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Re: [GENERAL] TOAST not working

From: "Jim C(dot) Nasby" <jnasby(at)pervasive(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Christopher Browne <cbbrowne(at)acm(dot)org>, pgsql-docs(at)postgresql(dot)org
Subject: Re: [GENERAL] TOAST not working
Date: 2006-06-11 03:15:14
Message-ID: 20060611031514.GB34196@pervasive.com (view raw or flat)
Thread:
Lists: pgsql-docspgsql-general
Dropping -general

On Sat, Jun 10, 2006 at 10:58:49PM -0400, Tom Lane wrote:
> "Jim C. Nasby" <jnasby(at)pervasive(dot)com> writes:
> > Actually, it's BLCKSZ/4. From
> > http://www.postgresql.org/docs/8.1/interactive/storage-toast.html:
> 
> > "The TOAST code is triggered only when a row value to be stored in a
> > table is wider than BLCKSZ/4 bytes (normally 2Kb)."
> 
> > BTW, 'row value' seems a bit prone to confusion (could be interpreted as
> > the row itself). It'd probably be better to say 'field'.
> 
> No, because that would be wrong; the statement is correct as written.
> The toaster tries to do something about rows that are wider than
> BLCKSZ/4 (well, actually MaxTupleSize/4 ... try grepping the source
> for TOAST_TUPLE_THRESHOLD).
 
I'll argue that the docs are still confusing though, since 'row value'
could be interpreted as 'field', especially since the first paragraph
contains "In release 7.1 and later, this limit is overcome by allowing
large field values to be compressed and/or broken up into multiple
physical rows."
-- 
Jim C. Nasby, Sr. Engineering Consultant      jnasby(at)pervasive(dot)com
Pervasive Software      http://pervasive.com    work: 512-231-6117
vcard: http://jim.nasby.net/pervasive.vcf       cell: 512-569-9461

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