get_table_names() and get_column_names() wrongly return an empty list when schema is not used on PostgreSQL

[Jun Omae]

Python 2.5.6 (r256:88840, Oct 21 2014, 22:49:55)
[GCC 4.8.2] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> from trac.env import Environment
>>> from trac.db.api import DatabaseManager
>>> env = Environment('/dev/shm/postgres-without-schema')
>>> dbm = DatabaseManager(env)
>>> dbm.connection_uri
u'postgres://tracuser:password@127.1/tractest'
>>> with env.db_query as db:
...   db.get_table_names()
...
[]
>>> with env.db_query as db:
...   db.get_column_names('wiki')
...
[]
>>> env.db_query("""
...   SELECT table_name FROM information_schema.tables
...   WHERE table_schema=current_schema()
...   ORDER BY table_name
... """)
[(u'attachment',), (u'auth_cookie',), (u'cache',), (u'component',), (u'enum',), (u'milestone',), (u'node_change',), (u'permission',), (u'report',), (u'repository',), (u'revision',), (u'session',), (u'session_attribute',), (u'system',), (u'ticket',), (u'ticket_change',), (u'ticket_custom',), (u'version',), (u'wiki',)]
>>> env.db_query("""
...   SELECT column_name FROM information_schema.columns
...   WHERE table_schema=current_schema() AND table_name=%s
...   """, ('wiki',))
[(u'readonly',), (u'comment',), (u'text',), (u'ipnr',), (u'author',), (u'time',), (u'version',), (u'name',)]