Slow tab completion w/ lots of tables

Greetings,

When doing tab-completion under 9.1, pg_table_is_visible(oid) is slow
and is ending up as the first thing tested against all the rows
in pg_class. Increasing the cost of pg_table_is_visible() up to
10 causes it to move to the end of the tests, which improves things
greatly- I thought there was a plan to make that the default..?

This is with 9.1.4.

After researching this a bit, I'm left wondering why we're using
substring() to do the matching test. I don't see any easy way to
index a substring() call which can be of any size (depending on how
many characters are preceding the user hitting 'tab'). On the other
hand, using LIKE with 'string%' and indexing with varchar_pattern_ops
should give us a nice index which could be used for tab completion,
right? If no one points out an obvious flaw in that, I'll take a look
at making that happen.

Thanks!

Stephen