Ensure backwards compatibility for GetStableLatestTransactionId()

simonat2ndQuadrant · simonat2ndQuadrant · commit 867540b49cd2 · 2012-05-12T13:26:10.000+01:00
diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
@@ -390,11 +390,10 @@ 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
@@ -403,13 +402,16 @@ 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
`@@ -390,11 +390,10 @@ GetCurrentTransactionIdIfAny(void)`
`390`	`390`	`return CurrentTransactionState->transactionId;`
`391`	`391`	`}`
`392`	`392`
`393`		`-`
`394`	`393`	`/*`
`395`		`- * GetStableLatestTransactionIdIfAny`
	`394`	`+ * GetStableLatestTransactionId`
`396`	`395`	`*`
`397`		`- * Get the latest XID once and then return same value for rest of transaction.`
	`396`	`+ * Get the XID once and then return same value for rest of transaction.`
`398`	`397`	`* Acts as a useful reference point for maintenance tasks.`
`399`	`398`	`*/`
`400`	`399`	`TransactionId`
`@@ -403,13 +402,16 @@ GetStableLatestTransactionId(void)`
`403`	`402`	`static LocalTransactionId lxid = InvalidLocalTransactionId;`
`404`	`403`	`static TransactionId stablexid = InvalidTransactionId;`
`405`	`404`
`406`		`- if (lxid != MyProc->lxid \|\|`
`407`		`- !TransactionIdIsValid(stablexid))`
	`405`	`+ if (lxid != MyProc->lxid)`
`408`	`406`	`{`
`409`	`407`	`lxid = MyProc->lxid;`
`410`		`- stablexid = ReadNewTransactionId();`
	`408`	`+ stablexid = GetTopTransactionIdIfAny();`
	`409`	`+ if (!TransactionIdIsValid(stablexid))`
	`410`	`+ stablexid = ReadNewTransactionId();`
`411`	`411`	`}`
`412`	`412`
	`413`	`+ Assert(TransactionIdIsValid(stablexid));`
	`414`	`+`
`413`	`415`	`return stablexid;`
`414`	`416`	`}`
`415`	`417`