diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c
index 8b0c826aaf..49bca5b329 100644
--- a/src/backend/access/heap/heapam.c
+++ b/src/backend/access/heap/heapam.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/access/heap/heapam.c,v 1.267 2008/10/31 15:04:59 heikki Exp $
+ *	  $PostgreSQL: pgsql/src/backend/access/heap/heapam.c,v 1.268 2008/10/31 19:40:26 heikki Exp $
  *
  *
  * INTERFACE ROUTINES
@@ -54,6 +54,7 @@
 #include "miscadmin.h"
 #include "pgstat.h"
 #include "storage/bufmgr.h"
+#include "storage/freespace.h"
 #include "storage/lmgr.h"
 #include "storage/procarray.h"
 #include "storage/smgr.h"
@@ -4022,6 +4023,7 @@ heap_xlog_clean(XLogRecPtr lsn, XLogRecord *record, bool clean_move)
 	int			nredirected;
 	int			ndead;
 	int			nunused;
+	Size		freespace;
 
 	if (record->xl_info & XLR_BKP_BLOCK_1)
 		return;
@@ -4053,6 +4055,8 @@ heap_xlog_clean(XLogRecPtr lsn, XLogRecord *record, bool clean_move)
 							nowunused, nunused,
 							clean_move);
 
+	freespace = PageGetHeapFreeSpace(page); /* needed to update FSM below */
+
 	/*
 	 * Note: we don't worry about updating the page's prunability hints.
 	 * At worst this will cause an extra prune cycle to occur soon.
@@ -4062,6 +4066,15 @@ heap_xlog_clean(XLogRecPtr lsn, XLogRecord *record, bool clean_move)
 	PageSetTLI(page, ThisTimeLineID);
 	MarkBufferDirty(buffer);
 	UnlockReleaseBuffer(buffer);
+
+	/*
+	 * Update the FSM as well.
+	 *
+	 * XXX: We don't get here if the page was restored from full page image.
+	 * We don't bother to update the FSM in that case, it doesn't need to be
+	 * totally accurate anyway.
+	 */
+	XLogRecordPageWithFreeSpace(xlrec->node, xlrec->block, freespace);
 }
 
 static void
@@ -4205,15 +4218,17 @@ heap_xlog_insert(XLogRecPtr lsn, XLogRecord *record)
 	HeapTupleHeader htup;
 	xl_heap_header xlhdr;
 	uint32		newlen;
+	Size		freespace;
+	BlockNumber	blkno;
 
 	if (record->xl_info & XLR_BKP_BLOCK_1)
 		return;
 
+	blkno = ItemPointerGetBlockNumber(&(xlrec->target.tid));
+
 	if (record->xl_info & XLOG_HEAP_INIT_PAGE)
 	{
-		buffer = XLogReadBuffer(xlrec->target.node,
-							 ItemPointerGetBlockNumber(&(xlrec->target.tid)),
-								true);
+		buffer = XLogReadBuffer(xlrec->target.node, blkno, true);
 		Assert(BufferIsValid(buffer));
 		page = (Page) BufferGetPage(buffer);
 
@@ -4221,9 +4236,7 @@ heap_xlog_insert(XLogRecPtr lsn, XLogRecord *record)
 	}
 	else
 	{
-		buffer = XLogReadBuffer(xlrec->target.node,
-							 ItemPointerGetBlockNumber(&(xlrec->target.tid)),
-								false);
+		buffer = XLogReadBuffer(xlrec->target.node, blkno, false);
 		if (!BufferIsValid(buffer))
 			return;
 		page = (Page) BufferGetPage(buffer);
@@ -4261,10 +4274,25 @@ heap_xlog_insert(XLogRecPtr lsn, XLogRecord *record)
 	offnum = PageAddItem(page, (Item) htup, newlen, offnum, true, true);
 	if (offnum == InvalidOffsetNumber)
 		elog(PANIC, "heap_insert_redo: failed to add tuple");
+
+	freespace = PageGetHeapFreeSpace(page); /* needed to update FSM below */
+
 	PageSetLSN(page, lsn);
 	PageSetTLI(page, ThisTimeLineID);
 	MarkBufferDirty(buffer);
 	UnlockReleaseBuffer(buffer);
+
+	/*
+	 * If the page is running low on free space, update the FSM as well.
+	 * Arbitrarily, our definition of "low" is less than 20%. We can't do
+	 * much better than that without knowing the fill-factor for the table.
+	 *
+	 * XXX: We don't get here if the page was restored from full page image.
+	 * We don't bother to update the FSM in that case, it doesn't need to be
+	 * totally accurate anyway.
+	 */
+	if (freespace < BLCKSZ / 5)
+		XLogRecordPageWithFreeSpace(xlrec->target.node, blkno, freespace);
 }
 
