Revert "Avoid creation of the free space map for small heap relations."

This reverts commit ac88d296.

contrib/pageinspect/expected/page.out

 CREATE EXTENSION pageinspect;
-CREATE TABLE test_rel_forks (a int);
--- Make sure there are enough blocks in the heap for the FSM to be created.
-INSERT INTO test_rel_forks SELECT i from generate_series(1,1000) i;
--- set up FSM and VM
-VACUUM test_rel_forks;
+CREATE TABLE test1 (a int, b int);
+INSERT INTO test1 VALUES (16777217, 131584);
+VACUUM test1;  -- set up FSM
 -- The page contents can vary, so just test that it can be read
 -- successfully, but don't keep the output.
-SELECT octet_length(get_raw_page('test_rel_forks', 'main', 0)) AS main_0;
+SELECT octet_length(get_raw_page('test1', 'main', 0)) AS main_0;
  main_0 
 --------
    8192
 (1 row)
 
-SELECT octet_length(get_raw_page('test_rel_forks', 'main', 100)) AS main_100;
-ERROR:  block number 100 is out of range for relation "test_rel_forks"
-SELECT octet_length(get_raw_page('test_rel_forks', 'fsm', 0)) AS fsm_0;
+SELECT octet_length(get_raw_page('test1', 'main', 1)) AS main_1;
+ERROR:  block number 1 is out of range for relation "test1"
+SELECT octet_length(get_raw_page('test1', 'fsm', 0)) AS fsm_0;
  fsm_0 
 -------
   8192
 (1 row)
 
-SELECT octet_length(get_raw_page('test_rel_forks', 'fsm', 10)) AS fsm_10;
-ERROR:  block number 10 is out of range for relation "test_rel_forks"
-SELECT octet_length(get_raw_page('test_rel_forks', 'vm', 0)) AS vm_0;
+SELECT octet_length(get_raw_page('test1', 'fsm', 1)) AS fsm_1;
+ fsm_1 
+-------
+  8192
+(1 row)
+
+SELECT octet_length(get_raw_page('test1', 'vm', 0)) AS vm_0;
  vm_0 
 ------
  8192
 (1 row)
 
-SELECT octet_length(get_raw_page('test_rel_forks', 'vm', 1)) AS vm_1;
-ERROR:  block number 1 is out of range for relation "test_rel_forks"
+SELECT octet_length(get_raw_page('test1', 'vm', 1)) AS vm_1;
+ERROR:  block number 1 is out of range for relation "test1"
 SELECT octet_length(get_raw_page('xxx', 'main', 0));
 ERROR:  relation "xxx" does not exist
-SELECT octet_length(get_raw_page('test_rel_forks', 'xxx', 0));
+SELECT octet_length(get_raw_page('test1', 'xxx', 0));
 ERROR:  invalid fork name
 HINT:  Valid fork names are "main", "fsm", "vm", and "init".
-SELECT * FROM fsm_page_contents(get_raw_page('test_rel_forks', 'fsm', 0));
- fsm_page_contents 
--------------------
- 0: 147           +
- 1: 147           +
- 3: 147           +
- 7: 147           +
- 15: 147          +
- 31: 147          +
- 63: 147          +
- 127: 147         +
- 255: 147         +
- 511: 147         +
- 1023: 147        +
- 2047: 147        +
- 4095: 147        +
- fp_next_slot: 0  +
- 
-(1 row)
-
-SELECT get_raw_page('test_rel_forks', 0) = get_raw_page('test_rel_forks', 'main', 0);
+SELECT get_raw_page('test1', 0) = get_raw_page('test1', 'main', 0);
  ?column? 
 ----------
  t
 (1 row)
 
-DROP TABLE test_rel_forks;
-CREATE TABLE test1 (a int, b int);
-INSERT INTO test1 VALUES (16777217, 131584);
 SELECT pagesize, version FROM page_header(get_raw_page('test1', 0));
  pagesize | version 
 ----------+---------
@@ -83,6 +62,26 @@ SELECT tuple_data_split('test1'::regclass, t_data, t_infomask, t_infomask2, t_bi
  {"\\x01000001","\\x00020200"}
 (1 row)
 
