From: | Andres Freund <andres(at)anarazel(dot)de> |
---|---|
To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
Cc: | "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: multixacts woes |
Date: | 2015-05-08 18:41:32 |
Message-ID: | 20150508184132.GV12950@alap3.anarazel.de |
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Thread: | |
Lists: | pgsql-hackers |
On 2015-05-08 14:32:14 -0400, Robert Haas wrote:
> On Fri, May 8, 2015 at 2:27 PM, Andres Freund <andres(at)anarazel(dot)de> wrote:
> > On 2015-05-08 14:15:44 -0400, Robert Haas wrote:
> >> Apparently, we have been hanging our hat since the release of 9.3.0 on
> >> the theory that the average multixact won't ever have more than two
> >> members, and therefore the members SLRU won't overwrite itself and
> >> corrupt data.
> >
> > It's essentially a much older problem - it has essentially existed since
> > multixacts were introduced (8.1?). The consequences of it were much
> > lower before 9.3 though.
>
> OK, I wasn't aware of that. What exactly were the consequences before 9.3?
I think just problems when locking a row. That's obviously much less bad
than problems when reading a row.
> > FWIW, I intend to either work on this myself, or help whoever seriously
> > tackles this, in the next cycle.
>
> That would be great.
With "this" I mean freeze avoidance. While I obviously, having proposed
it as well at some point, think that freeze maps are a possible
solution, I'm not yet sure that it's the best solution.
> I'll investigate what resources EnterpriseDB can commit to this.
Cool.
Greetings,
Andres Freund
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