Re: Higher TOAST compression.

My 1st applied patch is the safest and simpliest :
in pg_lzcompress.c :

static const PGLZ_Strategy strategy_default_data = {
256, /* Data chunks less than 256 are not compressed */
256, /* force compression on data chunks on record >= 256bytes */
1, /* compression rate below 1% fall back to uncompressed */
256, /* Stop history lookup if a match of 256 bytes is found */
6 /* lower good match size b 6% at every lookup iteration */
};
const PGLZ_Strategy *const PGLZ_strategy_default = &strategy_default_data;

I need to test for a few days. But the firsts tests show that we're
still IObound :)
The most obvious effect is reduction by a factor 2~10 of the size of
some TOAST table.
It seems that a lot of record are now kept in-line instead of being
stored in TOAST.

I will come back later with some numbers :)

Next patch will be a modified kevin's patch. (it doesn't directly
apply to our source code as i'm using postgresql 8.3 and his patch is
for 8.4) and a change in TOAST thresold and target.

What do you think about the parameters i used in the compression strategy ?
PS : biggest records are french text and html. (blog data : articles,
comments, ...)
Thank you.

--
Laurent Laborde
Sysadmin @ http://www.over-blog.com/