DateTimeField, fields.TimeField)
+        bad_aggregates = (aggregates.Sum, aggregates.Avg,
+                          aggregates.Variance, aggregates.StdDev)
+        if aggregate.refs_field(bad_aggregates, bad_fields):
+            raise NotImplementedError(
+                'You cannot use Sum, Avg, StdDev and Variance aggregations '
+                'on date/time fields in sqlite3 '
+                'since date/time is saved as text.')
+
+    def date_extract_sql(self, lookup_type, field_name):
+        # sqlite doesn't support extract, so we fake it with the user-defined
+        # function django_date_extract that's registered in connect(). Note that
+        # single quotes are used because this is a string (and could otherwise
+        # cause a collision with a field name).
+        return "django_date_extract('%s', %s)" % (lookup_type.lower(), field_name)
+
+    def date_interval_sql(self, timedelta):
+        return "'%s'" % duration_string(timedelta), []
+
+    def format_for_duration_arithmetic(self, sql):
+        """Do nothing here, we will handle it in the custom function."""
+        return sql
+
+    def date_trunc_sql(self, lookup_type, field_name):
+        # sqlite doesn't support DATE_TRUNC, so we fake it with a user-defined
+        # function django_date_trunc that's registered in connect(). Note that
+        # single quotes are used because this is a string (and could otherwise
+        # cause a collision with a field name).
+        return "django_date_trunc('%s', %s)" % (lookup_type.lower(), field_name)
+
+    def datetime_extract_sql(self, lookup_type, field_name, tzname):
+        # Same comment as in date_extract_sql.
+        if settings.USE_TZ:
+            if pytz is None:
+                raise ImproperlyConfigured("This query requires pytz, "
+                                           "but it isn't installed.")
+        return "django_datetime_extract('%s', %s, %%s)" % (
+            lookup_type.lower(), field_name), [tzname]
+
+    def datetime_trunc_sql(self, lookup_type, field_name, tzname):
+        # Same comment as in date_trunc_sql.
+        if settings.USE_TZ:
+            if pytz is None:
+                raise ImproperlyConfigured("This query requires pytz, "
+                                           "but it isn't installed.")
+        return "django_datetime_trunc('%s', %s, %%s)" % (
+            lookup_type.lower(), field_name), [tzname]
+
+    def drop_foreignkey_sql(self):
+        return ""
+
+    def pk_default_value(self):
+        return "NULL"
+
+    def quote_name(self, name):
+        if name.startswith('"') and name.endswith('"'):
+            return name  # Quoting once is enough.
+        return '"%s"' % name
+
+    def no_limit_value(self):
+        return -1
+
+    def sql_flush(self, style, tables, sequences, allow_cascade=False):
+        # NB: The generated SQL below is specific to SQLite
+        # Note: The DELETE FROM... SQL generated below works for SQLite databases
+        # because constraints don't exist
+        sql = ['%s %s %s;' % (
+            style.SQL_KEYWORD('DELETE'),
+            style.SQL_KEYWORD('FROM'),
+            style.SQL_FIELD(self.quote_name(table))
+        ) for table in tables]
+        # Note: No requirement for reset of auto-incremented indices (cf. other
+        # sql_flush() implementations). Just return SQL at this point
+        return sql
+
+    def value_to_db_datetime(self, value):
+        if value is None:
+            return None
+
+        # SQLite doesn't support tz-aware datetimes
+        if timezone.is_aware(value):
+            if settings.USE_TZ:
+                value = value.astimezone(timezone.utc).replace(tzinfo=None)
+            else:
+                raise ValueError("SQLite backend does not support timezone-aware datetimes when USE_TZ is False.")
+
+        return six.text_type(value)
+
+    def value_to_db_time(self, value):
+        if value is None:
+            return None
+
+        # SQLite doesn't support tz-aware datetimes
+        if timezone.is_aware(value):
+            raise ValueError("SQLite backend does not support timezone-aware times.")
+
+        return six.text_type(value)
+
+    def get_db_converters(self, expression):
+        converters = super(DatabaseOperations, self).get_db_converters(expression)
+        internal_type = expression.output_field.get_internal_type()
+        if internal_type == 'DateTimeField':
+            converters.append(self.convert_datetimefield_value)
+        elif internal_type == 'DateField':
+            converters.append(self.convert_datefield_value)
+        elif internal_type == 'TimeField':
+            converters.append(self.convert_timefield_value)
+        elif internal_type == 'DecimalField':
+            converters.append(self.convert_decimalfield_value)
+        elif internal_type == 'UUIDField':
+            converters.append(self.convert_uuidfield_value)
+        return converters
+
+    def convert_decimalfield_value(self, value, expression, context):
+        return backend_utils.typecast_decimal(expression.output_field.format_number(value))
+
+    def convert_datefield_value(self, value, expression, context):
+        if value is not None and not isinstance(value, datetime.date):
+            value = parse_date(value)
+        return value
+
+    def convert_datetimefield_value(self, value, expression, context):
+        if value is not None and not isinstance(value, datetime.datetime):
+            value = parse_datetime_with_timezone_support(value)
+        return value
+
+    def convert_timefield_value(self, value, expression, context):
+        if value is not None and not isinstance(value, datetime.time):
+            value = parse_time(value)
+        return value
+
+    def convert_uuidfield_value(self, value, expression, context):
+        if value is not None:
+            value = uuid.UUID(value)
+        return value
+
+    def bulk_insert_sql(self, fields, num_values):
+        res = []
+        res.append("SELECT %s" % ", ".join(
+            "%%s AS %s" % self.quote_name(f.column) for f in fields
+        ))
+        res.extend(["UNION ALL SELECT %s" % ", ".join(["%s"] * len(fields))] * (num_values - 1))
+        return " ".join(res)
+
+    def combine_expression(self, connector, sub_expressions):
+        # SQLite doesn't have a power function, so we fake it with a
+        # user-defined function django_power that's registered in connect().
+        if connector == '^':
+            return 'django_power(%s)' % ','.join(sub_expressions)
+        return super(DatabaseOperations, self).combine_expression(connector, sub_expressions)
+
+    def combine_duration_expression(self, connector, sub_expressions):
+        if connector not in ['+', '-']:
+            raise utils.DatabaseError('Invalid connector for timedelta: %s.' % connector)
+        fn_params = ["'%s'" % connector] + sub_expressions
+        if len(fn_params) > 3:
+            raise ValueError('Too many params for timedelta operations.')
+        return "django_format_dtdelta(%s)" % ', '.join(fn_params)
+
+    def integer_field_range(self, internal_type):
+        # SQLite doesn't enforce any integer constraints
+        return (None, None)

