app/django/contrib/gis/db/backend/mysql/query.py
author Lennard de Rijk <ljvderijk@gmail.com>
Sun, 01 Feb 2009 17:14:42 +0000
changeset 1157 76e2ed09661c
parent 323 ff1a9aa48cfd
permissions -rw-r--r--
Added status property to the user model. This is to accommodate the ability to exclude users from using the website. Note that since the access modules is currently undergoing some reconstruction changing the status will not actually effect the User yet. Patch by: Lennard de Rijk Reviewed by: to-be-reviewed

"""
 This module contains the spatial lookup types, and the `get_geo_where_clause`
 routine for MySQL.

 Please note that MySQL only supports bounding box queries, also
 known as MBRs (Minimum Bounding Rectangles).  Moreover, spatial
 indices may only be used on MyISAM tables -- if you need 
 transactions, take a look at PostGIS.
"""
from django.db import connection
qn = connection.ops.quote_name

# To ease implementation, WKT is passed to/from MySQL.
GEOM_FROM_TEXT = 'GeomFromText'
GEOM_FROM_WKB = 'GeomFromWKB'
GEOM_SELECT = 'AsText(%s)'

# WARNING: MySQL is NOT compliant w/the OpenGIS specification and
# _every_ one of these lookup types is on the _bounding box_ only.
MYSQL_GIS_FUNCTIONS = {
    'bbcontains' : 'MBRContains', # For consistency w/PostGIS API
    'bboverlaps' : 'MBROverlaps', # .. ..
    'contained' : 'MBRWithin',    # .. ..
    'contains' : 'MBRContains',
    'disjoint' : 'MBRDisjoint',
    'equals' : 'MBREqual',
    'exact' : 'MBREqual',
    'intersects' : 'MBRIntersects',
    'overlaps' : 'MBROverlaps',
    'same_as' : 'MBREqual',
    'touches' : 'MBRTouches',
    'within' : 'MBRWithin',
    }

# This lookup type does not require a mapping.
MISC_TERMS = ['isnull']

# Assacceptable lookup types for Oracle spatial.
MYSQL_GIS_TERMS  = MYSQL_GIS_FUNCTIONS.keys()
MYSQL_GIS_TERMS += MISC_TERMS
MYSQL_GIS_TERMS = dict((term, None) for term in MYSQL_GIS_TERMS) # Making dictionary 

def get_geo_where_clause(table_alias, name, lookup_type, geo_annot):
    "Returns the SQL WHERE clause for use in MySQL spatial SQL construction."
    # Getting the quoted field as `geo_col`.
    geo_col = '%s.%s' % (qn(table_alias), qn(name))

    # See if a MySQL Geometry function matches the lookup type next
    lookup_info = MYSQL_GIS_FUNCTIONS.get(lookup_type, False)
    if lookup_info:
        return "%s(%s, %%s)" % (lookup_info, geo_col)
    
    # Handling 'isnull' lookup type
    # TODO: Is this needed because MySQL cannot handle NULL
    # geometries in its spatial indices.
    if lookup_type == 'isnull':
        return "%s IS %sNULL" % (geo_col, (not geo_annot.value and 'NOT ' or ''))

    raise TypeError("Got invalid lookup_type: %s" % repr(lookup_type))