| From: | Michael Paquier <michael(dot)paquier(at)gmail(dot)com> |
|---|---|
| To: | Chapman Flack <chap(at)anastigmatix(dot)net> |
| Cc: | Heikki Linnakangas <hlinnaka(at)iki(dot)fi>, Robert Haas <robertmhaas(at)gmail(dot)com>, Bruce Momjian <bruce(at)momjian(dot)us>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: AdvanceXLInsertBuffer vs. WAL segment compressibility |
| Date: | 2017-07-17 15:00:02 |
| Message-ID: | CAB7nPqSGYEngZuUU8fmeFo5c3hcYFpPKwO12mU1yngwDC=KS9A@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Fri, Jun 23, 2017 at 6:08 AM, Chapman Flack <chap(at)anastigmatix(dot)net> wrote:
> Well, gzip was doing pretty well; it could get a 16 MB segment file down
> to under 27 kB, or less than 14 bytes for each of 2000 pages, when a page
> header is what, 20 bytes, it looks like? I'm not sure how much better
> I'd expect a (non-custom) compression scheme to do. The real difference
> comes between compressing (even well) a large unchanged area, versus being
> able to recognize (again with a non-custom tool) that the whole area is
> unchanged.
Have you tried as well lz4 for your cases? It performs faster than
gzip at minimum compression and compresses less, but I am really
wondering if for almost zero pages it performs actually better.
--
Michael
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