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:
I might end up doing that in the 8.2 branch if a better solution
seems too large to back-patch.
regards, tom lane
In response to
pgsql-performance by date
|Next:||From: Kari Lavikka||Date: 2007-08-28 18:53:37|
|Subject: Performance problem with table containing a lot of text (blog)|
|Previous:||From: Tom Lane||Date: 2007-08-28 18:36:13|
|Subject: Re: 8.2.4 Chooses Bad Query Plan |