+SELECT * FROM fsm_page_contents(get_raw_page('test1', 'fsm', 0));
+ fsm_page_contents 
+-------------------
+ 0: 254           +
+ 1: 254           +
+ 3: 254           +
+ 7: 254           +
+ 15: 254          +
+ 31: 254          +
+ 63: 254          +
+ 127: 254         +
+ 255: 254         +
+ 511: 254         +
+ 1023: 254        +
+ 2047: 254        +
+ 4095: 254        +
+ fp_next_slot: 0  +
+ 
+(1 row)
+
 DROP TABLE test1;
 -- check that using any of these functions with a partitioned table or index
 -- would fail

contrib/pageinspect/sql/page.sql

 CREATE EXTENSION pageinspect;
 
-CREATE TABLE test_rel_forks (a int);
--- Make sure there are enough blocks in the heap for the FSM to be created.
-INSERT INTO test_rel_forks SELECT i from generate_series(1,1000) i;
+CREATE TABLE test1 (a int, b int);
+INSERT INTO test1 VALUES (16777217, 131584);
 
--- set up FSM and VM
-VACUUM test_rel_forks;
+VACUUM test1;  -- set up FSM
 
 -- The page contents can vary, so just test that it can be read
 -- successfully, but don't keep the output.
 
-SELECT octet_length(get_raw_page('test_rel_forks', 'main', 0)) AS main_0;
-SELECT octet_length(get_raw_page('test_rel_forks', 'main', 100)) AS main_100;
+SELECT octet_length(get_raw_page('test1', 'main', 0)) AS main_0;
+SELECT octet_length(get_raw_page('test1', 'main', 1)) AS main_1;
 
-SELECT octet_length(get_raw_page('test_rel_forks', 'fsm', 0)) AS fsm_0;
-SELECT octet_length(get_raw_page('test_rel_forks', 'fsm', 10)) AS fsm_10;
+SELECT octet_length(get_raw_page('test1', 'fsm', 0)) AS fsm_0;
+SELECT octet_length(get_raw_page('test1', 'fsm', 1)) AS fsm_1;
 
-SELECT octet_length(get_raw_page('test_rel_forks', 'vm', 0)) AS vm_0;
-SELECT octet_length(get_raw_page('test_rel_forks', 'vm', 1)) AS vm_1;
+SELECT octet_length(get_raw_page('test1', 'vm', 0)) AS vm_0;
+SELECT octet_length(get_raw_page('test1', 'vm', 1)) AS vm_1;
 
 SELECT octet_length(get_raw_page('xxx', 'main', 0));
-SELECT octet_length(get_raw_page('test_rel_forks', 'xxx', 0));
-
-SELECT * FROM fsm_page_contents(get_raw_page('test_rel_forks', 'fsm', 0));
-
-SELECT get_raw_page('test_rel_forks', 0) = get_raw_page('test_rel_forks', 'main', 0);
+SELECT octet_length(get_raw_page('test1', 'xxx', 0));
 
-DROP TABLE test_rel_forks;
-
-CREATE TABLE test1 (a int, b int);
-INSERT INTO test1 VALUES (16777217, 131584);
+SELECT get_raw_page('test1', 0) = get_raw_page('test1', 'main', 0);
 
 SELECT pagesize, version FROM page_header(get_raw_page('test1', 0));
 
@@ -38,6 +29,8 @@ SELECT page_checksum(get_raw_page('test1', 0), 0) IS NOT NULL AS silly_checksum_
 SELECT tuple_data_split('test1'::regclass, t_data, t_infomask, t_infomask2, t_bits)
     FROM heap_page_items(get_raw_page('test1', 0));
 
+SELECT * FROM fsm_page_contents(get_raw_page('test1', 'fsm', 0));
+
 DROP TABLE test1;
 
 -- check that using any of these functions with a partitioned table or index

doc/src/sgml/storage.sgml

@@ -590,13 +590,12 @@ tuple would otherwise be too big.
 <indexterm><primary>FSM</primary><see>Free Space Map</see></indexterm>
 