django/db/backends/sqlite3/schema.py

@@ -1,10 +1,13 @@
 import codecs
 import copy
 from decimal import Decimal
-from django.utils import six
+
 from django.apps.registry import Apps
-from django.db.backends.schema import BaseDatabaseSchemaEditor
+from django.db.backends.base.schema import BaseDatabaseSchemaEditor
 from django.db.models.fields.related import ManyToManyField
+from django.utils import six
+
+import _sqlite3
 
 
 class DatabaseSchemaEditor(BaseDatabaseSchemaEditor):
@@ -13,8 +16,6 @@ class DatabaseSchemaEditor(BaseDatabaseSchemaEditor):
     sql_create_inline_fk = "REFERENCES %(to_table)s (%(to_column)s)"
 
     def quote_value(self, value):
-        # Inner import to allow nice failure for backend if not present
-        import _sqlite3
         try:
             value = _sqlite3.adapt(value)
         except _sqlite3.ProgrammingError:

django/db/backends/sqlite3/utils.py

@@ -0,0 +1,11 @@
+from django.conf import settings
+from django.utils import timezone
+from django.utils.dateparse import parse_datetime
+
+
+def parse_datetime_with_timezone_support(value):
+    dt = parse_datetime(value)
+    # Confirm that dt is naive before overwriting its tzinfo.
+    if dt is not None and settings.USE_TZ and timezone.is_naive(dt):
+        dt = dt.replace(tzinfo=timezone.utc)
+    return dt

docs/ref/migration-operations.txt

@@ -272,7 +272,7 @@ if supplied) should be callable objects that accept two arguments; the first is
 an instance of ``django.apps.registry.Apps`` containing historical models that
 match the operation's place in the project history, and the second is an
 instance of :class:`SchemaEditor
-<django.db.backends.schema.BaseDatabaseSchemaEditor>`.
+<django.db.backends.base.schema.BaseDatabaseSchemaEditor>`.
 
 The optional ``hints`` argument will be passed as ``**hints`` to the
 :meth:`allow_migrate` method of database routers to assist them in making a

docs/ref/schema-editor.txt

@@ -2,7 +2,7 @@
 ``SchemaEditor``
 ================
 
-.. module:: django.db.backends.schema
+.. module:: django.db.backends.base.schema
 
 .. class:: BaseDatabaseSchemaEditor
 

docs/releases/1.8.txt

@@ -942,6 +942,19 @@ Database backend API
 The following changes to the database backend API are documented to assist
 those writing third-party backends in updating their code:
 
+* ``BaseDatabaseXXX`` classes have been moved to ``django.db.backends.base``.
+  Please import them from the new locations::
+
+    from django.db.backends.base.base import BaseDatabaseWrapper
+    from django.db.backends.base.client import BaseDatabaseClient
+    from django.db.backends.base.creation import BaseDatabaseCreation
+    from django.db.backends.base.features import BaseDatabaseFeatures
+    from django.db.backends.base.introspection import BaseDatabaseIntrospection
+    from django.db.backends.base.introspection import FieldInfo, TableInfo
+    from django.db.backends.base.operations import BaseDatabaseOperations
+    from django.db.backends.base.schema import BaseDatabaseSchemaEditor
+    from django.db.backends.base.validation import BaseDatabaseValidation
+
 * The ``data_types``, ``data_types_suffix``, and
   ``data_type_check_constraints`` attributes have moved from the
   ``DatabaseCreation`` class to ``DatabaseWrapper``.

tests/backends/tests.py

@@ -15,7 +15,7 @@ from django.core.exceptions import ImproperlyConfigured
 from django.core.management.color import no_style
 from django.db import (connection, connections, DEFAULT_DB_ALIAS,
     DatabaseError, IntegrityError, reset_queries, transaction)
-from django.db.backends import BaseDatabaseWrapper
+from django.db.backends.base.base import BaseDatabaseWrapper
 from django.db.backends.signals import connection_created
 from django.db.backends.postgresql_psycopg2 import version as pg_version
 from django.db.backends.utils import format_number, CursorWrapper