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Re: Index scan startup time

From: Michael Stone <mstone+postgres(at)mathom(dot)us>
To: pgsql-performance(at)postgresql(dot)org, Peter Eisentraut <peter_e(at)gmx(dot)net>
Subject: Re: Index scan startup time
Date: 2006-03-30 13:29:17
Message-ID: 20060330132915.GL6811@mathom.us (view raw or flat)
Thread:
Lists: pgsql-performance
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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