Date: Wed, 10 Jan 2018 10:24:10 +0900
From: Michael Paquier <michael.paquier@gmail.com>
To: Claudio Freire <klaussfreire@gmail.com>
Cc: Rambabu V <ram.wissen@gmail.com>,
	postgres performance list <pgsql-performance@postgresql.org>
Subject: Re: Need Help on wal_compression
Message-ID: <20180110012410.GD336@paquier.xyz>
References: 
 <CADtiZxp0ksqNsM=uomMehcZafxWP+nvTyCCbT4Ejy9A_6GD6Fg@mail.gmail.com>
 <CAGTBQpZcbQjj-wHjgUCGOTSC5jhY+aOMa-Eom-31jNt4GJcADg@mail.gmail.com>
MIME-Version: 1.0
Content-Type: multipart/signed; micalg=pgp-sha256;
	protocol="application/pgp-signature"; boundary="IDYEmSnFhs3mNXr+"
Content-Disposition: inline
In-Reply-To: 
 <CAGTBQpZcbQjj-wHjgUCGOTSC5jhY+aOMa-Eom-31jNt4GJcADg@mail.gmail.com>
Precedence: bulk


--IDYEmSnFhs3mNXr+
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline

On Tue, Jan 09, 2018 at 01:53:14PM -0300, Claudio Freire wrote:
> That shows 50% of that are full page writes. This is with compression
> enabled. WAL compression will only help FPW, so if you don't have a large
> volume of FPW, or they don't compress well, you won't benefit much.

This highly depends on the data types used as well. You won't get much
compressibility with things like UUIDs for example. When we worked on
the patch, I recall that FDW compression saved 25% for a relation with a
one-column integer, and only 12~15% when using UUIDs.
--
Michael

--IDYEmSnFhs3mNXr+
Content-Type: application/pgp-signature; name="signature.asc"

-----BEGIN PGP SIGNATURE-----
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=ik97
-----END PGP SIGNATURE-----

--IDYEmSnFhs3mNXr+--