61 lines
2.9 KiB
Python
61 lines
2.9 KiB
Python
from django.contrib.gis.gdal import OGRGeomType
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from django.db.backends.postgresql.introspection import DatabaseIntrospection
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class PostGISIntrospection(DatabaseIntrospection):
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postgis_oid_lookup = {} # Populated when introspection is performed.
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ignored_tables = DatabaseIntrospection.ignored_tables + [
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'geography_columns',
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'geometry_columns',
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'raster_columns',
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'spatial_ref_sys',
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'raster_overviews',
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]
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def get_field_type(self, data_type, description):
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if not self.postgis_oid_lookup:
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# Query PostgreSQL's pg_type table to determine the OID integers
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# for the PostGIS data types used in reverse lookup (the integers
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# may be different across versions). To prevent unnecessary
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# requests upon connection initialization, the `data_types_reverse`
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# dictionary isn't updated until introspection is performed here.
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with self.connection.cursor() as cursor:
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cursor.execute("SELECT oid, typname FROM pg_type WHERE typname IN ('geometry', 'geography')")
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self.postgis_oid_lookup = dict(cursor.fetchall())
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self.data_types_reverse.update((oid, 'GeometryField') for oid in self.postgis_oid_lookup)
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return super().get_field_type(data_type, description)
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def get_geometry_type(self, table_name, description):
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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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with self.connection.cursor() as cursor:
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cursor.execute("""
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SELECT t.coord_dimension, t.srid, t.type FROM (
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SELECT * FROM geometry_columns
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UNION ALL
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SELECT * FROM geography_columns
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) AS t WHERE t.f_table_name = %s AND t.f_geometry_column = %s
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""", (table_name, description.name))
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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, description.name))
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dim, srid, field_type = row
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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(field_type).django
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# Getting any GeometryField keyword arguments that are not the default.
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field_params = {}
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if self.postgis_oid_lookup.get(description.type_code) == 'geography':
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field_params['geography'] = True
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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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return field_type, field_params
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