60 lines
2.2 KiB
Python
60 lines
2.2 KiB
Python
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"""
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This module contains the spatial lookup types, and the `get_geo_where_clause`
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routine for MySQL.
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Please note that MySQL only supports bounding box queries, also
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known as MBRs (Minimum Bounding Rectangles). Moreover, spatial
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indices may only be used on MyISAM tables -- if you need
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transactions, take a look at PostGIS.
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"""
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from django.db import connection
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qn = connection.ops.quote_name
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# To ease implementation, WKT is passed to/from MySQL.
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GEOM_FROM_TEXT = 'GeomFromText'
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GEOM_FROM_WKB = 'GeomFromWKB'
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GEOM_SELECT = 'AsText(%s)'
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# WARNING: MySQL is NOT compliant w/the OpenGIS specification and
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# _every_ one of these lookup types is on the _bounding box_ only.
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MYSQL_GIS_FUNCTIONS = {
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'bbcontains' : 'MBRContains', # For consistency w/PostGIS API
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'bboverlaps' : 'MBROverlaps', # .. ..
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'contained' : 'MBRWithin', # .. ..
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'contains' : 'MBRContains',
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'disjoint' : 'MBRDisjoint',
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'equals' : 'MBREqual',
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'exact' : 'MBREqual',
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'intersects' : 'MBRIntersects',
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'overlaps' : 'MBROverlaps',
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'same_as' : 'MBREqual',
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'touches' : 'MBRTouches',
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'within' : 'MBRWithin',
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}
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# This lookup type does not require a mapping.
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MISC_TERMS = ['isnull']
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# Assacceptable lookup types for Oracle spatial.
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MYSQL_GIS_TERMS = MYSQL_GIS_FUNCTIONS.keys()
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MYSQL_GIS_TERMS += MISC_TERMS
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MYSQL_GIS_TERMS = dict((term, None) for term in MYSQL_GIS_TERMS) # Making dictionary
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def get_geo_where_clause(table_alias, name, lookup_type, geo_annot):
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"Returns the SQL WHERE clause for use in MySQL spatial SQL construction."
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# Getting the quoted field as `geo_col`.
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geo_col = '%s.%s' % (qn(table_alias), qn(name))
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# See if a MySQL Geometry function matches the lookup type next
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lookup_info = MYSQL_GIS_FUNCTIONS.get(lookup_type, False)
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if lookup_info:
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return "%s(%s, %%s)" % (lookup_info, geo_col)
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# Handling 'isnull' lookup type
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# TODO: Is this needed because MySQL cannot handle NULL
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# geometries in its spatial indices.
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if lookup_type == 'isnull':
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return "%s IS %sNULL" % (geo_col, (not geo_annot.value and 'NOT ' or ''))
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raise TypeError("Got invalid lookup_type: %s" % repr(lookup_type))
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