Fix recently-understood problems with handling of XID freezing, particularly

in PITR scenarios.  We now WAL-log the replacement of old XIDs with
FrozenTransactionId, so that such replacement is guaranteed to propagate to
PITR slave databases.  Also, rather than relying on hint-bit updates to be
preserved, pg_clog is not truncated until all instances of an XID are known to
have been replaced by FrozenTransactionId.  Add new GUC variables and
pg_autovacuum columns to allow management of the freezing policy, so that
users can trade off the size of pg_clog against the amount of freezing work
done.  Revise the already-existing code that forces autovacuum of tables
approaching the wraparound point to make it more bulletproof; also, revise the
autovacuum logic so that anti-wraparound vacuuming is done per-table rather
than per-database.  initdb forced because of changes in pg_class, pg_database,
and pg_autovacuum catalogs.  Heikki Linnakangas, Simon Riggs, and Tom Lane.

src/include/access/xlog.h

@@ -6,7 +6,7 @@
  * Portions Copyright (c) 1996-2006, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/access/xlog.h,v 1.74 2006/08/21 16:16:31 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/access/xlog.h,v 1.75 2006/11/05 22:42:10 tgl Exp $
  */
 #ifndef XLOG_H
 #define XLOG_H
@@ -165,7 +165,6 @@ extern void InitXLOGAccess(void);
 extern void CreateCheckPoint(bool shutdown, bool force);
 extern void XLogPutNextOid(Oid nextOid);
 extern XLogRecPtr GetRedoRecPtr(void);
-extern TransactionId GetRecentNextXid(void);
 extern void GetNextXidAndEpoch(TransactionId *xid, uint32 *epoch);
 
 #endif   /* XLOG_H */