Kyotaro Horiguchi <horikyota....@gmail.com> wrote: > At Mon, 11 Nov 2019 10:03:14 +0100, Antonin Houska <a...@cybertec.at> wrote > in > > Michael Paquier <mich...@paquier.xyz> wrote: > > > Does something like the attached patch make sense? Reviews are > > > welcome. > > > > This looks good to me. > > I have a qustion. > > The current code assumes that !BM_DIRTY means that the function is > dirtying the page. But if !BM_JUST_DIRTIED, the function actually is > going to re-dirty the page even if BM_DIRTY.
It makes sense to me. I can imagine the following: 1. FlushBuffer() cleared BM_JUST_DIRTIED, wrote the page to disk but hasn't yet cleared BM_DIRTY. 2. Another backend changed a hint bit in shared memory and called MarkBufferDirtyHint(). Thus FlushBuffer() missed the current hint bit change, so we need to dirty the page again. > If this is correct, the trigger for stats update is not !BM_DIRTY but > !BM_JUST_DIRTIED, or the fact that we passed the line of > XLogSaveBufferForHint() could be the trigger, regardless whether the > LSN is valid or not. I agree. -- Antonin Houska Web: https://www.cybertec-postgresql.com
