Hi
I'm facing another column_expression issue. It is not related to the
previous issue, and I'm sure if SQLAlchemy can help me with this one.
----
from sqlalchemy.types import UserDefinedType
from sqlalchemy.sql import func
class Geometry(UserDefinedType):
def column_expression(self, col):
return func.ST_AsBinary(col, type_=self)
from sqlalchemy import Table, Column, MetaData
lakes = Table('lake', MetaData(),
Column('geom', Geometry)
)
from sqlalchemy.sql.expression import select, alias
s = select([lakes])
a = alias(s, 'name')
s = a.select()
print s
----
The print statement returns this:
SELECT ST_AsBinary(name.geom) AS geom FROM (SELECT
ST_AsBinary(lake.geom) AS geom FROM lake) AS name
Which is expected. But the execution of this statement fails in my
PostGIS database, because ST_AsBinary cannot receive a bytea value as
input. (the outer ST_AsBinary call receives what's returned from the
inner ST_AsBinary call). It would work if ST_AsBinary was idempotent,
but it's not in PostGIS 2
(<http://trac.osgeo.org/postgis/ticket/1869>).
I'm stuck on this one.
--
Eric Lemoine
Camptocamp France SAS
Savoie Technolac, BP 352
73377 Le Bourget du Lac, Cedex
Tel : 00 33 4 79 44 44 96
Mail : eric.lemo...@camptocamp.com
http://www.camptocamp.com
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