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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 00:30:04
Message-ID: 25725.1043281804@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-performance
"Dann Corbit" <DCorbit(at)connx(dot)com> writes:
> For the disk case, why not have the start of the record contain an array
> of offsets to the start of the data for each column?  It would only be
> necessary to have a list for variable fields.

No, you'd need an entry for *every* column (or at least, every one to
the right of the first variable-width column or NULL).  That's a lot of
overhead, especially in comparison to datatypes like bool or int4 ...

			regards, tom lane

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