At Mon, 11 May 2020 20:12:04 -0400, Bruce Momjian <br...@momjian.us> wrote in > On Thu, May 7, 2020 at 09:22:02PM -0700, Noah Misch wrote: > > On Thu, May 07, 2020 at 09:38:34AM -0400, Bruce Momjian wrote: > > > > > > - Crash recovery was losing tuples written via COPY TO. This fixes > > > > > > the bug. > > > > > > > > > > This was not backpatched? > > > > > > > > Right. > > > > > > Oh. So you are saying we could lose COPY data on a crash, even after a > > > commit. That seems bad. Can you show me the commit info? I can't find > > > it. > > > > commit c6b9204 > > Author: Noah Misch <n...@leadboat.com> > > AuthorDate: Sat Apr 4 12:25:34 2020 -0700 > > Commit: Noah Misch <n...@leadboat.com> > > CommitDate: Sat Apr 4 12:25:34 2020 -0700 > > > > Skip WAL for new relfilenodes, under wal_level=minimal. > > > > Until now, only selected bulk operations (e.g. COPY) did this. If a > > given relfilenode received both a WAL-skipping COPY and a WAL-logged > > operation (e.g. INSERT), recovery could lose tuples from the COPY. See > > src/backend/access/transam/README section "Skipping WAL for New > > RelFileNode" for the new coding rules. Maintainers of table access > > methods should examine that section. > > OK, so how do we want to document this? Do I mention in the text below > the WAL skipping item that this fixes a bug where a mix of simultaneous > COPY and INSERT into a table could lose rows during crash recovery, or > create a new item?
FWIW, as dicussed upthread, I suppose that the API change is not going to be in relnotes. something like this? - Fix bug of WAL-skipping optimiazation Previously a trasaction doing both of COPY and a WAL-logged operations like INSERT while wal_level=minimal can lead to loss of COPY'ed rows through crash recovery. Also this fix extends the WAL-skipping optimiazation to all kinds of bulk insert operations. regards. -- Kyotaro Horiguchi NTT Open Source Software Center
