Re: [Solved] SQL Server to PostgreSQL

From: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: adam(dot)rossi(at)platinumsolutions(dot)com, Jan Wieck <janwieck(at)Yahoo(dot)com>, Martin Christensen <knightsofspamalot-factotum(at)mail1(dot)stofanet(dot)dk>, "pgsql-general(at)postgresql(dot)org" <pgsql-general(at)postgresql(dot)org>
Subject: Re: [Solved] SQL Server to PostgreSQL
Date: 2000-10-15 03:28:12
Message-ID: 200010150328.XAA22369@candle.pha.pa.us
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> Ian Turner <vectro(at)pipeline(dot)com> writes:
> > Don't variable-length records incur a performance overhead?
>
> Only to the extent that the system can't cache offset information for
> later columns in that table. While someone evidently once thought that
> was worthwhile, I've never seen the column-access code show up as a
> particularly hot spot in any profile I've run. I doubt you could
> actually measure any difference, let alone show it to be important
> enough to be worth worrying about.

It clearly is a hot-spot. That monster macro, fastgetattr(), in
heapam.h is in there for a reason. It accounts for about 5% for straight
sequential scan case, last I heard from someone who ran a test.

--
Bruce Momjian | http://candle.pha.pa.us
pgman(at)candle(dot)pha(dot)pa(dot)us | (610) 853-3000
+ If your life is a hard drive, | 830 Blythe Avenue
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