From: Michael Stone <mstone+postgres@mathom.us>
To: pgsql-performance@postgresql.org, Peter Eisentraut <peter_e@gmx.net>
Subject: Re: Index scan startup time
Date: Thu, 30 Mar 2006 08:29:17 -0500
Message-ID: <20060330132915.GL6811@mathom.us> (raw)
In-Reply-To: <20060330125147.GA13611@uio.no>
References: <200603301359.11038.peter_e@gmx.net>
<20060330120206.GA13075@uio.no>
<200603301423.54510.peter_e@gmx.net>
<20060330123134.GA13408@uio.no>
<20060330124251.GK6811@mathom.us>
<20060330125147.GA13611@uio.no>
On Thu, Mar 30, 2006 at 02:51:47PM +0200, Steinar H. Gunderson wrote:
>On Thu, Mar 30, 2006 at 07:42:53AM -0500, Michael Stone wrote:
>> Yes. And the estimates are bad enough (orders of magnitude) that I can't
>> help but wonder whether pg could come up with a better plan with better
>> statistics:
>>
>>>>>> -> Index Scan using activity_pk on activity (cost=0.00..40717259.91
>>>>>> rows=6538650 width=8) (actual time=207356.050..207356.722 rows=100
>>>>>> loops=1) Filter: ((state = 10000) OR (state = 10001))
>
>Isn't the rows=100 here because of the LIMIT?
Yes. I was looking at the other side; I thought pg could estimate how
much work it would have to do to hit the limit, but double-checking it
looks like it can't.
Mike Stone
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To: pgsql-performance@postgresql.org
Cc: mstone+postgres@mathom.us, peter_e@gmx.net
Subject: Re: Index scan startup time
In-Reply-To: <20060330132915.GL6811@mathom.us>
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