Re: Left Join Performance vs Inner Join Performance

From: Tom Lane
Subject: Re: Left Join Performance vs Inner Join Performance
Date: ,
Msg-id: 8321.1136954300@sss.pgh.pa.us
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In response to: Left Join Performance vs Inner Join Performance  ("Dave Dutcher")
List: pgsql-performance

"Dave Dutcher" <> writes:
> I have an inner join query that runs fast, but I when I change to a left
> join the query runs 96 times slower.

This looks like an issue that is fixed in the latest set of releases,
namely that OUTER JOIN ON conditions that reference only the inner
side of the join weren't getting pushed down into indexquals.  See
thread here:
http://archives.postgresql.org/pgsql-performance/2005-12/msg00134.php
and patches in this and the following messages:
http://archives.postgresql.org/pgsql-committers/2005-12/msg00105.php

            regards, tom lane


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