Re: Core team statement on replication in PostgreSQL

"Heikki Linnakangas" <heikki@enterprisedb.com> writes:
> Hmm, WAL version compatibility is an interesting question. Most minor 
> releases hasn't changed the WAL format, and it would be nice to allow 
> running different minor versions in the master and slave in those cases. 
> But it's certainly not unheard of to change the WAL format. Perhaps we 
> should introduce a WAL version number, similar to catalog version?

Yeah, perhaps.  In the past we've changed the WAL page ID field for
this; I'm not sure if that's enough or not.  It does seem like a good
idea to have a way to check that the slaves aren't trying to read a
WAL version they don't understand.  Also, it's possible that the WAL
format doesn't change across a major update, but you still couldn't
work with say an 8.4 master and an 8.3 slave, so maybe we need the
catalog version ID in there too.
        regards, tom lane