Don't restrict sessid compat. check to a single run. Reset cached column info before checking in case it's stale (may happen if you change table_name). Make the test a private class method.
git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@1693 5ecf4fe2-1ee6-0310-87b1-e25e094e27de