Re: Fwd: 8.2 Query 10 times slower than 8.1 (view-heavy)

Mark Lewis <mark(dot)lewis(at)mir3(dot)com> writes:
> Unfortunately there has been a planner regression in 8.2 in some cases
> with these forms of queries. This was discussed a few weeks (months?)
> ago on this forum. I haven't looked closely enough to confirm that this
> is the problem in your case, but it seems likely.

Yeah, the EXPLAIN ANALYZE output clearly shows a drastic underestimate
of the number of rows out of a join like this, and a consequent choice
of a nestloop above it that performs terribly.

> We've been holding back from upgrading to 8.2 because this one is a
> show-stopper for us.

Well, you could always make your own version with this patch reverted:
http://archives.postgresql.org/pgsql-committers/2006-11/msg00066.php

I might end up doing that in the 8.2 branch if a better solution
seems too large to back-patch.

regards, tom lane