From b06679e01244d33304b71a6a44c7cc86173617b3 Mon Sep 17 00:00:00 2001
From: Simon Riggs <simon@2ndQuadrant.com>
Date: Fri, 11 May 2012 14:36:24 +0100
Subject: Ensure age() returns a stable value rather than the latest value

---
 src/backend/utils/adt/xid.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

(limited to 'src/backend/utils/adt/xid.c')

diff --git a/src/backend/utils/adt/xid.c b/src/backend/utils/adt/xid.c
index eeda081ad18..da9da8a29b9 100644
--- a/src/backend/utils/adt/xid.c
+++ b/src/backend/utils/adt/xid.c
@@ -19,6 +19,7 @@
 #include "access/transam.h"
 #include "access/xact.h"
 #include "libpq/pqformat.h"
+#include "storage/proc.h"
 #include "utils/builtins.h"
 
 #define PG_GETARG_TRANSACTIONID(n)	DatumGetTransactionId(PG_GETARG_DATUM(n))
@@ -87,16 +88,13 @@ xideq(PG_FUNCTION_ARGS)
 }
 
 /*
- *		xid_age			- compute age of an XID (relative to current xact)
+ *		xid_age			- compute age of an XID (relative to latest stable xid)
  */
 Datum
 xid_age(PG_FUNCTION_ARGS)
 {
 	TransactionId xid = PG_GETARG_TRANSACTIONID(0);
-	TransactionId now = GetTopTransactionIdIfAny();
-
-	if (!TransactionIdIsValid(now))
-		now = ReadNewTransactionId();
+	TransactionId now = GetStableLatestTransactionId();
 
 	/* Permanent XIDs are always infinitely old */
 	if (!TransactionIdIsNormal(xid))
-- 
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