On Wed, Sep 4, 2013 at 12:07 PM, Andres Freund <and...@2ndquadrant.com> wrote: > On 2013-09-03 11:40:57 -0400, Robert Haas wrote: >> > 0002 wal_decoding: Introduce InvalidCommandId and declare that to be the >> > new maximum for CommandCounterIncrement >> >> I'm still unconvinced we want this. > > Ok, so the reason for the existance of this patch is that currently > there is no way to represent a "unset" CommandId. This is a problem for > the following patches because we need to log the cmin, cmax of catalog > rows and obviously there can be rows where cmax is unset.
For heap tuples, we solve this problem by using flag bits. Why not adopt the same approach? > The reason I chose to change the definition of CommandIds is that the > other ondisk types we use like TransactionIds, XLogRecPtrs and such have > an "invalid" type, CommandIds don't. Changing their definition to have 0 > - analogous to the previous examples - as their invalid value is not a > problem because CommandIds from pg_upgraded clusters may never be used > for anything. Going from 2^32 to 2^32-1 possible CommandIds doesn't seem > like a problem to me. Imo the CommandIds should have been defined that > way from the start. > > Makes some sense? I don't have a problem with this if other people think it's a good idea. But I think it needs a few +1s and not too many -1s first, and so far (AFAIK) no one else has weighed in with an opinion. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
