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