Robert Haas pointed out in that thread that it has a problem with hint bits that are not WAL-logged,
I liked that tool a lot until Robert pointed out the above problem. I thought this is a show stopper because I can't really see any way to circumvent it unless we enable checksums or explicitly WAL log hint bits.
but it will still work if you also enable the new checksums feature, which forces hint bit updates to be WAL-logged.
Are we expecting a lot of people to run their clusters with checksums on ? Sorry, I haven't followed the checksum discussions and don't know how much overhead it causes. But if the general expectation is that checksums will be turned on most often, I agree pg_rewind is probably good enough.
Perhaps we could add a GUC to enable hint bits to be WAL-logged, regardless of checksums, to make pg_rewind work.
Wouldn't that be too costly ? I mean, in the worst case every hint bit on a page may get updated separately. If each such update is WAL logged, we are looking for a lot more unnecessary WAL traffic.
I think that's a more flexible approach to solve this problem. It doesn't require an online feedback loop from the standby to master, for starters.
I agree. That's a big advantage of pg_rewind. Unfortunately, it can't work with 9.3 and below because of the hint bits issue, otherwise it would have been even more cool.