From: Tom Lane <tgl@sss.pgh.pa.us>
To: Bruce Momjian <bruce@momjian.us>
Cc: Matthew Wakeling <matthew@flymine.org>
Cc: pgsql-performance@postgresql.org
Subject: Re: I/O on select count(*)
Date: Mon, 19 May 2008 11:37:58 -0400
Message-ID: <5697.1211211478@sss.pgh.pa.us> (raw)
In-Reply-To: <200805191454.m4JEs6400890@momjian.us>
References: <200805191454.m4JEs6400890@momjian.us>
Bruce Momjian <bruce@momjian.us> writes:
> Matthew Wakeling wrote:
>> Does it really take that long to zero out 8kB of RAM? I thought CPUs were
>> really quick at doing that!
> Yea, that was my assumption too.
You have to write the page (to be sure there is space for it on disk)
not only zero it.
This design is kind of a holdover, though, from back when we had one
ever-growing clog file. Today I'd be inclined to think about managing
it more like pg_xlog, ie, have some background process pre-create a
whole segment file at a time.
regards, tom lane
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To: pgsql-performance@postgresql.org
Cc: tgl@sss.pgh.pa.us, bruce@momjian.us, matthew@flymine.org
Subject: Re: I/O on select count(*)
In-Reply-To: <5697.1211211478@sss.pgh.pa.us>
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