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Re: Terrible performance on wide selects

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: "Dann Corbit" <DCorbit(at)connx(dot)com>
Cc: "Steve Crawford" <scrawford(at)pinpointresearch(dot)com>,pgsql-performance(at)postgreSQL(dot)org, pgsql-hackers(at)postgreSQL(dot)org
Subject: Re: Terrible performance on wide selects
Date: 2003-01-23 00:04:02
Message-ID: 25521.1043280242@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-performance
"Dann Corbit" <DCorbit(at)connx(dot)com> writes:
> Maybe I don't really understand the problem, but it seems simple enough
> to do it once for the whole query.

We already do cache column offsets when they are fixed.  The code that's
the problem executes when there's a variable-width column in the table
--- which means that all columns to its right are not at fixed offsets,
and have to be scanned for separately in each tuple, AFAICS.

			regards, tom lane

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