The enclosed two liners does fix the tests when running
on a postgresql 8.3 backend.

After patching, I've ran the tests on postgresql (both 8.3 and 8.1), on mysql 5.0.51 and pysqlite2 (running on libsqlite ver. 3.5.9).

I've no previous mysql or postgres install handy, but the changes seem harmless enough to get in asap...