On 2013-09-05 14:37:01 -0400, Tom Lane wrote: > Andres Freund <and...@2ndquadrant.com> writes: > > On 2013-09-05 14:21:33 -0400, Tom Lane wrote: > >> Ideally I'd have made InvalidCommandId = 0 and FirstCommandId = 1, > >> but I suppose we can't have that without an on-disk compatibility break. > > > The patch actually does change it exactly that way. > > Oh. I hadn't looked at the patch, but I had (mis)read what Robert said > to think that you were proposing introducing InvalidCommandId = 0xFFFFFFFF > while leaving FirstCommandId alone. That would make more sense to me as > (1) it doesn't change the interpretation of anything that's (likely to be) > on disk; (2) it allows the check for overflow in CommandCounterIncrement > to not involve recovering from an *actual* overflow. With the horsing > around we've been seeing from the gcc boys lately
Ok, I can do it that way. LCR obviously shouldn't care. > I don't have a warm > feeling about whether they won't break that test someday on the grounds > that "overflow is undefined behavior". Unsigned overflow is pretty strictly defined, so I don't see much danger there. Also, we'd feel the pain pretty definitely with xids... 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
