Revert back-branch changes in behavior of age(xid).

tglsfdc · tglsfdc · commit 3dfaea4727fb · 2012-05-31T11:12:26.000-04:00
Per discussion, it does not seem like a good idea to change the behavior of age(xid) in a minor release, even though the old definition causes the function to fail on hot standby slaves. Therefore, revert commit 5829387 and follow-on commits in the back branches only.
diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
@@ -392,30 +392,6 @@ GetCurrentTransactionIdIfAny(void)
 	return CurrentTransactionState->transactionId;
 }
 
-/*
- *	GetStableLatestTransactionId
- *
- * Get the XID once and then return same value for rest of transaction.
- * Acts as a useful reference point for maintenance tasks.
- */
-TransactionId
-GetStableLatestTransactionId(void)
-{
-	static LocalTransactionId lxid = InvalidLocalTransactionId;
-	static TransactionId stablexid = InvalidTransactionId;
-
-	if (lxid != MyProc->lxid)
-	{
-		lxid = MyProc->lxid;
-		stablexid = GetTopTransactionIdIfAny();
-		if (!TransactionIdIsValid(stablexid))
-			stablexid = ReadNewTransactionId();
-	}
-
-	Assert(TransactionIdIsValid(stablexid));
-
-	return stablexid;
-}
 
 /*
  * AssignTransactionId
diff --git a/src/backend/utils/adt/xid.c b/src/backend/utils/adt/xid.c
@@ -87,13 +87,13 @@ xideq(PG_FUNCTION_ARGS)
 }
 
 /*
- *		xid_age			- compute age of an XID (relative to latest stable xid)
+ *		xid_age			- compute age of an XID (relative to current xact)
  */
 Datum
 xid_age(PG_FUNCTION_ARGS)
 {
 	TransactionId xid = PG_GETARG_TRANSACTIONID(0);
-	TransactionId now = GetStableLatestTransactionId();
+	TransactionId now = GetTopTransactionId();
 
 	/* Permanent XIDs are always infinitely old */
 	if (!TransactionIdIsNormal(xid))
diff --git a/src/include/access/xact.h b/src/include/access/xact.h
@@ -198,7 +198,6 @@ extern TransactionId GetTopTransactionId(void);
 extern TransactionId GetTopTransactionIdIfAny(void);
 extern TransactionId GetCurrentTransactionId(void);
 extern TransactionId GetCurrentTransactionIdIfAny(void);
-extern TransactionId GetStableLatestTransactionId(void);
 extern SubTransactionId GetCurrentSubTransactionId(void);
 extern CommandId GetCurrentCommandId(bool used);
 extern TimestampTz GetCurrentTransactionStartTimestamp(void);

Original file line number	Diff line number	Diff line change
`@@ -87,13 +87,13 @@ xideq(PG_FUNCTION_ARGS)`
`87`	`87`	`}`
`88`	`88`
`89`	`89`	`/*`
`90`		`- * xid_age - compute age of an XID (relative to latest stable xid)`
	`90`	`+ * xid_age - compute age of an XID (relative to current xact)`
`91`	`91`	`*/`
`92`	`92`	`Datum`
`93`	`93`	`xid_age(PG_FUNCTION_ARGS)`
`94`	`94`	`{`
`95`	`95`	`TransactionId xid = PG_GETARG_TRANSACTIONID(0);`
`96`		`- TransactionId now = GetStableLatestTransactionId();`
	`96`	`+ TransactionId now = GetTopTransactionId();`
`97`	`97`
`98`	`98`	`/* Permanent XIDs are always infinitely old */`
`99`	`99`	`if (!TransactionIdIsNormal(xid))`