Ensure backwards compatibility for GetStableLatestTransactionId()

simonat2ndQuadrant · simonat2ndQuadrant · commit 37edecfdfe21 · 2012-05-12T13:24:15.000+01:00
diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
@@ -386,11 +386,10 @@ 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
@@ -399,13 +398,16 @@ 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
`@@ -386,11 +386,10 @@ GetCurrentTransactionIdIfAny(void)`
`386`	`386`	`return CurrentTransactionState->transactionId;`
`387`	`387`	`}`
`388`	`388`
`389`		`-`
`390`	`389`	`/*`
`391`		`- * GetStableLatestTransactionIdIfAny`
	`390`	`+ * GetStableLatestTransactionId`
`392`	`391`	`*`
`393`		`- * Get the latest XID once and then return same value for rest of transaction.`
	`392`	`+ * Get the XID once and then return same value for rest of transaction.`
`394`	`393`	`* Acts as a useful reference point for maintenance tasks.`
`395`	`394`	`*/`
`396`	`395`	`TransactionId`
`@@ -399,13 +398,16 @@ GetStableLatestTransactionId(void)`
`399`	`398`	`static LocalTransactionId lxid = InvalidLocalTransactionId;`
`400`	`399`	`static TransactionId stablexid = InvalidTransactionId;`
`401`	`400`
`402`		`- if (lxid != MyProc->lxid \|\|`
`403`		`- !TransactionIdIsValid(stablexid))`
	`401`	`+ if (lxid != MyProc->lxid)`
`404`	`402`	`{`
`405`	`403`	`lxid = MyProc->lxid;`
`406`		`- stablexid = ReadNewTransactionId();`
	`404`	`+ stablexid = GetTopTransactionIdIfAny();`
	`405`	`+ if (!TransactionIdIsValid(stablexid))`
	`406`	`+ stablexid = ReadNewTransactionId();`
`407`	`407`	`}`
`408`	`408`
	`409`	`+ Assert(TransactionIdIsValid(stablexid));`
	`410`	`+`
`409`	`411`	`return stablexid;`
`410`	`412`	`}`
`411`	`413`