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

From: Teodor Sigaev <teodor(at)sigaev(dot)ru>
To: Shubham Barai <shubhambaraiss(at)gmail(dot)com>, Alexander Korotkov <a(dot)korotkov(at)postgrespro(dot)ru>
Cc: Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>, 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: 2018-03-23 11:27:14
Message-ID: 2667bf88-958b-e51f-140b-b6ea3e6424e9@sigaev.ru
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Hi!

Patch seems good, but I found one bug in it, in fact, nobody
checks serializible conflict with fastupdate=on:
gininsert()
{
if (GinGetUseFastUpdate())
{
/* two next lines are GinCheckForSerializableConflictIn() */
if (!GinGetUseFastUpdate())
CheckForSerializableConflictIn()
}
}

I changed to direct call CheckForSerializableConflictIn() (see attachment)

I'd like to see fastupdate=on in test too, now tests cover only case without
fastupdate. Please, add them.

Shubham Barai wrote:
>
>
> On 16 March 2018 at 03:57, Alexander Korotkov <a(dot)korotkov(at)postgrespro(dot)ru
> <mailto:a(dot)korotkov(at)postgrespro(dot)ru>> wrote:
>
> On Tue, Mar 13, 2018 at 3:25 PM, Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org
> <mailto:alvherre(at)alvh(dot)no-ip(dot)org>> wrote:
>
> Alexander Korotkov wrote:
>
> > And what happen if somebody concurrently set (fastupdate = on)?
> > Can we miss conflicts because of that?
>
> I think it'd be better to have that option require AccessExclusive lock,
> so that it can never be changed concurrently with readers.  Seems to me
> that penalizing every single read to cope with this case would be a bad
> trade-off.
>
>
> As Andrey Borodin mentioned, we already do.  Sorry for buzz :)
>
>
>
> I have updated the patch based on suggestions.
>
> Regards,
> Shubham

--
Teodor Sigaev E-mail: teodor(at)sigaev(dot)ru
WWW: http://www.sigaev.ru/

Attachment Content-Type Size
Predicate-Locking-in-gin-index_v7.patch text/x-patch 47.1 KB

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