On Monday, September 17, 2012 04:59:06 PM Robert Haas wrote: > On Sun, Sep 16, 2012 at 2:54 PM, Simon Riggs <si...@2ndquadrant.com> wrote: > > Fix bufmgr so CHECKPOINT_END_OF_RECOVERY behaves as a shutdown > > checkpoint. Recovery code documents clearly that a shutdown checkpoint > > is executed at end of recovery - a shutdown checkpoint WAL record is > > written but the buffer manager had been altered to treat end of recovery > > as a normal checkpoint. This bug exacerbates the bufmgr relpersistence > > bug. > > > > Bug spotted by Andres Freund, patch by me. > > I am confused by this patch. It seems to me that the effect of this > patch is to force unlogged buffers to be written at end-of-recovery as > well as at shutdown. But, barring bugs elsewhere, there shouldn't be > any unlogged buffers in shared_buffers at end-of-recovery, so this > won't make any difference at all. Am I missing something? I just noted during investigating of the impact of the fakerelcache bug that contrary to whats claimed at several places END_OF_RECOVERY checkpoints do *not* behave the same way CHECKPOINT_IS_SHUTDOWN ones do. Which doesn't seem to be a good idea. E.g. the impact of this bug would have been smaller if they were really treated the same. Unless I missed something thats the only place of relevance that treats them differently. Imo treating them different in some remote places (2 calls away) is a good way to introduce further bugs.
> Maybe what we should do is - if this is an end-of-recovery checkpoint > - *assert* that the BM_PERMANENT bit is set on every buffer we find. > That would provide a useful cross-check that we don't have a bug > similar to the one Jeff already fixed in any other code path. I haven't looked into the details, but can't a new unlogged relation be created since the last checkpoint and thus have pages in s_b? Greetings, Andres -- Andres Freund http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
