From: | Andres Freund <andres(at)anarazel(dot)de> |
---|---|
To: | Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> |
Cc: | "Wood, Dan" <hexpert(at)amazon(dot)com>, Peter Geoghegan <pg(at)bowt(dot)ie>, pgsql-committers(at)postgresql(dot)org, "Wong, Yi Wen" <yiwong(at)amazon(dot)com>, Michael Paquier <michael(dot)paquier(at)gmail(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: [HACKERS] [COMMITTERS] pgsql: Fix freezing of a dead HOT-updated tuple |
Date: | 2017-11-14 04:07:01 |
Message-ID: | 20171114040701.xu4ew2slpkl6tmct@alap3.anarazel.de |
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On 2017-11-13 19:03:41 -0800, Andres Freund wrote:
> Hi,
>
> On 2017-11-03 07:53:30 -0700, Andres Freund wrote:
> > Here's that patch. I've stared at this some, and Robert did too. Robert
> > mentioned that the commit message might need some polish and I'm not
> > 100% sure about the error message texts yet.
> >
> > I'm not yet convinced that the new elog in vacuumlazy can never trigger
> > - but I also don't think we want to actually freeze the tuple in that
> > case.
>
> I'm fairly sure it could be triggered, therefore I've rewritten that.
>
> I've played around quite some with the attached patch. So far, after
> applying the second patch, neither VACUUM nor VACUUM FULL / CLUSTER make
> the situation worse for already existing corruption. HOT pruning can
> change the exact appearance of existing corruption a bit, but I don't
> think it can make the corruption meaningfully worse. It's a bit
> annoying and scary to add so many checks to backbranches but it kinda
> seems required. The error message texts aren't perfect, but these are
> "should never be hit" type elog()s so I'm not too worried about that.
>
>
> Please review!
Please note:
I'd forgotten to git add the change to isolation_schedule re-activating
the freeze-the-dead regression test.
- Andres
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