One of the big changes in PostGIS 2.0 was that the geometry_columns table became a read only view. This change was not without sacrifice. On the plus
it meant a table no longer needed to be maintained which was a relief for those who had to constantly ensure the sideline table was up to date. Also on the plus it meant we could base the views on the current user so that if a user connected, they would only see tables they had access to. The sacrifice made was a bit of speed. In most use cases, the speed difference is hardly noticeable
and only noticeable if you have a query constantly polling this table. However if you have a database of 15,000 geometry tables it could take as long as 450ms as noted in this ticket.
So just playing with ideas, could the new PostgreSQL 9.3 event triggers and materialized views provide a solution. Keep in mind this is just food
for thought. We're not condoning people go out and hack their PostGIS install. We suspect if we implement such a thing in PostGIS core it will change from what we propose here.
If you saw our prior article Caching data with materialized views and statement level triggers you know where this is going. We'll add yet another concept to this cocktail and that is what we'll call schema hiding which by that we mean counting on the order of a search_path to hide a named table/view you don't want.