On Mon, Nov 04, 2019 at 03:26:35PM +1300, Thomas Munro wrote: > On Thu, Aug 1, 2019 at 6:51 PM Noah Misch <n...@leadboat.com> wrote: > > vac_truncate_clog() instance 1 starts, considers segment ABCD eligible to > > unlink > > vac_truncate_clog() instance 2 starts, considers segment ABCD eligible to > > unlink > > vac_truncate_clog() instance 1 unlinks segment ABCD > > vac_truncate_clog() instance 1 calls SetTransactionIdLimit() > > vac_truncate_clog() instance 1 finishes > > some backend calls SimpleLruZeroPage(), creating segment ABCD > > vac_truncate_clog() instance 2 unlinks segment ABCD > > > > Serializing vac_truncate_clog() fixes that. > > I've wondered before (in a -bugs thread[1] about unexplained pg_serial > wraparound warnings) if we could map 64 bit xids to wide SLRU file > names that never wrap around and make this class of problem go away. > Unfortunately multixacts would need 64 bit support too... > > [1] > https://www.postgresql.org/message-id/flat/CAEBTBzuS-01t12GGVD6qCezce8EFD8aZ1V%2Bo_3BZ%3DbuVLQBtRg%40mail.gmail.com
That change sounds good to me.
