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have been replaced by FrozenTransactionId.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/rmgr.h

@@ -3,7 +3,7 @@
  *
  * Resource managers definition
  *
- * $PostgreSQL: pgsql/src/include/access/rmgr.h,v 1.16 2006/05/02 11:28:55 teodor Exp $
+ * $PostgreSQL: pgsql/src/include/access/rmgr.h,v 1.17 2006/11/05 22:42:10 tgl Exp $
  */
 #ifndef RMGR_H
 #define RMGR_H
@@ -12,6 +12,9 @@ typedef uint8 RmgrId;
 
 /*
  * Built-in resource managers
+ *
+ * Note: RM_MAX_ID could be as much as 255 without breaking the XLOG file
+ * format, but we keep it small to minimize the size of RmgrTable[].
  */
 #define RM_XLOG_ID				0
 #define RM_XACT_ID				1
@@ -20,6 +23,7 @@ typedef uint8 RmgrId;
 #define RM_DBASE_ID				4
 #define RM_TBLSPC_ID			5
 #define RM_MULTIXACT_ID			6
+#define RM_HEAP2_ID				9
 #define RM_HEAP_ID				10
 #define RM_BTREE_ID				11
 #define RM_HASH_ID				12