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.

contrib/pageinspect/Makefile

@@ -2,12 +2,12 @@
 #
 # pageinspect Makefile
 #
-# $PostgreSQL: pgsql/contrib/pageinspect/Makefile,v 1.3 2007/11/10 23:59:51 momjian Exp $
+# $PostgreSQL: pgsql/contrib/pageinspect/Makefile,v 1.4 2008/09/30 10:52:09 heikki Exp $
 #
 #-------------------------------------------------------------------------
 
 MODULE_big	= pageinspect
-OBJS		= rawpage.o heapfuncs.o btreefuncs.o
+OBJS		= rawpage.o heapfuncs.o btreefuncs.o fsmfuncs.o
 DATA_built	= pageinspect.sql
 DATA      	= uninstall_pageinspect.sql
 

contrib/pageinspect/fsmfuncs.c

@@ -0,0 +1,61 @@
+/*-------------------------------------------------------------------------
+ *
+ * fsmfuncs.c
+ *	  Functions to investigate FSM pages
+ *
+ * These functions are restricted to superusers for the fear of introducing
+ * security holes if the input checking isn't as water-tight as it should.
+ * You'd need to be superuser to obtain a raw page image anyway, so
+ * there's hardly any use case for using these without superuser-rights
+ * anyway.
+ *
+ * Copyright (c) 2007-2008, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  $PostgreSQL: pgsql/contrib/pageinspect/fsmfuncs.c,v 1.1 2008/09/30 10:52:09 heikki Exp $
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+#include "lib/stringinfo.h"
+#include "storage/fsm_internals.h"
+#include "utils/builtins.h"
+#include "miscadmin.h"
+#include "funcapi.h"
+
+Datum fsm_page_contents(PG_FUNCTION_ARGS);
+
+/*
+ * Dumps the contents of a FSM page.
+ */
+PG_FUNCTION_INFO_V1(fsm_page_contents);
+
+Datum
+fsm_page_contents(PG_FUNCTION_ARGS)
+{
+	bytea	   *raw_page = PG_GETARG_BYTEA_P(0);
+	int			raw_page_size;
+	StringInfoData sinfo;
+	FSMPage		fsmpage;
+	int			i;
+
+	if (!superuser())
+		ereport(ERROR,
+				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
+				 (errmsg("must be superuser to use raw page functions"))));
+
+	raw_page_size = VARSIZE(raw_page) - VARHDRSZ;
+	fsmpage = (FSMPage) PageGetContents(VARDATA(raw_page));
+
+	initStringInfo(&sinfo);
+
+	for(i=0; i < NodesPerPage; i++)
+	{
+		if (fsmpage->fp_nodes[i] != 0)
+			appendStringInfo(&sinfo, "%d: %d\n", i, fsmpage->fp_nodes[i]);
+	}
+	appendStringInfo(&sinfo, "fp_next_slot: %d\n", fsmpage->fp_next_slot);
+
+	PG_RETURN_TEXT_P(cstring_to_text(sinfo.data));
+}

contrib/pageinspect/pageinspect.sql.in

@@ -1,4 +1,4 @@
-/* $PostgreSQL: pgsql/contrib/pageinspect/pageinspect.sql.in,v 1.4 2007/11/13 04:24:28 momjian Exp $ */
+/* $PostgreSQL: pgsql/contrib/pageinspect/pageinspect.sql.in,v 1.5 2008/09/30 10:52:09 heikki Exp $ */
 
 -- Adjust this setting to control where the objects get created.
 SET search_path = public;
@@ -6,11 +6,16 @@ SET search_path = public;
 --
 -- get_raw_page()
 --
-CREATE OR REPLACE FUNCTION get_raw_page(text, int4)
+CREATE OR REPLACE FUNCTION get_raw_page(text, int4, int4)
 RETURNS bytea
 AS 'MODULE_PATHNAME', 'get_raw_page'
 LANGUAGE C STRICT;
 
+CREATE OR REPLACE FUNCTION get_raw_page(text, int4) 
+RETURNS bytea
+AS $$ SELECT get_raw_page($1, 0, $2); $$
+LANGUAGE SQL STRICT;
+
 --
 -- page_header()
 --
@@ -92,3 +97,11 @@ CREATE OR REPLACE FUNCTION bt_page_items(IN relname text, IN blkno int4,
 RETURNS SETOF record
 AS 'MODULE_PATHNAME', 'bt_page_items'
 LANGUAGE C STRICT;
+
+--
+-- fsm_page_contents()
+--
+CREATE OR REPLACE FUNCTION fsm_page_contents(IN page bytea)
+RETURNS text
+AS 'MODULE_PATHNAME', 'fsm_page_contents'
+LANGUAGE C STRICT;

