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Re: Possible planner bug/regression introduced in 8.2.5

From: Jakub Ouhrabka <kuba(at)comgate(dot)cz>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: pgsql-bugs(at)postgresql(dot)org
Subject: Re: Possible planner bug/regression introduced in 8.2.5
Date: 2007-10-29 15:27:48
Message-ID: 4725FBF4.1080403@comgate.cz (view raw or flat)
Thread:
Lists: pgsql-bugs
Hi Tom,

>> ...probably have some cases like that in your real application.  But I'd
>> expect 8.2.4 to be equally slow because it also contains the code that
>> is slow in that scenario.  I'm hoping to get some time today to think
>> about how that could be fixed.
> 
> Please try the attached patch (in addition to the one I sent earlier).

I can confirm that now there is no regression between 8.2.4 and 
8.2.5+one-line-patch.

I've also tried your last patch but still for some queries there is long 
planning time, e.g. more than 30s on a fast machine for query with 14 
regularly JOINed tables plus 8 tables are LEFT OUTER JOINed (all normal 
joins are followed by all outer joins). All joins are constrained on 
pk/fk. Should this case run faster or is it simply too much for 
geqo=off? Shall I prepare a test case?

Thanks,

Kuba


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