From: Tom Lane <tgl@sss.pgh.pa.us>
To: Greg Smith <gsmith@gregsmith.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: count * performance issue
Date: Sat, 08 Mar 2008 01:13:12 -0500
Message-ID: <16334.1204956792@sss.pgh.pa.us> (raw)
In-Reply-To: <Pine.GSO.4.64.0803072348050.4777@westnet.com>
References: <f966c2ee0803052142l6a105678jfe2da92a0d9371@mail.gmail.com>
<47D00DB2.7040007@emolecules.com>
<18451.1204824562@sss.pgh.pa.us>
<200803071727.36146.josh@agliodbs.com>
<13345.1204940295@sss.pgh.pa.us>
<Pine.GSO.4.64.0803072348050.4777@westnet.com>
Greg Smith <gsmith@gregsmith.com> writes:
> I know when I'm playing with pgbench the primary key index on the big
> accounts table is 1/7 the size of the table, and when using that table
> heavily shared_buffers ends up being mostly filled with that index. The
> usage counts are so high on the index blocks relative to any section of
> the table itself that they're very sticky in memory. And that's toy data;
> on some of the webapps people want these accurate counts for the ratio of
> index size to table data is even more exaggerated (think web forum).
Remember that our TOAST mechanism acts to limit the width of the
main-table row.
regards, tom lane
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To: pgsql-performance@postgresql.org
Cc: tgl@sss.pgh.pa.us, gsmith@gregsmith.com
Subject: Re: count * performance issue
In-Reply-To: <16334.1204956792@sss.pgh.pa.us>
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