On Fri, 3 Dec 2021 at 01:27, Dilip Kumar <dilipbal...@gmail.com> wrote:
> > On review, I think it is also possible that we update subtrans ONLY if > > someone uses >PGPROC_MAX_CACHED_SUBXIDS. > > This would make subtrans much smaller and avoid one-entry-per-page > > which is a major source of cacheing. > > This would means some light changes in GetSnapshotData(). > > Let me know if that seems interesting also? > > Do you mean to say avoid setting the sub-transactions parent if the > number of sun-transactions is not crossing PGPROC_MAX_CACHED_SUBXIDS? > But the TransactionIdDidCommit(), might need to fetch the parent if > the transaction status is TRANSACTION_STATUS_SUB_COMMITTED, so how > would we handle that? TRANSACTION_STATUS_SUB_COMMITTED is set as a transient state during final commit. In that case, the top-level xid is still in procarray when nsubxids < PGPROC_MAX_CACHED_SUBXIDS so we need not consult pg_subtrans in that case, see step 4 of TransactionIdIsInProgress() -- Simon Riggs http://www.EnterpriseDB.com/
