Thanks for your reply.
What you propose would work for me, but in the meantime I need a workaround.
I thought of serializing the arrays in SQL, then converting back to tuples
in my code, but the objects contained in the arrays are quite complex to
parse (decimals, datetims...). So I tried patching the ARRAY class to return
tuples when mutable=False, and that had no effect. If I understand
correctly, by the time unique_list() is called, ARRAY hasn't been involved
yet, and the database's array is converted to a Python list by the driver
(psycopg2 in my case).
The workaround I've found is to make the following change, in
sqlalchemy.orm.query.Query.instances :
if filtered:
#if single_entity:
# filter = lambda x: util.unique_list(x, util.IdentitySet)
#else:
# filter = util.unique_list
filter = lambda x: util.unique_list(x, util.IdentitySet)
Should I expect negative side-effects from this?
-----Message d'origine-----
De : sqlalchemy@googlegroups.com [mailto:sqlalch...@googlegroups.com] De la
part de Michael Bayer
Envoyé : mercredi 13 octobre 2010 23:37
À : sqlalchemy@googlegroups.com
Objet : Re: [sqlalchemy] Cannot retrieve PostgreSQL array column with
session.query() : TypeError: unhashable type: 'list'
The Query runs the result through unique_list() anytime there are mapped
entities in the columns list. The ARRAY result, returning a Python list
[], isn't hashable, so thats that.
If you only queried for columns, it wouldn't be running through
unique_list().
I suppose we'd modify ARRAY to return tuples if it's "mutable" flag isn't
set. that could only be in 0.7, though. Let me know if that works for
you, we'll add a ticket (hard for me to say since I never use the ARRAY
type).
On Oct 13, 2010, at 2:22 PM, Julien Demoor wrote:
> Hello,
>
> The problem I'm seeing is illustrated by the code below. I tried a
> workaround using TypeDecorator with process_result_value returning a
> tuple rather than a list, to no avail.
>
> Any help will be greatly appreciated.
>
> Regards.
>
> Traceback :
>
> Traceback (most recent call last):
> File "satest2.py", line 23, in <module>
> session.query(Foo, 'col').from_statement("SELECT 55 AS foo_bar,
> '{1,2,3}'::integer[] AS col;").first()
> File "/home/user/programs/env/lib/python2.6/site-packages/sqlalchemy/
> orm/query.py", line 1494, in first
> ret = list(self)[0:1]
> File "/home/user/programs/env/lib/python2.6/site-packages/sqlalchemy/
> orm/query.py", line 1682, in instances
> rows = filter(rows)
> File "/home/jdemoor/programs/km/lib/python2.6/site-packages/
> sqlalchemy/util.py", line 1193, in unique_list
> return [x for x in seq if x not in seen and not seen.add(x)]
> TypeError: unhashable type: 'list'
>
> Full code :
>
> import os
> from sqlalchemy import create_engine, Table, Integer, MetaData, Column
> from sqlalchemy.orm import create_session, mapper
>
> sa_engine = create_engine(os.environ['TEST_DSN'])
> session = create_session(sa_engine, autoflush=True,
> expire_on_commit=True, autocommit=False)
>
> metadata = MetaData()
> foo = Table('foo', metadata, Column('bar', Integer, primary_key=True))
> class Foo(object):
> pass
> mapper(Foo, foo)
>
> # This works
> assert session.query('col').from_statement("SELECT 'abc' AS
> col;").first() == ('abc',)
> assert session.query('col').from_statement("SELECT
> '{1,2,3}'::integer[] AS col;").first() == ([1,2,3],)
> assert session.query('col1', 'col2').from_statement("SELECT
> '{1,2,3}'::integer[] AS col1, 'abc' AS col2;").first() == ([1,2,3],
> 'abc')
> foo_obj = session.query(Foo).from_statement("SELECT 1 AS
> foo_bar;").first()
> assert foo_obj.bar == 1
>
> try:
> # This fails
> session.query(Foo, 'col').from_statement("SELECT 55 AS foo_bar,
> '{1,2,3}'::integer[] AS col;").first()
> except TypeError, e:
> print e
>
> from sqlalchemy.dialects.postgresql.base import ARRAY
> col = Column('col', ARRAY(Integer, mutable=False))
> try:
> # This fails too
> session.query(Foo, col).from_statement("SELECT 55 AS foo_bar,
> '{1,2,3}'::integer[] AS col;").first()
> except TypeError, e:
> print e
>
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