From: Tom Lane <tgl@sss.pgh.pa.us>
To: molson@oceanconsulting.com
Cc: pgsql-performance@postgresql.org
Subject: Re: Prefetch
Date: Tue, 10 May 2005 10:16:20 -0400
Message-ID: <10061.1115734580@sss.pgh.pa.us> (raw)
In-Reply-To: <200505100652.51401.molson@oceanconsulting.com>
References: <200505100652.51401.molson@oceanconsulting.com>
Matt Olson <molson@oceanconsulting.com> writes:
> Other databases like Oracle and DB2 implement some sort of row prefetch. Has
> there been serious consideration of implementing something like a prefetch
> subsystem?
No.
> Does anyone have any opinions as to why this would be a bad idea for
> postgres?
We know even less than the OS does about disk layout, and not a lot more
than it about what our next request will be. (If we're doing a seqscan,
then of course that's not true, but I would expect the OS to be able to
figure that one out and do readahead.)
You haven't shown us your problem queries, but I think that conventional
query tuning would be a more appropriate answer. In particular I wonder
whether you shouldn't be looking at ways to calculate multiple
aggregates in parallel.
regards, tom lane
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To: pgsql-performance@postgresql.org
Cc: tgl@sss.pgh.pa.us, molson@oceanconsulting.com
Subject: Re: Prefetch
In-Reply-To: <10061.1115734580@sss.pgh.pa.us>
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