On Wed, Dec 4, 2013 at 8:43 PM, Tom Lane <t...@sss.pgh.pa.us> wrote: > Magnus Hagander <mag...@hagander.net> writes: > > On Tue, Dec 3, 2013 at 7:20 PM, Tom Lane <t...@sss.pgh.pa.us> wrote: > >> I assume what would happen is the slave would PANIC upon seeing a WAL > >> record code it didn't recognize. > > > I wonder if we should for the future have the START_REPLICATION command > (or > > the IDENTIFY_SYSTEM would probably make more sense - or even adding a new > > command like IDENTIFY_CLIENT. The point is, something in the replication > > protocol) have walreceiver include it's version sent to the master. That > > way we could have the walsender identify a walreceiver that's too old and > > disconnect it right away - with a much nicer error message than a PANIC. > > Meh. That only helps for the case of streaming replication, and not for > the thirty-seven other ways that some WAL might arrive at something that > wants to replay it. > > It might be worth doing anyway, but I can't get excited about it for this > scenario. >
It does, but I bet it's one of the by far most common cases. I'd say it's that one and restore-from-backup that would cover a huge majority of all cases. If we can cover those, we don't have to be perfect - so unless it turns out to be ridiculously complicated, I think it would be worthwhile having. -- Magnus Hagander Me: http://www.hagander.net/ Work: http://www.redpill-linpro.com/
