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
