Ensure backwards compatibility for GetStableLatestTransactionId()

simonat2ndQuadrant · simonat2ndQuadrant · commit 436af241c88a · 2012-05-12T13:25:34.000+01:00
diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
@@ -392,11 +392,10 @@ GetCurrentTransactionIdIfAny(void)
 	return CurrentTransactionState->transactionId;
 }
 
-
 /*
- *	GetStableLatestTransactionIdIfAny
+ *	GetStableLatestTransactionId
  *
- * Get the latest XID once and then return same value for rest of transaction.
+ * Get the XID once and then return same value for rest of transaction.
  * Acts as a useful reference point for maintenance tasks.
  */
 TransactionId
@@ -405,13 +404,16 @@ GetStableLatestTransactionId(void)
 	static LocalTransactionId lxid = InvalidLocalTransactionId;
 	static TransactionId stablexid = InvalidTransactionId;
 
-	if (lxid != MyProc->lxid ||
-		!TransactionIdIsValid(stablexid))
+	if (lxid != MyProc->lxid)
 	{
 		lxid = MyProc->lxid;
-		stablexid = ReadNewTransactionId();
+		stablexid = GetTopTransactionIdIfAny();
+		if (!TransactionIdIsValid(stablexid))
+			stablexid = ReadNewTransactionId();
 	}
 
+	Assert(TransactionIdIsValid(stablexid));
+
 	return stablexid;
 }
 

Original file line number	Diff line number	Diff line change
`@@ -392,11 +392,10 @@ GetCurrentTransactionIdIfAny(void)`
`392`	`392`	`return CurrentTransactionState->transactionId;`
`393`	`393`	`}`
`394`	`394`
`395`		`-`
`396`	`395`	`/*`
`397`		`- * GetStableLatestTransactionIdIfAny`
	`396`	`+ * GetStableLatestTransactionId`
`398`	`397`	`*`
`399`		`- * Get the latest XID once and then return same value for rest of transaction.`
	`398`	`+ * Get the XID once and then return same value for rest of transaction.`
`400`	`399`	`* Acts as a useful reference point for maintenance tasks.`
`401`	`400`	`*/`
`402`	`401`	`TransactionId`
`@@ -405,13 +404,16 @@ GetStableLatestTransactionId(void)`
`405`	`404`	`static LocalTransactionId lxid = InvalidLocalTransactionId;`
`406`	`405`	`static TransactionId stablexid = InvalidTransactionId;`
`407`	`406`
`408`		`- if (lxid != MyProc->lxid \|\|`
`409`		`- !TransactionIdIsValid(stablexid))`
	`407`	`+ if (lxid != MyProc->lxid)`
`410`	`408`	`{`
`411`	`409`	`lxid = MyProc->lxid;`
`412`		`- stablexid = ReadNewTransactionId();`
	`410`	`+ stablexid = GetTopTransactionIdIfAny();`
	`411`	`+ if (!TransactionIdIsValid(stablexid))`
	`412`	`+ stablexid = ReadNewTransactionId();`
`413`	`413`	`}`
`414`	`414`
	`415`	`+ Assert(TransactionIdIsValid(stablexid));`
	`416`	`+`
`415`	`417`	`return stablexid;`
`416`	`418`	`}`
`417`	`419`