app/django/contrib/gis/db/backend/mysql/query.py
author Sverre Rabbelier <srabbelier@gmail.com>
Fri, 23 Jan 2009 21:20:33 +0000
changeset 935 09f47e08f805
parent 323 ff1a9aa48cfd
permissions -rw-r--r--
Adust the as_table tag to render a pick link if appropriate The templates are adjusted to pass on a 'reference' value, which is the url_name of the view from which the entity should be picked. The as_table (and related) function(s) construct and then pass on this argument and enable takes_contex so that we have access to the context of the enclosing template. We only extract ReferenceProperties that end with '_link_id' since that is how all RP's are currently named. It is not possible to create a field with the same name as the RP, as GAE will try to interpret it's contents as the key of an entity before even calling any function we can override. Patch by: Sverre Rabbelier

"""
 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))