Re: Blocks read for index scans

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Jim Nasby <jnasby(at)pervasive(dot)com>
Cc: Postgresql Performance <pgsql-performance(at)postgresql(dot)org>
Subject: Re: Blocks read for index scans
Date: 2006-04-14 00:36:09
Message-ID: 2789.1144974969@sss.pgh.pa.us
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Jim Nasby <jnasby(at)pervasive(dot)com> writes:
> While working on determining a good stripe size for a database, I
> realized it would be handy to know what the average request size is.
> Getting this info is a simple matter of joining pg_stat_all_tables
> and pg_statio_all_tables and doing some math, but there's one issue
> I've found; it appears that there's no information on how many heap
> blocks were read in by an index scan. Is there any way to get that info?

If the table is otherwise idle, the change in the table's entry in
pgstatio_all_tables should do, no?

(This is as of 8.1 ... older versions acted a bit differently IIRC.)

regards, tom lane

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