"Tom Lane" <[EMAIL PROTECTED]> writes: > Gregory Stark <[EMAIL PROTECTED]> writes: >> The screw case I've seen is when you have a large partitioned table where >> constraint_exclusion fails to exclude the irrelevant partitions. You're going >> to get 0 rows from all but the one partition which contains the 1 row you're >> looking for. But since each partition is clamped to 1 you end up with an >> estimate of a few hundred rows coming out of the Append node. > >> The natural way to kill this is to allow fractional rows for these scans. > > No, the right fix is to fix the constraint-exclusion failure.
There are always going to be cases where that's not possible. It's possible that the second option I described -- teaching Append when to use something other than sum() -- would only work in the cases where constraint exclusion could be fixed though. In which case having fractional row counts might actually be necessary. -- Gregory Stark EnterpriseDB http://www.enterprisedb.com Ask me about EnterpriseDB's Slony Replication support! -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
