Linked GIS functions docs to corresponding MySQL docs.

docs/ref/contrib/gis/functions.txt

@@ -38,8 +38,9 @@ Measurement         Relationships              Operations              Editors
 
 .. class:: Area(expression, **extra)
 
-*Availability*: MySQL, Oracle,
-`PostGIS <https://postgis.net/docs/ST_Area.html>`__, SpatiaLite
+*Availability*: `MySQL
+<https://dev.mysql.com/doc/refman/en/gis-polygon-property-functions.html#function_area>`__,
+Oracle, `PostGIS <https://postgis.net/docs/ST_Area.html>`__, SpatiaLite
 
 Accepts a single geographic field or expression and returns the area of the
 field as an :class:`~django.contrib.gis.measure.Area` measure.
@@ -52,8 +53,9 @@ geographic SRSes.
 
 .. class:: AsGeoJSON(expression, bbox=False, crs=False, precision=8, **extra)
 
-*Availability*: MySQL (≥ 5.7.5), `PostGIS
-<https://postgis.net/docs/ST_AsGeoJSON.html>`__, SpatiaLite
+*Availability*: `MySQL
+<https://dev.mysql.com/doc/refman/en/spatial-geojson-functions.html#function_st-asgeojson>`__ (≥ 5.7.5),
+`PostGIS <https://postgis.net/docs/ST_AsGeoJSON.html>`__, SpatiaLite
 
 Accepts a single geographic field or expression and returns a `GeoJSON
 <http://geojson.org/>`_ representation of the geometry. Note that the result is
@@ -198,8 +200,9 @@ The ``num_seg`` parameter is used only on PostGIS.
 
 .. class:: Centroid(expression, **extra)
 
-*Availability*: MySQL, `PostGIS <https://postgis.net/docs/ST_Centroid.html>`__,
-Oracle, SpatiaLite
+*Availability*: `MySQL
+<https://dev.mysql.com/doc/refman/en/gis-polygon-property-functions.html#function_st-centroid>`__,
+`PostGIS <https://postgis.net/docs/ST_Centroid.html>`__, Oracle, SpatiaLite
 
 Accepts a single geographic field or expression and returns the ``centroid``
 value of the geometry.
@@ -209,8 +212,9 @@ value of the geometry.
 
 .. class:: Difference(expr1, expr2, **extra)
 
-*Availability*: MySQL, `PostGIS
-<https://postgis.net/docs/ST_Difference.html>`__, Oracle, SpatiaLite
+*Availability*: `MySQL
+<https://dev.mysql.com/doc/refman/en/spatial-operator-functions.html#function_st-difference>`__,
+`PostGIS <https://postgis.net/docs/ST_Difference.html>`__, Oracle, SpatiaLite
 
 Accepts two geographic fields or expressions and returns the geometric
 difference, that is the part of geometry A that does not intersect with
@@ -221,8 +225,9 @@ geometry B.
 
 .. class:: Distance(expr1, expr2, spheroid=None, **extra)
 
-*Availability*: MySQL, `PostGIS <https://postgis.net/docs/ST_Distance.html>`__,
-Oracle, SpatiaLite
+*Availability*: `MySQL
+<https://dev.mysql.com/doc/refman/en/spatial-relation-functions-object-shapes.html#function_st-distance>`__,
+`PostGIS <https://postgis.net/docs/ST_Distance.html>`__, Oracle, SpatiaLite
 
 Accepts two geographic fields or expressions and returns the distance between
 them, as a :class:`~django.contrib.gis.measure.Distance` object. On MySQL, a raw
@@ -266,8 +271,9 @@ queryset is calculated::
 
 .. class:: Envelope(expression, **extra)
 
-*Availability*: MySQL, `PostGIS <https://postgis.net/docs/ST_Envelope.html>`__,
-SpatiaLite
+*Availability*: `MySQL
+<https://dev.mysql.com/doc/refman/en/gis-general-property-functions.html#function_st-envelope>`__,
+`PostGIS <https://postgis.net/docs/ST_Envelope.html>`__, SpatiaLite
 
 Accepts a single geographic field or expression and returns the geometry
 representing the bounding box of the geometry.
@@ -306,8 +312,9 @@ right-hand rule.
 
