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from django.db.models.lookups import Lookup
from django.db.models.sql.expressions import SQLEvaluator
class GISLookup(Lookup):
def as_sql(self, qn, connection):
from django.contrib.gis.db.models.sql import GeoWhereNode
# We use the same approach as was used by GeoWhereNode. It would
# be a good idea to upgrade GIS to use similar code that is used
# for other lookups.
if isinstance(self.rhs, SQLEvaluator):
# Make sure the F Expression destination field exists, and
# set an `srid` attribute with the same as that of the
# destination.
geo_fld = GeoWhereNode._check_geo_field(self.rhs.opts, self.rhs.expression.name)
if not geo_fld:
raise ValueError('No geographic field found in expression.')
self.rhs.srid = geo_fld.srid
db_type = self.lhs.output_field.db_type(connection=connection)
params = self.lhs.output_field.get_db_prep_lookup(
self.lookup_name, self.rhs, connection=connection)
lhs_sql, lhs_params = self.process_lhs(qn, connection)
# lhs_params not currently supported.
assert not lhs_params
data = (lhs_sql, db_type)
spatial_sql, spatial_params = connection.ops.spatial_lookup_sql(
data, self.lookup_name, self.rhs, self.lhs.output_field, qn)
return spatial_sql, spatial_params + params
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