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Re: planner/optimizer question

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: josh(at)agliodbs(dot)com
Cc: "Gary Doades" <gpd(at)gpdnet(dot)co(dot)uk>,pgsql-performance(at)postgresql(dot)org
Subject: Re: planner/optimizer question
Date: 2004-04-29 23:17:49
Message-ID: 17898.1083280669@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-performance
Josh Berkus <josh(at)agliodbs(dot)com> writes:
> Certainly the fact that MSSQL is essentially a single-user database makes 
> things easier for them.

Our recent testing (cf the "Xeon" thread) says that the interlocking we
do to make the world safe for multiple backends has a fairly high cost
(at least on some hardware) compared to the rest of the work in
scenarios where you are doing zero-I/O scans of data already in memory.
Especially so for index scans.  I'm not sure this completely explains
the differential that Gary is complaining about, but it could be part of
it.  Is it really true that MSSQL doesn't support concurrent operations?

			regards, tom lane

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