| 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) |