| from django.db.backends.postgresql_psycopg2.introspection import DatabaseIntrospection |
| from django.contrib.gis.gdal import OGRGeomType |
| |
| class GeoIntrospectionError(Exception): |
| pass |
| |
| class PostGISIntrospection(DatabaseIntrospection): |
| # Reverse dictionary for PostGIS geometry types not populated until |
| # introspection is actually performed. |
| postgis_types_reverse = {} |
| |
| def get_postgis_types(self): |
| """ |
| Returns a dictionary with keys that are the PostgreSQL object |
| identification integers for the PostGIS geometry and/or |
| geography types (if supported). |
| """ |
| cursor = self.connection.cursor() |
| # The OID integers associated with the geometry type may |
| # be different across versions; hence, this is why we have |
| # to query the PostgreSQL pg_type table corresponding to the |
| # PostGIS custom data types. |
| oid_sql = 'SELECT "oid" FROM "pg_type" WHERE "typname" = %s' |
| try: |
| cursor.execute(oid_sql, ('geometry',)) |
| GEOM_TYPE = cursor.fetchone()[0] |
| postgis_types = { GEOM_TYPE : 'GeometryField' } |
| if self.connection.ops.geography: |
| cursor.execute(oid_sql, ('geography',)) |
| GEOG_TYPE = cursor.fetchone()[0] |
| # The value for the geography type is actually a tuple |
| # to pass in the `geography=True` keyword to the field |
| # definition. |
| postgis_types[GEOG_TYPE] = ('GeometryField', {'geography' : True}) |
| finally: |
| cursor.close() |
| |
| return postgis_types |
| |
| def get_field_type(self, data_type, description): |
| if not self.postgis_types_reverse: |
| # If the PostGIS types reverse dictionary is not populated, do so |
| # now. In order to prevent unnecessary requests upon connection |
| # intialization, the `data_types_reverse` dictionary is not updated |
| # with the PostGIS custom types until introspection is actually |
| # performed -- in other words, when this function is called. |
| self.postgis_types_reverse = self.get_postgis_types() |
| self.data_types_reverse.update(self.postgis_types_reverse) |
| return super(PostGISIntrospection, self).get_field_type(data_type, description) |
| |
| def get_geometry_type(self, table_name, geo_col): |
| """ |
| The geometry type OID used by PostGIS does not indicate the particular |
| type of field that a geometry column is (e.g., whether it's a |
| PointField or a PolygonField). Thus, this routine queries the PostGIS |
| metadata tables to determine the geometry type, |
| """ |
| cursor = self.connection.cursor() |
| try: |
| try: |
| # First seeing if this geometry column is in the `geometry_columns` |
| cursor.execute('SELECT "coord_dimension", "srid", "type" ' |
| 'FROM "geometry_columns" ' |
| 'WHERE "f_table_name"=%s AND "f_geometry_column"=%s', |
| (table_name, geo_col)) |
| row = cursor.fetchone() |
| if not row: raise GeoIntrospectionError |
| except GeoIntrospectionError: |
| if self.connection.ops.geography: |
| cursor.execute('SELECT "coord_dimension", "srid", "type" ' |
| 'FROM "geography_columns" ' |
| 'WHERE "f_table_name"=%s AND "f_geography_column"=%s', |
| (table_name, geo_col)) |
| row = cursor.fetchone() |
| |
| if not row: |
| raise Exception('Could not find a geometry or geography column for "%s"."%s"' % |
| (table_name, geo_col)) |
| |
| # OGRGeomType does not require GDAL and makes it easy to convert |
| # from OGC geom type name to Django field. |
| field_type = OGRGeomType(row[2]).django |
| |
| # Getting any GeometryField keyword arguments that are not the default. |
| dim = row[0] |
| srid = row[1] |
| field_params = {} |
| if srid != 4326: |
| field_params['srid'] = srid |
| if dim != 2: |
| field_params['dim'] = dim |
| finally: |
| cursor.close() |
| |
| return field_type, field_params |