Extend commit, subtrans and commit_ts logs appropriately when new xids are

received from the GTM.

After our recent work on cluster monitor, GTM will now send back
latestCompletedXid and RecentGlobalXmin which we record in a shared memory
area. But if the node has not asked for XIDs for some time, the SLRU
maintaining these logs may fall much behind. So we must keep these log files
upto date with the XIDs generated by the GTM

This should also fix the spotting of the following log message as reported
by Mason Sharp

LOG: could not truncate directory "pg_subtrans": apparent wraparound

4 files changed, 28 insertions, 0 deletions

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 1e601a68ca..56844d7001 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -777,3 +777,15 @@ GetNewObjectId(void)
 
 	return result;
 }
+
+#ifdef XCP
+void
+ExtendLogs(TransactionId xid)
+{
+	LWLockAcquire(XidGenLock, LW_EXCLUSIVE);
+	ExtendCLOG(xid);
+	ExtendCommitTs(xid);
+	ExtendSUBTRANS(xid);
+	LWLockRelease(XidGenLock);
+}
+#endif
diff --git a/src/backend/postmaster/clustermon.c b/src/backend/postmaster/clustermon.c
index 2ff09787ed..e2dda4f7f3 100644
--- a/src/backend/postmaster/clustermon.c
+++ b/src/backend/postmaster/clustermon.c
@@ -378,6 +378,14 @@ ClusterMonitorGetGlobalXmin(void)
 void
 ClusterMonitorSetGlobalXmin(GlobalTransactionId xmin)
 {
+	/*
+	 * First extend the commit logs. Even though we may not have actually
+	 * started any transactions in the new range, we must still extend the logs
+	 * so that later operations which rely on the RecentGlobalXmin to truncate
+	 * the logs work correctly.
+	 */
+	ExtendLogs(xmin);
+
 	LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
 
 	/*
diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c
index 216891485b..84b6a87d0d 100644
--- a/src/backend/storage/ipc/procarray.c
+++ b/src/backend/storage/ipc/procarray.c
@@ -4408,6 +4408,13 @@ SetLatestCompletedXid(TransactionId latestCompletedXid)
 
 	if (!TransactionIdIsValid(latestCompletedXid))
 		return;
+	/*
+	 * First extend the commit logs. Even though we may not have actually
+	 * started any transactions in the new range, we must still extend the logs
+	 * so that later operations which may try to query them based on the new
+	 * value of latestCompletedXid do not throw errors
+	 */
+	ExtendLogs(latestCompletedXid);
 
 	LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
 
diff --git a/src/include/access/transam.h b/src/include/access/transam.h
index 3011493cfa..c5ce762fba 100644
--- a/src/include/access/transam.h
+++ b/src/include/access/transam.h
@@ -188,6 +188,7 @@ extern TransactionId GetNewTransactionId(bool isSubXact);
 #ifdef XCP
 extern bool TransactionIdIsCurrentGlobalTransactionId(TransactionId xid);
 extern TransactionId GetNextTransactionId(void);
+extern void ExtendLogs(TransactionId xid);
 #endif
 extern TransactionId ReadNewTransactionId(void);
 extern void SetTransactionIdLimit(TransactionId oldest_datfrozenxid,