First non-stub implementation of shared free space map. It's not super

useful as yet, since its primary source of information is (full) VACUUM,
which makes a concerted effort to get rid of free space before telling
the map about it ... next stop is concurrent VACUUM ...

src/backend/commands/dbcommands.c

@@ -9,7 +9,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/commands/dbcommands.c,v 1.75 2001/06/12 05:55:49 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/commands/dbcommands.c,v 1.76 2001/07/02 20:50:46 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -30,7 +30,8 @@
 #include "commands/comment.h"
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
-#include "storage/sinval.h"		/* for DatabaseHasActiveBackends */
+#include "storage/freespace.h"
+#include "storage/sinval.h"
 #include "utils/builtins.h"
 #include "utils/fmgroids.h"
 #include "utils/syscache.h"
@@ -372,6 +373,11 @@ dropdb(const char *dbname)
 	 */
 	DropBuffers(db_id);
 
+	/*
+	 * Also, clean out any entries in the shared free space map.
+	 */
+	FreeSpaceMapForgetDatabase(db_id);
+
 	/*
 	 * Remove the database's subdirectory and everything in it.
 	 */

src/backend/commands/vacuum.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/commands/vacuum.c,v 1.200 2001/06/29 20:14:27 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/commands/vacuum.c,v 1.201 2001/07/02 20:50:46 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -37,6 +37,7 @@
 #include "commands/vacuum.h"
 #include "miscadmin.h"
 #include "nodes/execnodes.h"
+#include "storage/freespace.h"
 #include "storage/sinval.h"
 #include "storage/smgr.h"
 #include "tcop/tcopprot.h"
@@ -146,6 +147,8 @@ static void vacuum_index(VacPageList vacpagelist, Relation indrel,
 						 double num_tuples, int keep_tuples);
 static void scan_index(Relation indrel, double num_tuples);
 static VacPage tid_reaped(ItemPointer itemptr, VacPageList vacpagelist);
+static void vac_update_fsm(Relation onerel, VacPageList fraged_pages,
+						   BlockNumber rel_pages);
 static VacPage copy_vac_page(VacPage vacpage);
 static void vpage_insert(VacPageList vacpagelist, VacPage vpnew);
 static void get_indices(Relation relation, int *nindices, Relation **Irel);
@@ -579,6 +582,9 @@ vacuum_rel(Oid relid)
 		activate_indexes_of_a_table(relid, true);
 #endif	 /* NOT_USED */
 
+	/* update shared free space map with final free space info */
+	vac_update_fsm(onerel, &fraged_pages, vacrelstats->rel_pages);
+
 	/* all done with this class, but hold lock until commit */
 	heap_close(onerel, NoLock);
 
@@ -1157,6 +1163,10 @@ repair_frag(VRelStats *vacrelstats, Relation onerel,
 		 * useful as move targets, since we only want to move down.  Note
 		 * that since we stop the outer loop at last_move_dest_block, pages
 		 * removed here cannot have had anything moved onto them already.
+		 *
+		 * Also note that we don't change the stored fraged_pages list,
+		 * only our local variable num_fraged_pages; so the forgotten pages
+		 * are still available to be loaded into the free space map later.
 		 */
 		while (num_fraged_pages > 0 &&
 			   fraged_pages->pagedesc[num_fraged_pages-1]->blkno >= blkno)
@@ -2080,6 +2090,8 @@ repair_frag(VRelStats *vacrelstats, Relation onerel,
 	if (blkno < nblocks)
 	{
 		blkno = smgrtruncate(DEFAULT_SMGR, onerel, blkno);
+		onerel->rd_nblocks = blkno;	/* update relcache immediately */
+		onerel->rd_targblock = InvalidBlockNumber;
 		vacrelstats->rel_pages = blkno; /* set new number of blocks */
 	}
 
