On 2013-10-21 14:22:17 -0400, Robert Haas wrote: > On Mon, Oct 21, 2013 at 1:52 PM, Andres Freund <and...@2ndquadrant.com> wrote: > >> > In my opinion, (4) is too ugly to consider. I think that if we start > >> > playing games like this, we're opening up the doors to lots of subtle > >> > bugs and future architectural pain that will be with us for many, many > >> > years to come. I believe we will bitterly regret any foray into this > >> > area. > >> > >> Hm. After looking at the required code - which you obviously cannot have > >> yet - it's not actually too bad. Will post a patch implementing it later. > >> > >> I don't really buy the architectural argument since originally cmin/cmax > >> *were* both stored. It's not something we're just inventing now. We just > >> optimized that away but now have discovered that's not always a good > >> idea and thus don't always use the optimization. > >> > >> The actual decoding code shrinks by about 200 lines using this logic > >> which is a hint that it's not a bad idea. > > > > So, here's a preliminary patch to see how this would look. It'd be great > > of you comment if you still think it's a completel no-go. > > > > If it were for real, it'd need to be split and some minor things would > > need to get adjusted, but I think it's easier to review it seing both > > sides at once. > > I think it's a complete no-go. Consider, e.g., the comment for > MaxTupleAttributeNumber, which you've blithely falsified. Even if you > update the comment and the value, I'm not inspired by the idea of > subtracting 32 from that number; even if it weren't already too small, > it would break pg_upgrade for any users who are on the edge.
Well, we only need to support it for (user_)catalog tables. So pg_upgrade isn't a problem. And I don't really see a problem restricting the number of columns for such tables. > Things > aren't looking too good for anything that uses HeapTupleFields, > either; consider rewrite_heap_tuple(). Well, that currently works, by copying cmax. Since rewriting triggered the change, I am pretty sure I've actually tested & hit that path... Greetings, Andres Freund -- Andres Freund http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
