Rewrite the FSM. Instead of relying on a fixed-size shared memory segment, the

free space information is stored in a dedicated FSM relation fork, with each
relation (except for hash indexes; they don't use FSM).

This eliminates the max_fsm_relations and max_fsm_pages GUC options; remove any
trace of them from the backend, initdb, and documentation.

Rewrite contrib/pg_freespacemap to match the new FSM implementation. Also
introduce a new variant of the get_raw_page(regclass, int4, int4) function in
contrib/pageinspect that let's you to return pages from any relation fork, and
a new fsm_page_contents() function to inspect the new FSM pages.

src/backend/access/gin/gininsert.c

@@ -8,7 +8,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *			$PostgreSQL: pgsql/src/backend/access/gin/gininsert.c,v 1.14 2008/07/11 21:06:29 tgl Exp $
+ *			$PostgreSQL: pgsql/src/backend/access/gin/gininsert.c,v 1.15 2008/09/30 10:52:10 heikki Exp $
  *-------------------------------------------------------------------------
  */
 
@@ -19,6 +19,7 @@
 #include "catalog/index.h"
 #include "miscadmin.h"
 #include "storage/bufmgr.h"
+#include "storage/indexfsm.h"
 #include "utils/memutils.h"
 
 
@@ -283,6 +284,9 @@ ginbuild(PG_FUNCTION_ARGS)
 		elog(ERROR, "index \"%s\" already contains data",
 			 RelationGetRelationName(index));
 
+	/* Initialize FSM */
+	InitIndexFreeSpaceMap(index);
+
 	initGinState(&buildstate.ginstate, index);
 
 	/* initialize the root page */