Install infrastructure for shared-memory free space map. Doesn't actually

do anything yet, but it has the necessary connections to initialization
and so forth.  Make some gestures towards allowing number of blocks in
a relation to be BlockNumber, ie, unsigned int, rather than signed int.
(I doubt I got all the places that are sloppy about it, yet.)  On the
way, replace the hardwired NLOCKS_PER_XACT fudge factor with a GUC
variable.

src/include/storage/freespace.h

@@ -0,0 +1,53 @@
+/*-------------------------------------------------------------------------
+ *
+ * freespace.h
+ *	  POSTGRES free space map for quickly finding free space in relations
+ *
+ *
+ * Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * $Id: freespace.h,v 1.1 2001/06/27 23:31:39 tgl Exp $
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef FREESPACE_H_
+#define FREESPACE_H_
+
+#include "storage/block.h"
+#include "storage/relfilenode.h"
+#include "storage/spin.h"
+
+
+extern SPINLOCK FreeSpaceLock;
+
+extern int	MaxFSMRelations;
+extern int	MaxFSMPages;
+
+
+/*
+ * function prototypes
+ */
+extern void InitFreeSpaceMap(void);
+extern int	FreeSpaceShmemSize(void);
+
+extern BlockNumber GetPageWithFreeSpace(RelFileNode *rel, Size spaceNeeded);
+extern void RecordFreeSpace(RelFileNode *rel, BlockNumber page,
+							Size spaceAvail);
+extern BlockNumber RecordAndGetPageWithFreeSpace(RelFileNode *rel,
+												 BlockNumber oldPage,
+												 Size oldSpaceAvail,
+												 Size spaceNeeded);
+extern void MultiRecordFreeSpace(RelFileNode *rel,
+								 BlockNumber minPage,
+								 BlockNumber maxPage,
+								 int nPages,
+								 BlockNumber *pages,
+								 Size *spaceAvail);
+extern void FreeSpaceMapForgetRel(RelFileNode *rel);
+
+#ifdef FREESPACE_DEBUG
+extern void DumpFreeSpace(void);
+#endif
+
+#endif	 /* FREESPACE_H */