Fixed #26455 -- Allowed filtering and repairing invalid geometries.

Added the IsValid and MakeValid database functions, and the isvalid lookup,
all for PostGIS.

Thanks Tim Graham for the review.

2 files changed, 51 insertions, 7 deletions

diff --git a/docs/ref/contrib/gis/functions.txt b/docs/ref/contrib/gis/functions.txt
index 04da9e78af..00dee42c57 100644
--- a/docs/ref/contrib/gis/functions.txt
+++ b/docs/ref/contrib/gis/functions.txt
@@ -25,13 +25,12 @@ Function's summary:
 ==================  =======================   ======================  ===================  ==================  =====================
 Measurement         Relationships             Operations              Editors              Output format       Miscellaneous
 ==================  =======================   ======================  ===================  ==================  =====================
-:class:`Area`       :class:`BoundingCircle`   :class:`Difference`     :class:`ForceRHR`    :class:`AsGeoJSON`  :class:`MemSize`
-:class:`Distance`   :class:`Centroid`         :class:`Intersection`   :class:`Reverse`     :class:`AsGML`      :class:`NumGeometries`
-:class:`Length`     :class:`Envelope`         :class:`SymDifference`  :class:`Scale`       :class:`AsKML`      :class:`NumPoints`
-:class:`Perimeter`  :class:`PointOnSurface`   :class:`Union`          :class:`SnapToGrid`  :class:`AsSVG`
-
-                                                                      :class:`Transform`   :class:`GeoHash`
-
+:class:`Area`       :class:`BoundingCircle`   :class:`Difference`     :class:`ForceRHR`    :class:`AsGeoJSON`  :class:`IsValid`
+:class:`Distance`   :class:`Centroid`         :class:`Intersection`   :class:`MakeValid`   :class:`AsGML`      :class:`MemSize`
+:class:`Length`     :class:`Envelope`         :class:`SymDifference`  :class:`Reverse`     :class:`AsKML`      :class:`NumGeometries`
+:class:`Perimeter`  :class:`PointOnSurface`   :class:`Union`          :class:`Scale`       :class:`AsSVG`      :class:`NumPoints`
+                                                                      :class:`SnapToGrid`  :class:`GeoHash`
+                                                                      :class:`Transform`
                                                                       :class:`Translate`
 ==================  =======================   ======================  ===================  ==================  =====================
 
@@ -291,6 +290,18 @@ intersection between them.
 
     MySQL support was added.
 
+``IsValid``
+===========
+
+.. class:: IsValid(expr)
+
+.. versionadded:: 1.10
+
+*Availability*: PostGIS
+
+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.
+
 ``Length``
 ==========
 
@@ -308,6 +319,20 @@ specify if the calculation should be based on a simple sphere (less
 accurate, less resource-intensive) or on a spheroid (more accurate, more
 resource-intensive) with the ``spheroid`` keyword argument.
 
+``MakeValid``
+=============
+
+.. class:: MakeValid(expr)
+
+.. versionadded:: 1.10
+
+*Availability*: PostGIS
+
+Accepts a geographic field or expression and attempts to convert the value into
+a valid geometry without losing any of the input vertices. Geometries that are
+already valid are returned without changes. Simple polygons might become a
+multipolygon and the result might be of lower dimension than the input.
+
 ``MemSize``
 ===========
 
diff --git a/docs/ref/contrib/gis/geoquerysets.txt b/docs/ref/contrib/gis/geoquerysets.txt
index ed142d72b8..6b12c07a57 100644
--- a/docs/ref/contrib/gis/geoquerysets.txt
+++ b/docs/ref/contrib/gis/geoquerysets.txt
@@ -247,6 +247,25 @@ MySQL       ``MBRIntersects(poly, geom)``
 SpatiaLite  ``Intersects(poly, geom)``
 ==========  =================================================
 
+.. fieldlookup:: isvalid
+
+``isvalid``
+-----------
+
+.. versionadded:: 1.10
+
+*Availability*: PostGIS
+
+Tests if the geometry is valid.
+
+Example::
+
+    Zipcode.objects.filter(poly__isvalid=True)
+
+PostGIS equivalent::
+
+    SELECT ... WHERE ST_IsValid(poly)
+
 .. fieldlookup:: overlaps
 
 ``overlaps``