django/tests/backends/base/test_base.py

from unittest.mock import MagicMock, patch

from django.db import DEFAULT_DB_ALIAS, connection, connections
from django.db.backends.base.base import BaseDatabaseWrapper
from django.test import SimpleTestCase, TestCase, skipUnlessDBFeature

from ..models import Square


class DatabaseWrapperTests(SimpleTestCase):

    def test_repr(self):
        conn = connections[DEFAULT_DB_ALIAS]
        self.assertEqual(
            repr(conn),
            f"<DatabaseWrapper vendor={connection.vendor!r} alias='default'>",
        )

    def test_initialization_class_attributes(self):
        """
        The "initialization" class attributes like client_class and
        creation_class should be set on the class and reflected in the
        corresponding instance attributes of the instantiated backend.
        """
        conn = connections[DEFAULT_DB_ALIAS]
        conn_class = type(conn)
        attr_names = [
            ('client_class', 'client'),
            ('creation_class', 'creation'),
            ('features_class', 'features'),
            ('introspection_class', 'introspection'),
            ('ops_class', 'ops'),
            ('validation_class', 'validation'),
        ]
        for class_attr_name, instance_attr_name in attr_names:
            class_attr_value = getattr(conn_class, class_attr_name)
            self.assertIsNotNone(class_attr_value)
            instance_attr_value = getattr(conn, instance_attr_name)
            self.assertIsInstance(instance_attr_value, class_attr_value)

    def test_initialization_display_name(self):
        self.assertEqual(BaseDatabaseWrapper.display_name, 'unknown')
        self.assertNotEqual(connection.display_name, 'unknown')


class ExecuteWrapperTests(TestCase):

    @staticmethod
    def call_execute(connection, params=None):
        ret_val = '1' if params is None else '%s'
        sql = 'SELECT ' + ret_val + connection.features.bare_select_suffix
        with connection.cursor() as cursor:
            cursor.execute(sql, params)

    def call_executemany(self, connection, params=None):
        # executemany() must use an update query. Make sure it does nothing
        # by putting a false condition in the WHERE clause.
        sql = 'DELETE FROM {} WHERE 0=1 AND 0=%s'.format(Square._meta.db_table)
        if params is None:
            params = [(i,) for i in range(3)]
        with connection.cursor() as cursor:
            cursor.executemany(sql, params)

    @staticmethod
    def mock_wrapper():
        return MagicMock(side_effect=lambda execute, *args: execute(*args))

    def test_wrapper_invoked(self):
        wrapper = self.mock_wrapper()
        with connection.execute_wrapper(wrapper):
            self.call_execute(connection)
        self.assertTrue(wrapper.called)
        (_, sql, params, many, context), _ = wrapper.call_args
        self.assertIn('SELECT', sql)
        self.assertIsNone(params)
        self.assertIs(many, False)
        self.assertEqual(context['connection'], connection)

    def test_wrapper_invoked_many(self):
        wrapper = self.mock_wrapper()
        with connection.execute_wrapper(wrapper):
            self.call_executemany(connection)
        self.assertTrue(wrapper.called)
        (_, sql, param_list, many, context), _ = wrapper.call_args
        self.assertIn('DELETE', sql)
        self.assertIsInstance(param_list, (list, tuple))
        self.assertIs(many, True)
        self.assertEqual(context['connection'], connection)

    def test_database_queried(self):
        wrapper = self.mock_wrapper()
        with connection.execute_wrapper(wrapper):
            with connection.cursor() as cursor:
                sql = 'SELECT 17' + connection.features.bare_select_suffix
                cursor.execute(sql)
                seventeen = cursor.fetchall()
                self.assertEqual(list(seventeen), [(17,)])
            self.call_executemany(connection)

    def test_nested_wrapper_invoked(self):
        outer_wrapper = self.mock_wrapper()
        inner_wrapper = self.mock_wrapper()
        with connection.execute_wrapper(outer_wrapper), connection.execute_wrapper(inner_wrapper):
            self.call_execute(connection)
            self.assertEqual(inner_wrapper.call_count, 1)
            self.call_executemany(connection)
            self.assertEqual(inner_wrapper.call_count, 2)

    def test_outer_wrapper_blocks(self):
        def blocker(*args):
            pass
        wrapper = self.mock_wrapper()
        c = connection  # This alias shortens the next line.
        with c.execute_wrapper(wrapper), c.execute_wrapper(blocker), c.execute_wrapper(wrapper):
            with c.cursor() as cursor:
                cursor.execute("The database never sees this")
                self.assertEqual(wrapper.call_count, 1)
                cursor.executemany("The database never sees this %s", [("either",)])
                self.assertEqual(wrapper.call_count, 2)

    def test_wrapper_gets_sql(self):
        wrapper = self.mock_wrapper()
        sql = "SELECT 'aloha'" + connection.features.bare_select_suffix
        with connection.execute_wrapper(wrapper), connection.cursor() as cursor:
            cursor.execute(sql)
        (_, reported_sql, _, _, _), _ = wrapper.call_args
        self.assertEqual(reported_sql, sql)

    def test_wrapper_connection_specific(self):
        wrapper = self.mock_wrapper()
        with connections['other'].execute_wrapper(wrapper):
            self.assertEqual(connections['other'].execute_wrappers, [wrapper])
            self.call_execute(connection)
        self.assertFalse(wrapper.called)
        self.assertEqual(connection.execute_wrappers, [])
        self.assertEqual(connections['other'].execute_wrappers, [])


class ConnectionHealthChecksTests(SimpleTestCase):
    databases = {'default'}

    def setUp(self):
        # All test cases here need newly configured and created connections.
        # Use the default db connection for convenience.
        connection.close()
        self.addCleanup(connection.close)

    def patch_settings_dict(self, conn_health_checks):
        self.settings_dict_patcher = patch.dict(connection.settings_dict, {
            **connection.settings_dict,
            'CONN_MAX_AGE': None,
            'CONN_HEALTH_CHECKS': conn_health_checks,
        })
        self.settings_dict_patcher.start()
        self.addCleanup(self.settings_dict_patcher.stop)

    def run_query(self):
        with connection.cursor() as cursor:
            cursor.execute('SELECT 42' + connection.features.bare_select_suffix)

