Refactor inCommit flag into generic delayChkpt flag.

Rename PGXACT->inCommit flag into delayChkpt flag,
and generalise comments to allow use in other situations,
such as the forthcoming potential use in checksum patch.
Replace wait loop to look for VXIDs with delayChkpt set.
No user visible changes, not behaviour changes at present.

Simon Riggs, reviewed and rebased by Jeff Davis

1 files changed, 18 insertions, 10 deletions

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 411807006ac..2b579f9b727 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -6884,8 +6884,8 @@ CreateCheckPoint(int flags)
 	XLogRecData rdata;
 	uint32		freespace;
 	XLogSegNo	_logSegNo;
-	TransactionId *inCommitXids;
-	int			nInCommit;
+	VirtualTransactionId *vxids;
+	int	nvxids;
 
 	/*
 	 * An end-of-recovery checkpoint is really a shutdown checkpoint, just
@@ -7056,9 +7056,14 @@ CreateCheckPoint(int flags)
 	TRACE_POSTGRESQL_CHECKPOINT_START(flags);
 
 	/*
-	 * Before flushing data, we must wait for any transactions that are
-	 * currently in their commit critical sections.  If an xact inserted its
-	 * commit record into XLOG just before the REDO point, then a crash
+	 * In some cases there are groups of actions that must all occur on
+	 * one side or the other of a checkpoint record. Before flushing the
+	 * checkpoint record we must explicitly wait for any backend currently
+	 * performing those groups of actions.
+	 *
+	 * One example is end of transaction, so we must wait for any transactions
+	 * that are currently in commit critical sections.  If an xact inserted
+	 * its commit record into XLOG just before the REDO point, then a crash
 	 * restart from the REDO point would not replay that record, which means
 	 * that our flushing had better include the xact's update of pg_clog.  So
 	 * we wait till he's out of his commit critical section before proceeding.
@@ -7073,21 +7078,24 @@ CreateCheckPoint(int flags)
 	 * protected by different locks, but again that seems best on grounds of
 	 * minimizing lock contention.)
 	 *
-	 * A transaction that has not yet set inCommit when we look cannot be at
+	 * A transaction that has not yet set delayChkpt when we look cannot be at
 	 * risk, since he's not inserted his commit record yet; and one that's
 	 * already cleared it is not at risk either, since he's done fixing clog
 	 * and we will correctly flush the update below.  So we cannot miss any
 	 * xacts we need to wait for.
 	 */
-	nInCommit = GetTransactionsInCommit(&inCommitXids);
-	if (nInCommit > 0)
+	vxids = GetVirtualXIDsDelayingChkpt(&nvxids);
+	if (nvxids > 0)
 	{
+		uint	nwaits = 0;
+
 		do
 		{
 			pg_usleep(10000L);	/* wait for 10 msec */
-		} while (HaveTransactionsInCommit(inCommitXids, nInCommit));
+			nwaits++;
+		} while (HaveVirtualXIDsDelayingChkpt(vxids, nvxids));
 	}
-	pfree(inCommitXids);
+	pfree(vxids);
 
 	/*
 	 * Get the other info we need for the checkpoint record.