Re: [PERFORM] Need indexes on empty tables for good performance ?

[Lenard, Rohan (Rohan)]

Actually the indexes on the child table do seem to get used - I just wanted to make sure there was no penalty not having indexes on the empty parent tables.   You are right - the parent is the best way to get at the unknown children ...  From: Thomas F. O'Connell [mailto:[EMAIL PROTECTED] Sent: Tuesday, August 30, 2005 6:15 AM To: Lenard, Rohan (Rohan) Cc: pgsql-performance@postgresql.org Subject: Re: [PERFORM] Need indexes on empty tables for good performance ? Rohan, You should note that in Postgres, indexes are not inherited by child tables. Also, it seems difficult to select from a child table whose name you don't know unless you access the parent. And if you are accessing the data via the parent, I'm reasonably certain that you will find that indexes aren't used (even if they exist on the children) as a result of the way the children are accessed. -- Thomas F. O'Connell Co-Founder, Information Architect Sitening, LLC Strategic Open Source: Open Your i™ http://www.sitening.com/ 110 30th Avenue North, Suite 6 Nashville, TN 37203-6320 615-469-5150 615-469-5151 (fax) On Aug 22, 2005, at 10:41 PM, Lenard, Rohan (Rohan) wrote: I've read that indexes aren't used for COUNT(*) and I've noticed (7.3.x) with EXPLAIN that indexes never seem to be used on empty tables - is there any reason to have indexes on empty tables, or will postgresql never use them.   This is not as silly as it sounds - with table inheritance you might have table children with the data and a parent that is empty.  It'd be nice to make sure postgresql knows to never really look at the parent - especially is you don't know the names of all the children ..   Thoughts ?   thx,   Rohan