On Fri, Apr 23, 2010 at 4:44 PM, Tom Lane <t...@sss.pgh.pa.us> wrote: > Simon Riggs <si...@2ndquadrant.com> writes: >> No intention of doing that. This change allows people to see what the >> dependency actually is once the bug has been fixed. Change needs to >> start from here, not from where we were before. > > Well, actually, now that I've looked at the patch I think it's starting > from a fundamentally wrong position anyway. Checkpoint records are a > completely wrong mechanism for transmitting this data to slaves, because > a checkpoint is emitted *after* we do something, not *before* we do it. > In particular it's ludicrous to be looking at shutdown checkpoints to > try to determine whether the subsequent WAL will meet the slave's > requirements. There's no connection at all between what the GUC state > was at shutdown and what it might be after starting again. > > A design that might work is > (1) store the active value of wal_mode in pg_control (but NOT as part of > the last-checkpoint-record image). > (2) invent a new WAL record type that is transmitted when we change > wal_mode.
Well, right now wal_mode would only be able to be changed at server restart. Eventually we might relax that, but I think there are some restrictions on how we can do it - like maybe needing to wait until all the transactions running at the time the change was decided on have committed, or, well, I'm not sure. ...Robert -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
