> > Hm. If GetOldestMultiXactOnDisk() gets the starting point by scanning > > the disk it'll always get one at a segment boundary, right? I'm not sure > > that's actually ok; because the value at the beginning of the segment > > can very well end up being a 0, as MaybeExtendOffsetSlru() will have > > filled the page with zeros. > > > > I think that should be harmless, the worst that can happen is that > > oldestOffset errorneously is 0, which should be correct, even though > > possibly overly conservative, in these cases. > > Uh oh. That seems like a real bad problem for this approach. What > keeps that from being the opposite of too conservative? There's no > "safe" value in a circular numbering space.
I think it *might* (I'm really jetlagged) be fine because that'll only happen after a upgrade from < 9.3. And in that case we initialize nextOffset to 0. That ought to safe us? Greetings, Andres Freund -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
