83 lines
3.2 KiB
Python
83 lines
3.2 KiB
Python
from django.db.models.fields import Field # Django base Field class
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# Quotename & geographic quotename, respectively
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from django.db import connection
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qn = connection.ops.quote_name
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from django.contrib.gis.db.backend.util import gqn
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from django.contrib.gis.db.backend.spatialite.query import GEOM_FROM_TEXT, TRANSFORM
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class SpatiaLiteField(Field):
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"""
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The backend-specific geographic field for SpatiaLite.
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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(...) OpenGIS 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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style.SQL_KEYWORD(str(int(not self.null))) +
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');')
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return sql
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def _geom_index(self, style, db_table):
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"Creates a spatial index for this geometry field."
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sql = (style.SQL_KEYWORD('SELECT ') +
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style.SQL_TABLE('CreateSpatialIndex') + '(' +
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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 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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OpenGIS AddGeometryColumn() function.
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"""
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# Getting the AddGeometryColumn() SQL necessary to create a OpenGIS
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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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SpatiaLite geometry columns are added by stored procedures;
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should be 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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Transform() and GeomFromText() function call(s).
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"""
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if value is None or value.srid == self.srid:
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return '%s(%%s,%s)' % (GEOM_FROM_TEXT, self.srid)
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else:
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# Adding Transform() to the SQL placeholder.
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return '%s(%s(%%s,%s), %s)' % (TRANSFORM, GEOM_FROM_TEXT, value.srid, self.srid)
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