Re: [HACKERS] [COMMITTERS] pgsql: Fix freezing of a dead HOT-updated tuple

On 2017-11-20 11:18:45 -0800, Andres Freund wrote:
> Hi,
>
> 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!
>
> Ping? Alvaro, it'd be good to get some input here.

Ping. I'm a bit surprised that a bug fixing a significant data
corruption issue has gotten no reviews at all.

Greetings,

Andres Freund