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Re: [HACKERS] Full page writes improvement, code update

From: "Zeugswetter Andreas ADI SD" <ZeugswetterA(at)spardat(dot)at>
To: "Koichi Suzuki" <suzuki(dot)koichi(at)oss(dot)ntt(dot)co(dot)jp>
Cc: "Hannu Krosing" <hannu(at)skype(dot)net>,"Joshua D(dot) Drake" <jd(at)commandprompt(dot)com>,"Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>,"Simon Riggs" <simon(at)2ndquadrant(dot)com>,<josh(at)agliodbs(dot)com>,<pgsql-hackers(at)postgresql(dot)org>,<pgsql-patches(at)postgresql(dot)org>
Subject: Re: [HACKERS] Full page writes improvement, code update
Date: 2007-04-23 15:37:38
Message-ID: E1539E0ED7043848906A8FF995BDA57901F3FF7A@m0143.s-mxs.net (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-patches
> I don't insist the name and the default of the GUC parameter. 
>  I'm afraid wal_fullpage_optimization = on (default) makes 
> some confusion because the default behavior becomes a bit 
> different on WAL itself.

Seems my wal_fullpage_optimization is not a good name if it caused
misinterpretation already :-(

> >> Amount of WAL after 60min. run of DBT-2 benchmark 
> >> wal_add_optimization_info = off (default) 3.13GB
> > 
> > how about wal_fullpage_optimization = on (default)

The meaning of wal_fullpage_optimization = on (default)
would be the same as your wal_add_optimization_info = off (default).
(Reversed name, reversed meaning of the boolean value)

It would be there to *turn off* the (default) WAL full_page
optimization.
For your pg_compresslog it would need to be set to off. 
"add_optimization_info" sounded like added info about/for some
optimization
which it is not. We turn off an optimization with the flag for the
benefit
of an easier pg_compresslog implementation.

As already said I would decouple this setting from the part that sets
the "removeable full page" flag in WAL, and making the recovery able to
skip dummy records. This I would do unconditionally.

Andreas

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