    @skipUnlessDBFeature('test_db_allows_multiple_connections')
    def test_health_checks_enabled(self):
        self.patch_settings_dict(conn_health_checks=True)
        self.assertIsNone(connection.connection)
        # Newly created connections are considered healthy without performing
        # the health check.
        with patch.object(connection, 'is_usable', side_effect=AssertionError):
            self.run_query()

        old_connection = connection.connection
        # Simulate request_finished.
        connection.close_if_unusable_or_obsolete()
        self.assertIs(old_connection, connection.connection)

        # Simulate connection health check failing.
        with patch.object(connection, 'is_usable', return_value=False) as mocked_is_usable:
            self.run_query()
            new_connection = connection.connection
            # A new connection is established.
            self.assertIsNot(new_connection, old_connection)
            # Only one health check per "request" is performed, so the next
            # query will carry on even if the health check fails. Next query
            # succeeds because the real connection is healthy and only the
            # health check failure is mocked.
            self.run_query()
            self.assertIs(new_connection, connection.connection)
        self.assertEqual(mocked_is_usable.call_count, 1)

        # Simulate request_finished.
        connection.close_if_unusable_or_obsolete()
        # The underlying connection is being reused further with health checks
        # succeeding.
        self.run_query()
        self.run_query()
        self.assertIs(new_connection, connection.connection)

    @skipUnlessDBFeature('test_db_allows_multiple_connections')
    def test_health_checks_enabled_errors_occurred(self):
        self.patch_settings_dict(conn_health_checks=True)
        self.assertIsNone(connection.connection)
        # Newly created connections are considered healthy without performing
        # the health check.
        with patch.object(connection, 'is_usable', side_effect=AssertionError):
            self.run_query()

        old_connection = connection.connection
        # Simulate errors_occurred.
        connection.errors_occurred = True
        # Simulate request_started (the connection is healthy).
        connection.close_if_unusable_or_obsolete()
        # Persistent connections are enabled.
        self.assertIs(old_connection, connection.connection)
        # No additional health checks after the one in
        # close_if_unusable_or_obsolete() are executed during this "request"
        # when running queries.
        with patch.object(connection, 'is_usable', side_effect=AssertionError):
            self.run_query()

    @skipUnlessDBFeature('test_db_allows_multiple_connections')
    def test_health_checks_disabled(self):
        self.patch_settings_dict(conn_health_checks=False)
        self.assertIsNone(connection.connection)
        # Newly created connections are considered healthy without performing
        # the health check.
        with patch.object(connection, 'is_usable', side_effect=AssertionError):
            self.run_query()

        old_connection = connection.connection
        # Simulate request_finished.
        connection.close_if_unusable_or_obsolete()
        # Persistent connections are enabled (connection is not).
        self.assertIs(old_connection, connection.connection)
        # Health checks are not performed.
        with patch.object(connection, 'is_usable', side_effect=AssertionError):
            self.run_query()
            # Health check wasn't performed and the connection is unchanged.
            self.assertIs(old_connection, connection.connection)
            self.run_query()
            # The connection is unchanged after the next query either during
            # the current "request".
            self.assertIs(old_connection, connection.connection)

    @skipUnlessDBFeature('test_db_allows_multiple_connections')
    def test_set_autocommit_health_checks_enabled(self):
        self.patch_settings_dict(conn_health_checks=True)
        self.assertIsNone(connection.connection)
        # Newly created connections are considered healthy without performing
        # the health check.
        with patch.object(connection, 'is_usable', side_effect=AssertionError):
            # Simulate outermost atomic block: changing autocommit for
            # a connection.
            connection.set_autocommit(False)
            self.run_query()
            connection.commit()
            connection.set_autocommit(True)

        old_connection = connection.connection
        # Simulate request_finished.
        connection.close_if_unusable_or_obsolete()
        # Persistent connections are enabled.
        self.assertIs(old_connection, connection.connection)

        # Simulate connection health check failing.
        with patch.object(connection, 'is_usable', return_value=False) as mocked_is_usable:
            # Simulate outermost atomic block: changing autocommit for
            # a connection.
            connection.set_autocommit(False)
            new_connection = connection.connection
            self.assertIsNot(new_connection, old_connection)
            # Only one health check per "request" is performed, so a query will
            # carry on even if the health check fails. This query succeeds
            # because the real connection is healthy and only the health check
            # failure is mocked.
            self.run_query()
            connection.commit()
            connection.set_autocommit(True)
            # The connection is unchanged.
            self.assertIs(new_connection, connection.connection)
        self.assertEqual(mocked_is_usable.call_count, 1)

        # Simulate request_finished.
        connection.close_if_unusable_or_obsolete()
        # The underlying connection is being reused further with health checks
        # succeeding.
        connection.set_autocommit(False)
        self.run_query()
        connection.commit()
        connection.set_autocommit(True)
        self.assertIs(new_connection, connection.connection)