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From: Michael Paquier <michael@paquier.xyz>
To: Arthur Zakirov <a.zakirov@postgrespro.ru>
Cc: Grigory Smolkin <g.smolkin@postgrespro.ru>
Cc: pgsql-hackers@lists.postgresql.org
Subject: Re: [PATCH] xlogreader: do not read a file block twice
Date: Fri, 15 Feb 2019 08:06:16 +0900
Message-ID: <20190214230616.GA2240@paquier.xyz> (raw)
In-Reply-To: <7eaccd53-ea89-e0cf-b718-80e3f3fc3abf@postgrespro.ru>
References: <2ddf4a32-517e-d6f4-d992-4a63b6035bfd@postgrespro.ru>
	<87e30af6-f85a-dc95-4574-95cded028786@postgrespro.ru>
	<20190212042300.GL1475@paquier.xyz>
	<1fa0c9fe-32a5-3ebd-e9c2-b5e2c9abc03e@postgrespro.ru>
	<20190214065156.GE2366@paquier.xyz>
	<7eaccd53-ea89-e0cf-b718-80e3f3fc3abf@postgrespro.ru>

On Thu, Feb 14, 2019 at 11:20:56AM +0300, Arthur Zakirov wrote:
> So we read whole page with size XLOG_BLCKSZ. The full code:
> https://github.com/postgrespro/pg_probackup/blob/c052651b8c8864733bcabbc2660c387b792229d8/src/parsex...
> 
> Here is the little optimization I made. Mainly I just add a buffer to store
> previous read page:
> https://github.com/postgrespro/pg_probackup/blob/c052651b8c8864733bcabbc2660c387b792229d8/src/parsex...

Thanks, I see what you have done.  I cannot comment if your shortcut
is actually fully correct based on my knowledge of this code, but
things cannot be in the best conditions without having the WAL reader
handle properly the limits.  So I am planning to commit what you
propose after an extra pass on it in the next couple of days or so.
--
Michael

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  Subject: Re: [PATCH] xlogreader: do not read a file block twice
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