From: | "Steinar H(dot) Gunderson" <sgunderson(at)bigfoot(dot)com> |
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To: | pgsql-performance(at)postgresql(dot)org |
Subject: | Re: Index scan startup time |
Date: | 2006-03-30 13:00:41 |
Message-ID: | 20060330130041.GA13732@uio.no |
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Lists: | pgsql-performance |
On Thu, Mar 30, 2006 at 02:59:02PM +0200, Peter Eisentraut wrote:
>> Well, it's logical enough; it scans along activity_id until it finds one
>> with state=10000 or state=10001. You obviously have a _lot_ of records with
>> low activity_id and state none of these two, so Postgres needs to scan all
>> those records before it founds 100 it can output. This is the “startup
>> cost” you're seeing.
> The startup cost is the cost until the plan is set up to start outputting
> rows. It is not the time until the first row is found.
Well, point, my terminology was wrong. Still, what you're seeing is endless
scanning for the first row. I don't know your distribution, but are you
really sure state wouldn't have better selectivity?
/* Steinar */
--
Homepage: http://www.sesse.net/
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