Re: Modifying TOAST_TUPLE_THRESHOLD and TOAST_TUPLE_TARGET?

From: Greg Stark <stark(at)enterprisedb(dot)com>
To: Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Shadar <shauldar(at)gmail(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: Modifying TOAST_TUPLE_THRESHOLD and TOAST_TUPLE_TARGET?
Date: 2009-06-11 15:41:22
Message-ID: 4136ffa0906110841w1e9f12b9u79a401f82a1c17d9@mail.gmail.com
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On Thu, Jun 11, 2009 at 4:24 PM, Kevin
Grittner<Kevin(dot)Grittner(at)wicourts(dot)gov> wrote:
>
> I thought that's the behavior of EXTENDED.  The fine manual says "MAIN
> allows compression but not out-of-line storage. (Actually, out-of-line
> storage will still be performed for such columns, but only as a last
> resort when there is no other way to make the row small enough.)"
>
> If that doesn't mean that it will only use out-of-line storage when
> the row doesn't fit in the page, then the manual could use a fix.

I agree that "small enough" could be more precise. As it happens
tuptoaster.c only has one definition of "small enough" which is
whether the record is smaller than TOAST_TUPLE_THRESHOLD.

I wonder actually if this case shouldn't use the block size, not the
target size. That seems like it would be a lot more useful.

--
Gregory Stark
http://mit.edu/~gsstark/resume.pdf

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