FWIW.. At Thu, 06 Jul 2017 18:54:47 +0900 (Tokyo Standard Time), Kyotaro HORIGUCHI <horiguchi.kyot...@lab.ntt.co.jp> wrote in <20170706.185447.256482539.horiguchi.kyot...@lab.ntt.co.jp> > > > + /* > > > + * Force the on-disk state of init forks to always be in sync > > > with the > > > + * state in shared buffers. See XLogReadBufferForRedoExtended. > > > + */ > > > + XLogRecGetBlockTag(record, 0, NULL, &forknum, NULL); > > > + if (forknum == INIT_FORKNUM) > > > + FlushOneBuffer(metabuf); > > > I find those forced syncs a bit surprising. The buffer is already > > > marked as dirty, so even if there is a concurrent checkpoint they > > > would be flushed. > > > > > > > What if there is no concurrent checkpoint activity and the server is > > shutdown? Remember this replay happens on standby and we will just > > try to perform Restartpoint and there is no guarantee that it will > > flush the buffers. If the buffers are not flushed at shutdown, then > > the Init fork will be empty on restart and the hash index will be > > corrupt. > > XLogReadBufferForRedoExtended() automatically force the flush for > a XLOG record on init fork that having FPW imaeges. And > _hash_init seems to have emitted such a XLOG record using > log_newpage. > > > > If recovery comes again here, then they would just > > > be replayed. I am unclear why XLogReadBufferForRedoExtended is not > > > enough to replay a FPW of that. > > > > > > > Where does FPW come into the picture for a replay of metapage or bitmappage? > > Since required FPW seems to be emitted and the flush should be > done automatically, the issuer side (_hash_init) may attach wrong
"may attach" -> "may have attached" > FPW images if hash_xlog_init_meta_page requires additional > flushes. But I don't see such a flaw there. I think Michael wants > to say such a kind of thing. regards. -- Kyotaro Horiguchi NTT Open Source Software Center -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
