On Fri, Mar 2, 2018 at 8:35 AM, Magnus Hagander <mag...@hagander.net> wrote: > Do we ever make hintbit changes on the standby for example? If so, it would > definitely cause problems. I didn't realize we did, actually...
We do not. > I guess we could get there even if we don't by: > * All checksums are correct > * Checkums are disabled (which replicates) > * Non-WAL logged change on the master, which updates checksum but does *not* > replicate > * Checksums re-enabled > * Worker sees the checksum as correct, and thus does not force a full page > write. > * Worker completes and flips checksums on which replicates. At this point, > if the replica reads the page, boom. Exactly. > I guess we have to remove that optimisation. It's definitely a bummer, but I > don't think it's an absolute dealbreaker. I don't disagree. > We could say that we keep the optimisation if wal_level=minimal for example, > because then we know there is no replica. But I doubt that's worth it? I don't have a strong feeling about this. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company
