From: Tom Lane <tgl@sss.pgh.pa.us>
To: Cestmir Hybl <cestmirl@freeside.sk>
Cc: pgsql-performance@postgresql.org
Subject: Re: count(*) using index scan in "query often, update rarely" environment
Date: Fri, 07 Oct 2005 09:42:32 -0400
Message-ID: <3254.1128692552@sss.pgh.pa.us> (raw)
In-Reply-To: <935801c5cb20$dcf93a00$131fc39e@stratos>
References: <935801c5cb20$dcf93a00$131fc39e@stratos>
"Cestmir Hybl" <cestmirl@freeside.sk> writes:
> Isn't it possible (and reasonable) for these environments to keep track =
> of whether there is a transaction in progress with update to given table =
> and if not, use an index scan (count(*) where) or cached value =
> (count(*)) to perform this kind of query?
Please read the archives before bringing up such well-discussed issues.
There's a workable-looking design in the archives (pghackers probably)
for maintaining overall table counts in a separate table, with each
transaction adding one row of "delta" information just before it
commits. I haven't seen anything else that looks remotely attractive.
regards, tom lane
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To: pgsql-performance@postgresql.org
Cc: tgl@sss.pgh.pa.us, cestmirl@freeside.sk
Subject: Re: count(*) using index scan in "query often, update rarely" environment
In-Reply-To: <3254.1128692552@sss.pgh.pa.us>
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