 /*
@@ -4289,6 +4317,7 @@ heap_xlog_update(XLogRecPtr lsn, XLogRecord *record, bool move, bool hot_update)
 	xl_heap_header xlhdr;
 	int			hsize;
 	uint32		newlen;
+	Size		freespace;
 
 	if (record->xl_info & XLR_BKP_BLOCK_1)
 	{
@@ -4446,10 +4475,32 @@ newsame:;
 	offnum = PageAddItem(page, (Item) htup, newlen, offnum, true, true);
 	if (offnum == InvalidOffsetNumber)
 		elog(PANIC, "heap_update_redo: failed to add tuple");
+
+	freespace = PageGetHeapFreeSpace(page); /* needed to update FSM below */
+
 	PageSetLSN(page, lsn);
 	PageSetTLI(page, ThisTimeLineID);
 	MarkBufferDirty(buffer);
 	UnlockReleaseBuffer(buffer);
+
+	/*
+	 * If the page is running low on free space, update the FSM as well.
+	 * Arbitrarily, our definition of "low" is less than 20%. We can't do
+	 * much better than that without knowing the fill-factor for the table.
+	 *
+	 * However, don't update the FSM on HOT updates, because after crash
+	 * recovery, either the old or the new tuple will certainly be dead and
+	 * prunable. After pruning, the page will have roughly as much free space
+	 * as it did before the update, assuming the new tuple is about the same
+	 * size as the old one.
+	 *
+	 * XXX: We don't get here if the page was restored from full page image.
+	 * We don't bother to update the FSM in that case, it doesn't need to be
+	 * totally accurate anyway.
+	 */
+	if (!hot_update && freespace < BLCKSZ / 5)
+		XLogRecordPageWithFreeSpace(xlrec->target.node,
+					ItemPointerGetBlockNumber(&(xlrec->newtid)), freespace);
 }
 
 static void
diff --git a/src/backend/storage/freespace/freespace.c b/src/backend/storage/freespace/freespace.c
index 724e87fa20..10cca029d1 100644
--- a/src/backend/storage/freespace/freespace.c
+++ b/src/backend/storage/freespace/freespace.c
@@ -8,7 +8,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/storage/freespace/freespace.c,v 1.65 2008/10/31 15:05:00 heikki Exp $
+ *	  $PostgreSQL: pgsql/src/backend/storage/freespace/freespace.c,v 1.66 2008/10/31 19:40:27 heikki Exp $
  *
  *
  * NOTES:
@@ -202,6 +202,36 @@ RecordPageWithFreeSpace(Relation rel, BlockNumber heapBlk, Size spaceAvail)
 	fsm_set_and_search(rel, addr, slot, new_cat, 0);
 }
 
+/*
+ * XLogRecordPageWithFreeSpace - like RecordPageWithFreeSpace, for use in
+ *		WAL replay
+ */
+void
+XLogRecordPageWithFreeSpace(RelFileNode rnode, BlockNumber heapBlk,
+							Size spaceAvail)
+{
+	int			new_cat = fsm_space_avail_to_cat(spaceAvail);
+	FSMAddress	addr;
+	uint16		slot;
+	BlockNumber blkno;
+	Buffer		buf;
+	Page		page;
+
+	/* Get the location of the FSM byte representing the heap block */
+	addr = fsm_get_location(heapBlk, &slot);
+	blkno = fsm_logical_to_physical(addr);
+
+	/* If the page doesn't exist already, extend */
+	buf = XLogReadBufferExtended(rnode, FSM_FORKNUM, blkno, RBM_ZERO_ON_ERROR);
+	page = BufferGetPage(buf);
+	if (PageIsNew(page))
+		PageInit(page, BLCKSZ, 0);
+
+	if (fsm_set_avail(page, slot, new_cat))
+		MarkBufferDirty(buf);
+	UnlockReleaseBuffer(buf);
+}
+
 /*
  * GetRecordedFreePage - return the amount of free space on a particular page,
  *		according to the FSM.
diff --git a/src/include/storage/freespace.h b/src/include/storage/freespace.h
index d417e8c980..858be59528 100644
--- a/src/include/storage/freespace.h
+++ b/src/include/storage/freespace.h
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/storage/freespace.h,v 1.29 2008/09/30 10:52:13 heikki Exp $
+ * $PostgreSQL: pgsql/src/include/storage/freespace.h,v 1.30 2008/10/31 19:40:27 heikki Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -27,6 +27,8 @@ extern BlockNumber RecordAndGetPageWithFreeSpace(Relation rel,
 							  Size spaceNeeded);
 extern void RecordPageWithFreeSpace(Relation rel, BlockNumber heapBlk,
 									Size spaceAvail);
+extern void XLogRecordPageWithFreeSpace(RelFileNode rnode, BlockNumber heapBlk,
+										Size spaceAvail);
 
 extern void FreeSpaceMapTruncateRel(Relation rel, BlockNumber nblocks);
 extern void FreeSpaceMapVacuum(Relation rel);