FSM RGMR

src/backend/access/heap/heapam_xlog.c

@@ -147,26 +147,9 @@ heap_xlog_prune_freeze(XLogReaderState *record)
 		MarkBufferDirty(buffer);
 	}
 
-	/*
-	 * If we released any space or line pointers, update the free space map.
-	 *
-	 * Do this regardless of a full-page image being applied, since the FSM
-	 * data is not in the page anyway.
-	 */
 	if (BufferIsValid(buffer))
 	{
-		if (xlrec.flags & (XLHP_HAS_REDIRECTIONS |
-						   XLHP_HAS_DEAD_ITEMS |
-						   XLHP_HAS_NOW_UNUSED_ITEMS))
-		{
-			Size		freespace = PageGetHeapFreeSpace(BufferGetPage(buffer));
-
-			UnlockReleaseBuffer(buffer);
-
-			XLogRecordPageWithFreeSpace(rlocator, blkno, freespace);
-		}
-		else
-			UnlockReleaseBuffer(buffer);
+		UnlockReleaseBuffer(buffer);
 	}
 }
 
@@ -246,26 +229,6 @@ heap_xlog_visible(XLogReaderState *record)
 		Size		space = PageGetFreeSpace(BufferGetPage(buffer));
 
 		UnlockReleaseBuffer(buffer);
-
-		/*
-		 * Since FSM is not WAL-logged and only updated heuristically, it
-		 * easily becomes stale in standbys.  If the standby is later promoted
-		 * and runs VACUUM, it will skip updating individual free space
-		 * figures for pages that became all-visible (or all-frozen, depending
-		 * on the vacuum mode,) which is troublesome when FreeSpaceMapVacuum
-		 * propagates too optimistic free space values to upper FSM layers;
-		 * later inserters try to use such pages only to find out that they
-		 * are unusable.  This can cause long stalls when there are many such
-		 * pages.
-		 *
-		 * Forestall those problems by updating FSM's idea about a page that
-		 * is becoming all-visible or all-frozen.
-		 *
-		 * Do this regardless of a full-page image being applied, since the
-		 * FSM data is not in the page anyway.
-		 */
-		if (xlrec->flags & VISIBILITYMAP_VALID_BITS)
-			XLogRecordPageWithFreeSpace(rlocator, blkno, space);
 	}
 
 	/*
@@ -515,18 +478,6 @@ heap_xlog_insert(XLogReaderState *record)
 	}
 	if (BufferIsValid(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: Don't do this 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 (action == BLK_NEEDS_REDO && freespace < BLCKSZ / 5)
-		XLogRecordPageWithFreeSpace(target_locator, blkno, freespace);
 }
 
 /*
@@ -662,18 +613,6 @@ heap_xlog_multi_insert(XLogReaderState *record)
 	}
 	if (BufferIsValid(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: Don't do this 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 (action == BLK_NEEDS_REDO && freespace < BLCKSZ / 5)
-		XLogRecordPageWithFreeSpace(rlocator, blkno, freespace);
 }
 
 /*
@@ -931,24 +870,6 @@ heap_xlog_update(XLogReaderState *record, bool hot_update)
 		UnlockReleaseBuffer(nbuffer);
 	if (BufferIsValid(obuffer))
 		UnlockReleaseBuffer(obuffer);
-
-	/*
-	 * If the new 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: Don't do this 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 (newaction == BLK_NEEDS_REDO && !hot_update && freespace < BLCKSZ / 5)
-		XLogRecordPageWithFreeSpace(rlocator, newblk, freespace);
 }
 
 /*

src/backend/access/rmgrdesc/Makefile

@@ -13,6 +13,7 @@ OBJS = \
 	clogdesc.o \
 	committsdesc.o \
 	dbasedesc.o \
+	fsmdesc.o \
 	genericdesc.o \
 	gindesc.o \
 	gistdesc.o \

src/backend/access/rmgrdesc/fsmdesc.c

@@ -0,0 +1,48 @@
+/*-------------------------------------------------------------------------
+ *
+ * fsmdesc.c
+ *	  rmgr descriptor routines for storage/freespace/freespace.c
+ *
+ *
+ * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/backend/access/rmgrdesc/fsmdesc.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "access/fsm_xlog.h"
+#include "lib/stringinfo.h"
+
+
+const char *
+fsm_identify(uint8 info)
+{
+	if ((info & ~XLR_INFO_MASK) == XLOG_FSM_UPDATE)
+		return "FSM_UPDATE";
+
+	return NULL;
+}
+
+void
+fsm_desc(StringInfo buf, XLogReaderState *record)
+{
+	int			i;
+	char	   *rec = XLogRecGetData(record);
+	uint8		info = XLogRecGetInfo(record) & ~XLR_INFO_MASK;
+
+	if (info == XLOG_FSM_UPDATE)
+	{
+		xl_fsm_update *xlrec = (xl_fsm_update *) rec;
+
+		appendStringInfo(buf, "nevent: %d ", xlrec->nchanges);
+
+		for (i = 0; i < xlrec->nchanges; ++i)
+		{
+			appendStringInfo(buf, ", offset %d value %d", xlrec->ev[2 * i], xlrec->ev[2 * i + 1]);
+		}
+	}
+}
+

src/backend/access/rmgrdesc/meson.build

@@ -6,6 +6,7 @@ rmgr_desc_sources = files(
   'clogdesc.c',
   'committsdesc.c',
   'dbasedesc.c',
+  'fsmdesc.c',
   'genericdesc.c',
   'gindesc.c',
   'gistdesc.c',

src/backend/access/transam/rmgr.c

@@ -22,6 +22,7 @@
 #include "access/brin_xlog.h"
 #include "access/clog.h"
 #include "access/commit_ts.h"
+#include "access/fsm_xlog.h"
 #include "access/generic_xlog.h"
 #include "access/ginxlog.h"
 #include "access/gistxlog.h"