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Re: performance penalty between Postgresql 8.3.8 and 8.4.1

From: Andres Freund <andres(at)anarazel(dot)de>
To: pgsql-performance(at)postgresql(dot)org
Cc: "Schmitz, David" <david(dot)schmitz(at)harman(dot)com>
Subject: Re: performance penalty between Postgresql 8.3.8 and 8.4.1
Date: 2009-12-08 10:28:55
Message-ID: 200912081128.56076.andres@anarazel.de (view raw or flat)
Thread:
Lists: pgsql-performance
Hi David,

On Tuesday 08 December 2009 10:59:51 Schmitz, David wrote:
> >> With our data it is a performance difference from 1h16min
> >> (8.3.8) to 2h43min (8.4.1)
> On Postgresql 8.4.1
> Total runtime: 101.446 ms
> and on Postgresql  8.3.8:
> Total runtime: 29.366 ms
Hm. There obviously is more going on than these queries?

> Hash Join  (cost=2603.57..124518.03 rows=60772 width=61) (actual 
time=62.359..97.268 rows=1444 loops=1)
> Nested Loop  (cost=21.00..3790.18 rows=81 width=61) (actual 
time=0.210..26.098 rows=1444 loops=1)
Both misestimate the resultset quite a bit. It looks like happenstance that 
the one on 8.3 turns out to be better...

Andres

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