96 lines
3.6 KiB
Python
96 lines
3.6 KiB
Python
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_type)) + ', ' +
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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.spatial_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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