From: Pavan Deolasee <pavan.deolasee@gmail.com>
Date: Thu, 21 Jan 2016 13:58:27 +0000 (+0530)
Subject: Assign coordinator local timestamp when transaction timestamp is requested
X-Git-Tag: XL9_5_R1BETA1~83
X-Git-Url: http://git.postgresql.org/gitweb/static/gitweb.js?a=commitdiff_plain;h=0cb4cbc7db1179000378d54e9bcb12abb19d2ee5;p=postgres-xl.git

Assign coordinator local timestamp when transaction timestamp is requested
before or without assigning XID to the transaction.

GTM supplied timestamp is available only when a transaction has started on the
GTM. But for read-only transactions or transactions which are yet to do any
database write activity, we avoid going to GTM for performance reason. For such
cases, use coordinator local timestamp and continue to use the same for rest of
the transaction.
---

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index e615c7e2c9..f42d8d3d1c 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -685,7 +685,8 @@ AssignTransactionId(TransactionState s)
 		s->transactionId = GetNewTransactionId(isSubXact, &received_tp, &gtm_timestamp);
 		if (received_tp)
 		{
-			GTMxactStartTimestamp = (TimestampTz) gtm_timestamp;
+			if (GTMxactStartTimestamp == 0)
+				GTMxactStartTimestamp = (TimestampTz) gtm_timestamp;
 			GTMdeltaTimestamp = GTMxactStartTimestamp - stmtStartTimestamp;
 		}
 	}
@@ -905,6 +906,8 @@ GetCurrentTransactionStartTimestamp(void)
 	 * from GTM along with GXID.
 	 */
 #ifdef PGXC
+	if (GTMxactStartTimestamp == 0)
+		GTMxactStartTimestamp = xactStartTimestamp;
 	return GTMxactStartTimestamp;
 #else
 	return xactStartTimestamp;
@@ -964,6 +967,8 @@ GetCurrentTransactionStopTimestamp(void)
 TimestampTz
 GetCurrentGTMStartTimestamp(void)
 {
+	if (GTMxactStartTimestamp == 0)
+		GTMxactStartTimestamp = xactStartTimestamp;
 	return GTMxactStartTimestamp;
 }
 #endif
@@ -995,7 +1000,8 @@ SetCurrentTransactionStopTimestamp(void)
 void
 SetCurrentGTMDeltaTimestamp(TimestampTz timestamp)
 {
-	GTMxactStartTimestamp = timestamp;
+	if (GTMxactStartTimestamp == 0)
+		GTMxactStartTimestamp = timestamp;
 	GTMdeltaTimestamp = GTMxactStartTimestamp - xactStartTimestamp;
 }
 #endif
@@ -2193,7 +2199,9 @@ StartTransaction(void)
 	xactStopTimestamp = 0;
 #ifdef PGXC
 	/* For Postgres-XC, transaction start timestamp has to follow the GTM timeline */
-	pgstat_report_xact_timestamp(GTMxactStartTimestamp);
+	pgstat_report_xact_timestamp(GTMxactStartTimestamp ?
+			GTMxactStartTimestamp :
+			xactStartTimestamp);
 #else
 	pgstat_report_xact_timestamp(xactStartTimestamp);
 #endif
@@ -2650,6 +2658,7 @@ CommitTransaction(void)
 
 #ifdef PGXC
 	AtEOXact_Remote();
+	GTMxactStartTimestamp = 0;
 #endif
 }
 
@@ -3026,6 +3035,7 @@ PrepareTransaction(void)
 	CleanGTMCallbacks();
 #ifdef XCP	
 	AtEOXact_Remote();	
+	GTMxactStartTimestamp = 0;
 #endif	
 #endif
 
@@ -3318,6 +3328,7 @@ AbortTransaction(void)
 
 #ifdef PGXC
 	AtEOXact_Remote();
+	GTMxactStartTimestamp = 0;
 #endif
 
 }