@@ -2145,6 +2157,8 @@ vacuum_heap(VRelStats *vacrelstats, Relation onerel, VacPageList vacuum_pages)
 			 RelationGetRelationName(onerel),
 			 vacrelstats->rel_pages, relblocks);
 		relblocks = smgrtruncate(DEFAULT_SMGR, onerel, relblocks);
+		onerel->rd_nblocks = relblocks;	/* update relcache immediately */
+		onerel->rd_targblock = InvalidBlockNumber;
 		vacrelstats->rel_pages = relblocks;		/* set new number of
 												 * blocks */
 	}
@@ -2414,6 +2428,45 @@ vac_update_relstats(Oid relid, BlockNumber num_pages, double num_tuples,
 	heap_close(rd, RowExclusiveLock);
 }
 
+/*
+ * Update the shared Free Space Map with the info we now have about
+ * free space in the relation, discarding any old info the map may have.
+ */
+static void
+vac_update_fsm(Relation onerel, VacPageList fraged_pages,
+			   BlockNumber rel_pages)
+{
+	int			nPages = fraged_pages->num_pages;
+	int			i;
+	BlockNumber *pages;
+	Size	   *spaceAvail;
+
+	/* +1 to avoid palloc(0) */
+	pages = (BlockNumber *) palloc((nPages + 1) * sizeof(BlockNumber));
+	spaceAvail = (Size *) palloc((nPages + 1) * sizeof(Size));
+
+	for (i = 0; i < nPages; i++)
+	{
+		pages[i] = fraged_pages->pagedesc[i]->blkno;
+		spaceAvail[i] = fraged_pages->pagedesc[i]->free;
+		/*
+		 * fraged_pages may contain entries for pages that we later decided
+		 * to truncate from the relation; don't enter them into the map!
+		 */
+		if (pages[i] >= rel_pages)
+		{
+			nPages = i;
+			break;
+		}
+	}
+
+	MultiRecordFreeSpace(&onerel->rd_node,
+						 0, MaxBlockNumber,
+						 nPages, pages, spaceAvail);
+	pfree(pages);
+	pfree(spaceAvail);
+}
+
 /* Copy a VacPage structure */
 static VacPage
 copy_vac_page(VacPage vacpage)

src/backend/storage/smgr/smgr.c

@@ -11,7 +11,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/storage/smgr/smgr.c,v 1.51 2001/06/29 21:08:24 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/storage/smgr/smgr.c,v 1.52 2001/07/02 20:50:46 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -469,11 +469,13 @@ smgrtruncate(int16 which, Relation reln, BlockNumber nblocks)
 	if (smgrsw[which].smgr_truncate)
 	{
 		/*
-		 * Tell the free space map to forget this relation, so that it
-		 * stops caching info about the deleted blocks.  XXX perhaps
-		 * tell it to forget only info about blocks beyond nblocks?
+		 * Tell the free space map to forget anything it may have stored
+		 * for the about-to-be-deleted blocks.  We want to be sure it won't
+		 * return bogus block numbers later on.
 		 */
-		FreeSpaceMapForgetRel(&reln->rd_node);
+		MultiRecordFreeSpace(&reln->rd_node,
+							 nblocks, MaxBlockNumber,
+							 0, NULL, NULL);
 
 		newblks = (*(smgrsw[which].smgr_truncate)) (reln, nblocks);
 		if (newblks == InvalidBlockNumber)

src/include/storage/block.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Id: block.h,v 1.12 2001/01/24 19:43:27 momjian Exp $
+ * $Id: block.h,v 1.13 2001/07/02 20:50:46 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -32,6 +32,8 @@ typedef uint32 BlockNumber;
 
 #define InvalidBlockNumber		((BlockNumber) 0xFFFFFFFF)
 
+#define MaxBlockNumber			((BlockNumber) 0xFFFFFFFE)
+
 /*
  * BlockId:
  *

src/include/storage/freespace.h

@@ -7,7 +7,7 @@
  * 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 $
+ * $Id: freespace.h,v 1.2 2001/07/02 20:50:46 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -45,6 +45,7 @@ extern void MultiRecordFreeSpace(RelFileNode *rel,
 								 BlockNumber *pages,
 								 Size *spaceAvail);
 extern void FreeSpaceMapForgetRel(RelFileNode *rel);
+extern void FreeSpaceMapForgetDatabase(Oid dbid);
 
 #ifdef FREESPACE_DEBUG
 extern void DumpFreeSpace(void);