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From: Petr Jelinek <petr@2ndquadrant.com>
To: Andres Freund <andres@anarazel.de>
Cc: Tomas Vondra <tomas.vondra@2ndquadrant.com>
Cc: Andrey Borodin <x4mmm@yandex-team.ru>
Cc: Konstantin Knizhnik <k.knizhnik@postgrespro.ru>
Cc: Michael Paquier <michael@paquier.xyz>
Cc: pgsql-hackers <pgsql-hackers@postgresql.org>
Cc: Vladimir Leskov <vladimirlesk@yandex-team.ru>
Subject: Re: pglz performance
Date: Mon, 5 Aug 2019 00:19:28 +0200
Message-ID: <dc736f7e-7b32-cb41-853c-0b0c46bef9f3@2ndquadrant.com> (raw)
In-Reply-To: <20190804221533.3lpbs5krfnjisflj@alap3.anarazel.de>
References: <DBB2A9E5-29FD-40BF-AC60-BD990FBF142F@yandex-team.ru>
	<20190802163948.i6mjypdgujeorrbi@alap3.anarazel.de>
	<20190802170039.o4pabnzm4xy3z7uj@development>
	<20190802171258.nob5zo2vu7siqo2b@alap3.anarazel.de>
	<20190802175239.5ds6rhdso6hwy4vk@development>
	<20190802182003.u477q6itwudieqxf@alap3.anarazel.de>
	<20190802194859.qxzxq2achzottkup@development>
	<d8576096-76ba-487d-515b-44fdedba8bb5@2ndquadrant.com>
	<20190804115237.nliwf6hhaqfd62ps@development>
	<a5cbd707-e4a4-70e7-e970-75f1cc68c20f@2ndquadrant.com>
	<20190804221533.3lpbs5krfnjisflj@alap3.anarazel.de>

Hi,

On 05/08/2019 00:15, Andres Freund wrote:
> Hi,
> 
> On 2019-08-04 17:53:26 +0200, Petr Jelinek wrote:
>>> 5) I wonder why compression_algorithm is defined as PGC_SIGHUP. Why not
>>> to allow users to set it per session? I suppose we might have a separate
>>> option for WAL compression_algorithm.
>>>
>>
>> Yeah I was thinking we might want to change wal_compression to enum as well.
>> Although that complicates the code quite a bit (the caller has to decide
>> algorithm instead compression system doing it).
> 
> Isn't that basically required anyway? The WAL record will need to carry
> information about the type of compression used, independent of
> PGC_SIGHUP/PGC_USERSET, unless you want to make it an initdb option or
> something super heavyweight like that.
> 

It carries that information inside the compressed value, like I said in 
the other reply, that's why the extra byte.

-- 
Petr Jelinek
2ndQuadrant - PostgreSQL Solutions for the Enterprise
https://www.2ndQuadrant.com/





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