Re: [HACKERS] GSoC 2017: weekly progress reports (week 6)

From: Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>
To: Teodor Sigaev <teodor(at)sigaev(dot)ru>
Cc: Dmitry Ivanov <d(dot)ivanov(at)postgrespro(dot)ru>, Shubham Barai <shubhambaraiss(at)gmail(dot)com>, Alexander Korotkov <a(dot)korotkov(at)postgrespro(dot)ru>, Andrey Borodin <x4mmm(at)yandex-team(dot)ru>, Thomas Munro <thomas(dot)munro(at)enterprisedb(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>, Andrew Borodin <amborodin86(at)gmail(dot)com>, Kevin Grittner <kgrittn(at)gmail(dot)com>
Subject: Re: [HACKERS] GSoC 2017: weekly progress reports (week 6)
Date: 2018-03-29 17:24:46
Message-ID: 20180329172446.jzddgkntzdke6cez@alvherre.pgsql
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Teodor Sigaev wrote:
>
> Alvaro Herrera wrote:
> > I don't quite understand the new call in gininsert -- I mean I see that
> > it wants to check for conflicts even when fastupdate is set, but why?
> If fastupdate is set then we check conflict with whole index, not a
> particular pages in it. Predicate lock on penging list pages will be
> effectively a lock over index, because every scan will begin from pending
> list and each insert will insert into it. I

Oh, right, that makes sense. I'm not sure that the comments explain
this sufficiently -- I think it'd be good to expand that.

Given this patch, it seems clear that serializable mode is much worse
with fastupdate than without it!

--
Álvaro Herrera https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

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