Re: Deriving Recovery Snapshots

Simon Riggs wrote:
> The patch isn't ready to apply standalone because we need to include the
> changes to XidInMVCCSnapshot() also, which would take a little while to
> extract. Let me know if that is worth producing a standalone patch for.

FWIW, this patch becomes a lot simpler if you don't change the function
signature, and don't move the SubtransSetParent() call.

--
   Heikki Linnakangas
   EnterpriseDB   http://www.enterprisedb.com
*** src/backend/access/transam/xact.c
--- src/backend/access/transam/xact.c
***************
*** 404,419 **** AssignTransactionId(TransactionState s)
          AssignTransactionId(s->parent);

      /*
!      * Generate a new Xid and record it in PG_PROC and pg_subtrans.
!      *
!      * NB: we must make the subtrans entry BEFORE the Xid appears anywhere in
!      * shared storage other than PG_PROC; because if there's no room for it in
!      * PG_PROC, the subtrans entry is needed to ensure that other backends see
!      * the Xid as "running".  See GetNewTransactionId.
       */
      s->transactionId = GetNewTransactionId(isSubXact);

!     if (isSubXact)
          SubTransSetParent(s->transactionId, s->parent->transactionId);

      /*
--- 404,418 ----
          AssignTransactionId(s->parent);

      /*
!      * Generate a new Xid and record it in PG_PROC. If there's no room
!      * in MyProc-> in MyProc->subxids, we must make the pg_subtrans
!      * entry BEFORE the Xid appears anywhere in shared storage other than
!      * PG_PROC, because the subtrans entry is needed to ensure that other
!      * backends see the Xid as "running".
       */
      s->transactionId = GetNewTransactionId(isSubXact);

!     if (isSubXact && MyProc->subxids.overflowed)
          SubTransSetParent(s->transactionId, s->parent->transactionId);

      /*