"Tom Lane" <[EMAIL PROTECTED]> writes: > Right. As a matter of policy we never estimate less than one matching > row; and I've seriously considered pushing that up to at least two rows > except when we see that the query condition matches a unique constraint. > You can get really bad join plans from overly-small estimates.
This is something that needs some serious thought though. In the case of partitioned tables I've seen someone get badly messed up plans because they had a couple hundred partitions each of which estimated to return 1 row. In fact of course they all returned 0 rows except the correct partition. (This was in a join so no constraint exclusion) -- Gregory Stark EnterpriseDB http://www.enterprisedb.com Ask me about EnterpriseDB's 24x7 Postgres support! -- Sent via pgsql-performance mailing list (pgsql-performance@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
