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

Hi,

Zeugswetter Andreas ADI SD wrote:
>> 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.

For pg_compresslog to remove full page writes, we need
wal_add_optimization_info=on.

>
> 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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--
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Koichi Suzuki