Re: pgsql: Avoid duplicate XIDs at recovery when building initial snapshot

From: Michael Paquier <michael(at)paquier(dot)xyz>
To: Simon Riggs <simon(at)2ndquadrant(dot)com>
Cc: Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: pgsql: Avoid duplicate XIDs at recovery when building initial snapshot
Date: 2018-12-03 06:43:58
Message-ID: 20181203064358.GI3423@paquier.xyz
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On Sat, Dec 01, 2018 at 10:51:10AM +0000, Simon Riggs wrote:
> On Fri, 30 Nov 2018 at 23:08, Michael Paquier <michael(at)paquier(dot)xyz> wrote:
>> It is not complicated to
>> handle duplicates for xacts and subxacts however holding ProcArrayLock
>> for a longer time stresses me as it is already a bottleneck.
>
> I hadn't realised this patch holds ProcArrayLock while removing duplicates.
> Now I know I vote against applying this patch unless someone can show that
> the performance effects of doing so are negligable, which I doubt.

Me too after more thoughts on that. Please note that I have marked the
patch as returned with feedback for now.
--
Michael

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