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Re: Higher TOAST compression.

From: "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov>
To: "Laurent Laborde" <kerdezixe(at)gmail(dot)com>, "PostgreSQL-development" <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Higher TOAST compression.
Date: 2009-07-17 17:50:51
Message-ID: 4A6073AB0200002500028939@gw.wicourts.gov (view raw or flat)
Thread:
Lists: pgsql-hackers
Laurent Laborde <kerdezixe(at)gmail(dot)com> wrote: 
 
> What about trying to change the TOAST_TUPLE_TARGET to get a higher
> compression (by having more toasted record) ?
> 
> I'd like to change the TOAST_TUPLES_PER_PAGE. Maybe from 4 to 8 ?
> Is that correct ? Did i missed something ?
> 
> I did some statistics and i will have much more TOASTed record as
> most of them are between 1KB and 2KB.
 
It seems like it might be reasonable to have a separate threshold for
compression from that for out-of-line storage.  Since I've been in
that code recently, I would be pretty comfortable doing something
about that; but, as is so often the case, the problem will probably be
getting agreement on what would be a good change.
 
Ignoring for a moment the fact that "low hanging fruit" in the form of
*very* large values can be handled first, the options would seem to
be:
 
(1)  Just hard-code a lower default threshold for compression than for
out-of-line storage.
 
(2)  Add a GUC or two to control thresholds.
 
(3)  Allow override of the thresholds for individual columns.
 
Are any of these non-controversial?  What do people like there?  What
did I miss?
 
-Kevin

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