contrib/pageinspect/rawpage.c

@@ -8,7 +8,7 @@
  * Copyright (c) 2007-2008, PostgreSQL Global Development Group
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/contrib/pageinspect/rawpage.c,v 1.6 2008/05/12 00:00:43 alvherre Exp $
+ *	  $PostgreSQL: pgsql/contrib/pageinspect/rawpage.c,v 1.7 2008/09/30 10:52:09 heikki Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -41,7 +41,8 @@ Datum
 get_raw_page(PG_FUNCTION_ARGS)
 {
 	text	   *relname = PG_GETARG_TEXT_P(0);
-	uint32		blkno = PG_GETARG_UINT32(1);
+	uint32		forknum = PG_GETARG_UINT32(1);
+	uint32		blkno = PG_GETARG_UINT32(2);
 
 	Relation	rel;
 	RangeVar   *relrv;
@@ -54,6 +55,11 @@ get_raw_page(PG_FUNCTION_ARGS)
 				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
 				 (errmsg("must be superuser to use raw functions"))));
 
+	if (forknum > MAX_FORKNUM)
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+				 errmsg("invalid fork number")));
+
 	relrv = makeRangeVarFromNameList(textToQualifiedNameList(relname));
 	rel = relation_openrv(relrv, AccessShareLock);
 
@@ -80,7 +86,7 @@ get_raw_page(PG_FUNCTION_ARGS)
 
 	/* Take a verbatim copy of the page */
 
-	buf = ReadBuffer(rel, blkno);
+	buf = ReadBufferWithFork(rel, forknum, blkno);
 	LockBuffer(buf, BUFFER_LOCK_SHARE);
 
 	memcpy(raw_page_data, BufferGetPage(buf), BLCKSZ);

contrib/pg_freespacemap/pg_freespacemap.sql.in

@@ -1,44 +1,26 @@
-/* $PostgreSQL: pgsql/contrib/pg_freespacemap/pg_freespacemap.sql.in,v 1.8 2007/11/13 04:24:28 momjian Exp $ */
+/* $PostgreSQL: pgsql/contrib/pg_freespacemap/pg_freespacemap.sql.in,v 1.9 2008/09/30 10:52:09 heikki Exp $ */
 
 -- Adjust this setting to control where the objects get created.
 SET search_path = public;
 
 
--- Register the functions.
-CREATE OR REPLACE FUNCTION pg_freespacemap_pages()
-RETURNS SETOF RECORD
-AS 'MODULE_PATHNAME', 'pg_freespacemap_pages'
+-- Register the C function.
+CREATE OR REPLACE FUNCTION pg_freespace(regclass, int4)
+RETURNS int2
+AS 'MODULE_PATHNAME', 'pg_freespace'
 LANGUAGE C;
 
-CREATE OR REPLACE FUNCTION pg_freespacemap_relations()
+-- pg_freespace shows the recorded space avail at each block in a relation
+CREATE OR REPLACE FUNCTION
+  pg_freespace(rel regclass, blkno OUT int4, avail OUT int2)
 RETURNS SETOF RECORD
-AS 'MODULE_PATHNAME', 'pg_freespacemap_relations'
-LANGUAGE C;
+AS $$
+  SELECT blkno::int4, pg_freespace($1, blkno::int4) AS avail
+  FROM generate_series(0, pg_relation_size($1) / current_setting('block_size')::bigint - 1) AS blkno;
+$$
+LANGUAGE SQL;
 
 
--- Create views for convenient access.
-CREATE VIEW pg_freespacemap_pages AS
-	SELECT P.* FROM pg_freespacemap_pages() AS P
-	(reltablespace oid,
-	 reldatabase oid,
-	 relfilenode oid,
-	 relblocknumber bigint,
-	 bytes integer);
- 
-CREATE VIEW pg_freespacemap_relations AS
-	SELECT P.* FROM pg_freespacemap_relations() AS P
-	(reltablespace oid,
-	 reldatabase oid,
-	 relfilenode oid,
-	 avgrequest integer,
-	 interestingpages integer,
-	 storedpages integer,
-	 nextpage integer);
-
- 
 -- Don't want these to be available to public.
-REVOKE ALL ON FUNCTION pg_freespacemap_pages() FROM PUBLIC;
-REVOKE ALL ON pg_freespacemap_pages FROM PUBLIC;
-
-REVOKE ALL ON FUNCTION pg_freespacemap_relations() FROM PUBLIC;
-REVOKE ALL ON pg_freespacemap_relations FROM PUBLIC;
+REVOKE ALL ON FUNCTION pg_freespace(regclass, int4) FROM PUBLIC;
+REVOKE ALL ON FUNCTION pg_freespace(regclass) FROM PUBLIC;