On Mon, May 13, 2013 at 6:01 PM, ach <alanchi...@gmail.com> wrote: > what I'm wondering is, since > the unique constraint already covers the whole table and all rows in > entirety, is it really necessary for statistics to be set that high on > those?
AFAIK if there are exact-matching unique constraints/indexes for a query's WHERE clause, the planner will deduce that the query only returns 1 row and won't consult statistics at all. > Or does that only serve to slow down inserts to that table? It doesn't slow down inserts directly. Tables are analyzed in the background by autovacuum. However, I/O traffic from autovacuum analyze may slow down inserts running concurrently. Regards, Marti -- Sent via pgsql-performance mailing list (pgsql-performance@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