 .. class:: GeoHash(expression, precision=None, **extra)
 
-*Availability*: MySQL (≥ 5.7.5), `PostGIS
-<https://postgis.net/docs/ST_GeoHash.html>`__, SpatiaLite (LWGEOM)
+*Availability*: `MySQL
+<https://dev.mysql.com/doc/refman/en/spatial-geohash-functions.html#function_st-geohash>`__ (≥ 5.7.5),
+`PostGIS <https://postgis.net/docs/ST_GeoHash.html>`__, SpatiaLite (LWGEOM)
 
 Accepts a single geographic field or expression and returns a `GeoHash`__
 representation of the geometry.
@@ -326,8 +333,9 @@ __ https://en.wikipedia.org/wiki/Geohash
 
 .. class:: Intersection(expr1, expr2, **extra)
 
-*Availability*: MySQL, `PostGIS
-<https://postgis.net/docs/ST_Intersection.html>`__, Oracle, SpatiaLite
+*Availability*: `MySQL
+<https://dev.mysql.com/doc/refman/en/spatial-operator-functions.html#function_st-intersection>`__,
+`PostGIS <https://postgis.net/docs/ST_Intersection.html>`__, Oracle, SpatiaLite
 
 Accepts two geographic fields or expressions and returns the geometric
 intersection between them.
@@ -337,8 +345,9 @@ intersection between them.
 
 .. class:: IsValid(expr)
 
-*Availability*: MySQL (≥ 5.7.5), `PostGIS
-<https://postgis.net/docs/ST_IsValid.html>`__, Oracle, SpatiaLite (LWGEOM)
+*Availability*: `MySQL
+<https://dev.mysql.com/doc/refman/en/spatial-convenience-functions.html#function_st-isvalid>`__ (≥ 5.7.5),
+`PostGIS <https://postgis.net/docs/ST_IsValid.html>`__, Oracle, SpatiaLite (LWGEOM)
 
 Accepts a geographic field or expression and tests if the value is well formed.
 Returns ``True`` if its value is a valid geometry and ``False`` otherwise.
@@ -352,8 +361,9 @@ Returns ``True`` if its value is a valid geometry and ``False`` otherwise.
 
 .. class:: Length(expression, spheroid=True, **extra)
 
-*Availability*: MySQL, Oracle, `PostGIS
-<https://postgis.net/docs/ST_Length.html>`__, SpatiaLite
+*Availability*: `MySQL
+<https://dev.mysql.com/doc/refman/en/gis-linestring-property-functions.html#function_st-length>`__,
+Oracle, `PostGIS <https://postgis.net/docs/ST_Length.html>`__, SpatiaLite
 
 Accepts a single geographic linestring or multilinestring field or expression
 and returns its length as a :class:`~django.contrib.gis.measure.Distance`
@@ -407,8 +417,10 @@ Accepts a single geographic field or expression and returns the memory size
 
 .. class:: NumGeometries(expression, **extra)
 
-*Availability*: MySQL, `PostGIS
-<https://postgis.net/docs/ST_NumGeometries.html>`__, Oracle, SpatiaLite
+*Availability*: `MySQL
+<https://dev.mysql.com/doc/refman/en/gis-geometrycollection-property-functions.html#function_st-numgeometries>`__,
+`PostGIS <https://postgis.net/docs/ST_NumGeometries.html>`__, Oracle,
+SpatiaLite
 
 Accepts a single geographic field or expression and returns the number of
 geometries if the geometry field is a collection (e.g., a ``GEOMETRYCOLLECTION``
@@ -421,8 +433,9 @@ On MySQL, returns ``None`` for single geometries.
 
 .. class:: NumPoints(expression, **extra)
 
-*Availability*: MySQL, `PostGIS <https://postgis.net/docs/ST_NPoints.html>`__,
-Oracle, SpatiaLite
+*Availability*: `MySQL
+<https://dev.mysql.com/doc/refman/en/gis-linestring-property-functions.html#function_st-numpoints>`__,
+`PostGIS <https://postgis.net/docs/ST_NPoints.html>`__, Oracle, SpatiaLite
 
 Accepts a single geographic field or expression and returns the number of points
 in a geometry.
@@ -499,8 +512,10 @@ Number of Arguments  Description
 
 .. class:: SymDifference(expr1, expr2, **extra)
 
-*Availability*: MySQL, `PostGIS
-<https://postgis.net/docs/ST_SymDifference.html>`__, Oracle, SpatiaLite
+*Availability*: `MySQL
+<https://dev.mysql.com/doc/refman/en/spatial-operator-functions.html#function_st-symdifference>`__,
+`PostGIS <https://postgis.net/docs/ST_SymDifference.html>`__, Oracle,
+SpatiaLite
 
 Accepts two geographic fields or expressions and returns the geometric
 symmetric difference (union without the intersection) between the given
@@ -541,8 +556,9 @@ parameters.
 
 .. class:: Union(expr1, expr2, **extra)
 
-*Availability*: MySQL, `PostGIS <https://postgis.net/docs/ST_Union.html>`__,
-Oracle, SpatiaLite
+*Availability*: `MySQL
+<https://dev.mysql.com/doc/refman/en/spatial-operator-functions.html#function_st-union>`__,
+`PostGIS <https://postgis.net/docs/ST_Union.html>`__, Oracle, SpatiaLite
 
 Accepts two geographic fields or expressions and returns the union of both
 geometries.