On Sun, Mar 29, 2020 at 6:29 AM Tomas Vondra <tomas.von...@2ndquadrant.com> wrote: > > On Sat, Mar 28, 2020 at 03:29:34PM +0530, Amit Kapila wrote: > >On Sat, Mar 28, 2020 at 2:19 PM Dilip Kumar <dilipbal...@gmail.com> wrote: > > > >How about if instead of writing an XLOG_XACT_ASSIGNMENT WAL, we set a > >flag in TransactionStateData and then log that as special information > >whenever we write next WAL record for a new subtransaction? Then > >during recovery, we can only call ProcArrayApplyXidAssignment when we > >find that special flag is set in a WAL record. One idea could be to > >use a flag bit in XLogRecord.xl_info. If that is feasible then the > >solution can work as it is now, without any overhead or change in the > >way we maintain KnownAssignedXids. > > > > Ummm, how is that different from what the patch is doing now? I mean, we > only write the top-level XID for the first WAL record in each subxact, > right? Or what would be the difference with your approach? >
We have to do what the patch is currently doing and additionally, we will set this flag after PGPROC_MAX_CACHED_SUBXIDS which would allow us to call ProcArrayApplyXidAssignment during WAL replay only after PGPROC_MAX_CACHED_SUBXIDS number of subxacts. It will help us in clearing the KnownAssignedXids at the same time as we do now, so no additional performance overhead. -- With Regards, Amit Kapila. EnterpriseDB: http://www.enterprisedb.com
