From eece3c224e0019a30aa491a44ef66193d93f7ce8 Mon Sep 17 00:00:00 2001
From: Andrew Godwin <andrew@aeracode.org>
Date: Wed, 27 Nov 2013 13:32:12 +0000
Subject: [PATCH] PostGIS schema editor support

---
 .../contrib/gis/db/backends/postgis/base.py   |  5 ++
 .../contrib/gis/db/backends/postgis/schema.py | 87 +++++++++++++++++++
 2 files changed, 92 insertions(+)
 create mode 100644 django/contrib/gis/db/backends/postgis/schema.py

diff --git a/django/contrib/gis/db/backends/postgis/base.py b/django/contrib/gis/db/backends/postgis/base.py
index bca36e22a01..29a204ed65b 100644
--- a/django/contrib/gis/db/backends/postgis/base.py
+++ b/django/contrib/gis/db/backends/postgis/base.py
@@ -3,6 +3,7 @@ from django.db.backends.postgresql_psycopg2.base import DatabaseWrapper as Psyco
 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
 
 
 class DatabaseWrapper(Psycopg2DatabaseWrapper):
@@ -12,3 +13,7 @@ class DatabaseWrapper(Psycopg2DatabaseWrapper):
             self.creation = PostGISCreation(self)
             self.ops = PostGISOperations(self)
             self.introspection = PostGISIntrospection(self)
+
+    def schema_editor(self, *args, **kwargs):
+        "Returns a new instance of this backend's SchemaEditor"
+        return PostGISSchemaEditor(self, *args, **kwargs)
diff --git a/django/contrib/gis/db/backends/postgis/schema.py b/django/contrib/gis/db/backends/postgis/schema.py
new file mode 100644
index 00000000000..46e438acaa4
--- /dev/null
+++ b/django/contrib/gis/db/backends/postgis/schema.py
@@ -0,0 +1,87 @@
+from django.conf import settings
+from django.db.backends.postgresql_psycopg2.schema import DatabaseSchemaEditor
+from django.utils.functional import cached_property
+
+
+class PostGISSchemaEditor(DatabaseSchemaEditor):
+    geom_index_type = 'GIST'
+    geom_index_ops = 'GIST_GEOMETRY_OPS'
+    geom_index_ops_nd = 'GIST_GEOMETRY_OPS_ND'
+
+    sql_add_geometry_column = "SELECT AddGeometryColumn(%(table)s, %(column)s, %(srid)s, %(geom_type)s, %(dim)s)"
+    sql_alter_geometry_column_not_null = "ALTER TABLE %(table)s ALTER COLUMN %(column)s SET NOT NULL"
+    sql_add_spatial_index = "CREATE INDEX %(index)s ON %(table)s USING %(index_type)s (%(column)s %(ops)s)"
+
+    def geo_quote_name(self, name):
+        return self.connection.ops.geo_quote_name(name)
+
+    def create_model(self, model):
+        from django.contrib.gis.db.models.fields import GeometryField
+        # Do model creation first
+        super(PostGISSchemaEditor, self).create_model(model)
+        # Now add any spatial field SQL
+        sqls = []
+        for field in model._meta.local_fields:
+            if isinstance(field, GeometryField):
+                sqls.extend(self.spatial_field_sql(model, field))
+        for sql in sqls:
+            self.execute(sql)
+
+    def spatial_field_sql(self, model, field):
+        """
+        Takes a GeometryField and returns a list of SQL to execute to
+        create its spatial indexes.
+        """
+        output = []
+
+        if field.geography or self.connection.ops.geometry:
+            # Geography and Geometry (PostGIS 2.0+) columns are
+            # created normally.
+            pass
+        else:
+            # Geometry columns are created by the `AddGeometryColumn`
+            # stored procedure.
+            output.append(
+                self.sql_add_geometry_column % {
+                    "table": self.geo_quote_name(model._meta.db_table),
+                    "column": self.geo_quote_name(field.column),
+                    "srid": field.srid,
+                    "geom_type": self.geo_quote_name(field.geom_type),
+                    "dim": field.dim,
+                }
+            )
+            if not field.null:
+                output.append(
+                    self.sql_alter_geometry_column_not_null % {
+                        "table": self.quote_name(model._meta.db_table),
+                        "column": self.quote_name(field.column),
+                    },
+                )
+
+        if field.spatial_index:
+            # Spatial indexes created the same way for both Geometry and
+            # Geography columns.
+            # PostGIS 2.0 does not support GIST_GEOMETRY_OPS. So, on 1.5
+            # we use GIST_GEOMETRY_OPS, on 2.0 we use either "nd" ops
+            # which are fast on multidimensional cases, or just plain
+            # gist index for the 2d case.
+            if field.geography:
+                index_ops = ''
+            elif self.connection.ops.geometry:
+                if field.dim > 2:
+                    index_ops = self.geom_index_ops_nd
+                else:
+                    index_ops = ''
+            else:
+                index_ops = self.geom_index_ops
+            output.append(
+                self.sql_add_spatial_index % {
+                    "index": self.quote_name('%s_%s_id' % (model._meta.db_table, field.column)),
+                    "table": self.quote_name(model._meta.db_table),
+                    "column": self.quote_name(field.column),
+                    "index_type": self.geom_index_type,
+                    "ops": index_ops,
+                }
+            )
+
+        return output