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Re: OUTER JOIN performance regression remains in 8.3beta4

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov>
Cc: pgsql-hackers(at)postgresql(dot)org, "Kevin Grittner" <Kgrittn(dot)CCAP(dot)Courts(at)wicourts(dot)gov>
Subject: Re: OUTER JOIN performance regression remains in 8.3beta4
Date: 2008-01-04 22:40:22
Message-ID: 23936.1199486422@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-patches
"Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov> writes:
> As I poked around at this, it started to seem familiar.  I had
> previously posted about this query's performance under 8.2.4.
> http://archives.postgresql.org/pgsql-performance/2007-10/msg00087.php

Well, that thread gave some of the missing details, such as

              Table "public.ControlRecord"
       Column       |          Type          | Modifiers
--------------------+------------------------+-----------
 countyNo           | "CountyNoT"            | not null

but what the heck is "CountyNoT"?

It looks like 8.3 is failing to realize that it can propagate the
countyNo = 53 condition down to this table's scan, as 8.2 did;
but there's not enough details here to guess why not.

			regards, tom lane

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