From: | Jeff Janes <jeff(dot)janes(at)gmail(dot)com> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | Claudio Freire <klaussfreire(at)gmail(dot)com>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Abhijit Menon-Sen <ams(at)2ndquadrant(dot)com>, PostgreSQL-Dev <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: allowing VACUUM to be cancelled for conflicting locks |
Date: | 2014-04-28 18:03:53 |
Message-ID: | CAMkU=1ysr2hjcRBuoH4BS=8fm-50Xey4kuuOSzPpFXpekSh7kA@mail.gmail.com |
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Lists: | pgsql-hackers |
On Mon, Apr 28, 2014 at 10:58 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Claudio Freire <klaussfreire(at)gmail(dot)com> writes:
> > On Mon, Apr 28, 2014 at 12:52 PM, Alvaro Herrera
> > <alvherre(at)2ndquadrant(dot)com> wrote:
> >> Tom Lane wrote:
> >>> Abhijit Menon-Sen <ams(at)2ndquadrant(dot)com> writes:
> >>>> In the past, we've had situations where "everything is hung" turned
> out
> >>>> to be because of a script that ran manual VACUUM that was holding some
> >>>> lock. It's admittedly not a huge problem, but it might be useful if a
> >>>> manual VACUUM could be cancelled the way autovacuum can be.
>
> >>> I think the real answer to that is "stop using manual VACUUM".
>
> >> As much as I'm a fan of autovacuum, that's not always possible.
>
> > Or even recommended, unless the docs changed radically in the last
> > couple of weeks.
>
> Actually, having just looked at the code in question, I think this whole
> thread is based on an obsolete assumption. AFAICS, since commit b19e4250b
> manual vacuum behaves exactly like autovacuum as far as getting kicked off
> the exclusive lock is concerned. There's certainly not any tests for
> autovacuum in lazy_truncate_heap() today.
>
I assumed he was a talking about the SHARE UPDATE EXCLUSIVE used during the
main work, not the ACCESS EXCLUSIVE one used during truncation.
Cheers,
Jeff
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