*** pgsql/src/backend/utils/adt/xid.c	2009/01/01 17:23:50	1.12
--- pgsql/src/backend/utils/adt/xid.c	2009/12/19 01:32:36	1.13
***************
*** 8,14 ****
   *
   *
   * IDENTIFICATION
!  *	  $PostgreSQL: pgsql/src/backend/utils/adt/xid.c,v 1.11 2008/01/01 19:45:53 momjian Exp $
   *
   *-------------------------------------------------------------------------
   */
--- 8,14 ----
   *
   *
   * IDENTIFICATION
!  *	  $PostgreSQL: pgsql/src/backend/utils/adt/xid.c,v 1.12 2009/01/01 17:23:50 momjian Exp $
   *
   *-------------------------------------------------------------------------
   */
*************** xid_age(PG_FUNCTION_ARGS)
*** 102,107 ****
--- 102,126 ----
  	PG_RETURN_INT32((int32) (now - xid));
  }
  
+ /*
+  * xidComparator
+  *		qsort comparison function for XIDs
+  *
+  * We can't use wraparound comparison for XIDs because that does not respect
+  * the triangle inequality!  Any old sort order will do.
+  */
+ int
+ xidComparator(const void *arg1, const void *arg2)
+ {
+ 	TransactionId xid1 = *(const TransactionId *) arg1;
+ 	TransactionId xid2 = *(const TransactionId *) arg2;
+ 
+ 	if (xid1 > xid2)
+ 		return 1;
+ 	if (xid1 < xid2)
+ 		return -1;
+ 	return 0;
+ }
  
  /*****************************************************************************
   *	 COMMAND IDENTIFIER ROUTINES											 *