Greg Stark <stark@mit.edu> writes:
> On Fri, Jun 14, 2013 at 2:21 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> So it's not that we actually need to log the individual hint bit
>> changes, it's that we need to WAL-log a full page image on the first
>> update after a checkpoint, so as to recover from torn-page cases.
>> Which one are we doing?
> Wal logging a full page image after a checkpoint wouldn't actually be
> enough since subsequent hint bits will dirty the page and not wal log
> anything creating a new torn page risk. FPI are only useful if all the
> subsequent updates are wal logged.
No, there's no new torn page risk, because any crash recovery would
replay starting from the checkpoint. You might lose the
subsequently-set hint bits, but that's okay.
regards, tom lane