--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/app/django/contrib/gis/db/backend/postgis/field.py	Tue Oct 14 16:00:59 2008 +0000
@@ -0,0 +1,95 @@
+from django.db import connection
+from django.db.models.fields import Field # Django base Field class
+from django.contrib.gis.db.backend.util import gqn
+from django.contrib.gis.db.backend.postgis.query import TRANSFORM
+
+# Quotename & geographic quotename, respectively
+qn = connection.ops.quote_name
+
+class PostGISField(Field):
+    """
+    The backend-specific geographic field for PostGIS.
+    """
+
+    def _add_geom(self, style, db_table):
+        """
+        Constructs the addition of the geometry to the table using the
+        AddGeometryColumn(...) PostGIS (and OGC standard) stored procedure.
+
+        Takes the style object (provides syntax highlighting) and the
+        database table as parameters.
+        """
+        sql = style.SQL_KEYWORD('SELECT ') + \
+              style.SQL_TABLE('AddGeometryColumn') + '(' + \
+              style.SQL_TABLE(gqn(db_table)) + ', ' + \
+              style.SQL_FIELD(gqn(self.column)) + ', ' + \
+              style.SQL_FIELD(str(self._srid)) + ', ' + \
+              style.SQL_COLTYPE(gqn(self._geom)) + ', ' + \
+              style.SQL_KEYWORD(str(self._dim)) + ');'
+
+        if not self.null:
+            # Add a NOT NULL constraint to the field
+            sql += '\n' + \
+                   style.SQL_KEYWORD('ALTER TABLE ') + \
+                   style.SQL_TABLE(qn(db_table)) + \
+                   style.SQL_KEYWORD(' ALTER ') + \
+                   style.SQL_FIELD(qn(self.column)) + \
+                   style.SQL_KEYWORD(' SET NOT NULL') + ';'
+        return sql
+    
+    def _geom_index(self, style, db_table,
+                    index_type='GIST', index_opts='GIST_GEOMETRY_OPS'):
+        "Creates a GiST index for this geometry field."
+        sql = style.SQL_KEYWORD('CREATE INDEX ') + \
+              style.SQL_TABLE(qn('%s_%s_id' % (db_table, self.column))) + \
+              style.SQL_KEYWORD(' ON ') + \
+              style.SQL_TABLE(qn(db_table)) + \
+              style.SQL_KEYWORD(' USING ') + \
+              style.SQL_COLTYPE(index_type) + ' ( ' + \
+              style.SQL_FIELD(qn(self.column)) + ' ' + \
+              style.SQL_KEYWORD(index_opts) + ' );'
+        return sql
+
+    def post_create_sql(self, style, db_table):
+        """
+        Returns SQL that will be executed after the model has been
+        created. Geometry columns must be added after creation with the
+        PostGIS AddGeometryColumn() function.
+        """
+
+        # Getting the AddGeometryColumn() SQL necessary to create a PostGIS
+        # geometry field.
+        post_sql = self._add_geom(style, db_table)
+
+        # If the user wants to index this data, then get the indexing SQL as well.
+        if self._index:
+            return (post_sql, self._geom_index(style, db_table))
+        else:
+            return (post_sql,)
+
+    def _post_delete_sql(self, style, db_table):
+        "Drops the geometry column."
+        sql = style.SQL_KEYWORD('SELECT ') + \
+            style.SQL_KEYWORD('DropGeometryColumn') + '(' + \
+            style.SQL_TABLE(gqn(db_table)) + ', ' + \
+            style.SQL_FIELD(gqn(self.column)) +  ');'
+        return sql
+
+    def db_type(self):
+        """
+        PostGIS geometry columns are added by stored procedures, should be
+        None.
+        """
+        return None
+
+    def get_placeholder(self, value):
+        """
+        Provides a proper substitution value for Geometries that are not in the
+        SRID of the field.  Specifically, this routine will substitute in the
+        ST_Transform() function call.
+        """
+        if value is None or value.srid == self._srid:
+            return '%s'
+        else:
+            # Adding Transform() to the SQL placeholder.
+            return '%s(%%s, %s)' % (TRANSFORM, self._srid)