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"""
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))
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