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