1 from django.db.models.fields import Field # Django base Field class

     2 

     3 # Quotename & geographic quotename, respectively

     4 from django.db import connection

     5 qn = connection.ops.quote_name

     6 from django.contrib.gis.db.backend.util import gqn

     7 from django.contrib.gis.db.backend.spatialite.query import GEOM_FROM_TEXT, TRANSFORM

     8 

     9 class SpatiaLiteField(Field):

    10     """

    11     The backend-specific geographic field for SpatiaLite.

    12     """

    13 

    14     def _add_geom(self, style, db_table):

    15         """

    16         Constructs the addition of the geometry to the table using the

    17         AddGeometryColumn(...) OpenGIS stored procedure.

    18 

    19         Takes the style object (provides syntax highlighting) and the

    20         database table as parameters.

    21         """

    22         sql = (style.SQL_KEYWORD('SELECT ') +

    23                style.SQL_TABLE('AddGeometryColumn') + '(' +

    24                style.SQL_TABLE(gqn(db_table)) + ', ' +

    25                style.SQL_FIELD(gqn(self.column)) + ', ' +

    26                style.SQL_FIELD(str(self.srid)) + ', ' +

    27                style.SQL_COLTYPE(gqn(self.geom_type)) + ', ' +

    28                style.SQL_KEYWORD(str(self.dim)) + ', ' +

    29                style.SQL_KEYWORD(str(int(not self.null))) +

    30                ');')

    31         return sql

    32 

    33     def _geom_index(self, style, db_table):

    34         "Creates a spatial index for this geometry field."

    35         sql = (style.SQL_KEYWORD('SELECT ') +

    36               style.SQL_TABLE('CreateSpatialIndex') + '(' +

    37               style.SQL_TABLE(gqn(db_table)) + ', ' +

    38               style.SQL_FIELD(gqn(self.column)) + ');')

    39         return sql

    40 

    41     def post_create_sql(self, style, db_table):

    42         """

    43         Returns SQL that will be executed after the model has been

    44         created. Geometry columns must be added after creation with the

    45         OpenGIS AddGeometryColumn() function.

    46         """

    47         # Getting the AddGeometryColumn() SQL necessary to create a OpenGIS

    48         # geometry field.

    49         post_sql = self._add_geom(style, db_table)

    50 

    51         # If the user wants to index this data, then get the indexing SQL as well.

    52         if self.spatial_index:

    53             return (post_sql, self._geom_index(style, db_table))

    54         else:

    55             return (post_sql,)

    56 

    57     def _post_delete_sql(self, style, db_table):

    58         "Drops the geometry column."

    59         sql = (style.SQL_KEYWORD('SELECT ') +

    60                style.SQL_KEYWORD('DropGeometryColumn') + '(' +

    61                style.SQL_TABLE(gqn(db_table)) + ', ' +

    62                style.SQL_FIELD(gqn(self.column)) +  ');')

    63         return sql

    64 

    65     def db_type(self):

    66         """

    67         SpatiaLite geometry columns are added by stored procedures;

    68         should be None.

    69         """

    70         return None

    71 

    72     def get_placeholder(self, value):

    73         """

    74         Provides a proper substitution value for Geometries that are not in the

    75         SRID of the field.  Specifically, this routine will substitute in the

    76         Transform() and GeomFromText() function call(s).

    77         """

    78         if value is None or value.srid == self.srid:

    79             return '%s(%%s,%s)' % (GEOM_FROM_TEXT, self.srid)

    80         else:

    81             # Adding Transform() to the SQL placeholder.

    82             return '%s(%s(%%s,%s), %s)' % (TRANSFORM, GEOM_FROM_TEXT, value.srid, self.srid)