Hello,
At Thu, 26 Mar 2015 18:50:24 +0100, Andres Freund <andres@2ndquadrant.com> wrote in
<20150326175024.GJ451@alap3.anarazel.de>
> I think the problem here is that the *primary* makes no such
> assumptions. Init forks are logged via stuff like
> smgrwrite(index->rd_smgr, INIT_FORKNUM, BTREE_METAPAGE,
..
> i.e. the data is written out directly to disk, circumventing
> shared_buffers. It's pretty bad that we don't do the same on the
> standby. For master I think we should just add a bit to the XLOG_FPI
> record saying the data should be forced out to disk. I'm less sure
> what's to be done in the back branches. Flushing every HEAP_NEWPAGE
> record isn't really an option.
The problem exists only for INIT_FORKNUM. So I suppose it is
enough to check forknum to decide whether to sync immediately.
Specifically for this instance, syncing buffers of INIT_FORKNUM
at the end of XLOG_FPI block in xlog_redo fixed the problem.
The another (ugly!) solution sould be syncing only buffers for
INIT_FORKNUM and is BM_DIRTY in ResetUnlogggedRelations(op =
UNLOGGED_RELATION_INIT). This is catching-all-at-once solution
though it is a kind of reversion of fast promotion. But buffers
to be synced here should be pretty few.
regards,
--
Kyotaro Horiguchi
NTT Open Source Software Center