 <para>
-Each heap relation, unless it is very small, and each index relation, except
-for hash indexes, has a Free Space Map (FSM) to keep track of available
-space in the relation. It's stored alongside the main relation data in a
-separate relation fork, named after the filenode number of the relation, plus
-a <literal>_fsm</literal> suffix. For example, if the filenode of a relation
-is 12345, the FSM is stored in a file called <filename>12345_fsm</filename>,
-in the same directory as the main relation file.
+Each heap and index relation, except for hash indexes, has a Free Space Map
+(FSM) to keep track of available space in the relation. It's stored
+alongside the main relation data in a separate relation fork, named after the
+filenode number of the relation, plus a <literal>_fsm</literal> suffix. For example,
+if the filenode of a relation is 12345, the FSM is stored in a file called
+<filename>12345_fsm</filename>, in the same directory as the main relation file.
 </para>
 
 <para>

src/backend/access/brin/brin.c

@@ -1150,7 +1150,7 @@ terminate_brin_buildstate(BrinBuildState *state)
 		freespace = PageGetFreeSpace(page);
 		blk = BufferGetBlockNumber(state->bs_currentInsertBuf);
 		ReleaseBuffer(state->bs_currentInsertBuf);
-		RecordPageWithFreeSpace(state->bs_irel, blk, freespace, InvalidBlockNumber);
+		RecordPageWithFreeSpace(state->bs_irel, blk, freespace);
 		FreeSpaceMapVacuumRange(state->bs_irel, blk, blk + 1);
 	}
 

src/backend/access/brin/brin_pageops.c

@@ -310,7 +310,7 @@ brin_doupdate(Relation idxrel, BlockNumber pagesPerRange,
 
 		if (extended)
 		{
-			RecordPageWithFreeSpace(idxrel, newblk, freespace, InvalidBlockNumber);
+			RecordPageWithFreeSpace(idxrel, newblk, freespace);
 			FreeSpaceMapVacuumRange(idxrel, newblk, newblk + 1);
 		}
 
@@ -461,7 +461,7 @@ brin_doinsert(Relation idxrel, BlockNumber pagesPerRange,
 
 	if (extended)
 	{
-		RecordPageWithFreeSpace(idxrel, blk, freespace, InvalidBlockNumber);
+		RecordPageWithFreeSpace(idxrel, blk, freespace);
 		FreeSpaceMapVacuumRange(idxrel, blk, blk + 1);
 	}
 
@@ -654,7 +654,7 @@ brin_page_cleanup(Relation idxrel, Buffer buf)
 
 	/* Measure free space and record it */
 	RecordPageWithFreeSpace(idxrel, BufferGetBlockNumber(buf),
-							br_page_get_freespace(page), InvalidBlockNumber);
+							br_page_get_freespace(page));
 }
 
 /*
@@ -703,7 +703,7 @@ brin_getinsertbuffer(Relation irel, Buffer oldbuf, Size itemsz,
 	/* Choose initial target page, re-using existing target if known */
 	newblk = RelationGetTargetBlock(irel);
 	if (newblk == InvalidBlockNumber)
-		newblk = GetPageWithFreeSpace(irel, itemsz, true);
+		newblk = GetPageWithFreeSpace(irel, itemsz);
 
 	/*
 	 * Loop until we find a page with sufficient free space.  By the time we
@@ -895,7 +895,7 @@ brin_initialize_empty_new_buffer(Relation idxrel, Buffer buffer)
 	 * pages whose FSM records were forgotten in a crash.
 	 */
 	RecordPageWithFreeSpace(idxrel, BufferGetBlockNumber(buffer),
-							br_page_get_freespace(page), InvalidBlockNumber);
+							br_page_get_freespace(page));
 }
 
 

src/backend/access/heap/hio.c

@@ -239,14 +239,8 @@ RelationAddExtraBlocks(Relation relation, BulkInsertState bistate)
 		 * Immediately update the bottom level of the FSM.  This has a good
 		 * chance of making this page visible to other concurrently inserting
 		 * backends, and we want that to happen without delay.
-		 *
-		 * Since we know the table will end up with extraBlocks additional
-		 * pages, we pass the final number to avoid possible unnecessary
-		 * system calls and to make sure the FSM is created when we add the
-		 * first new page.
 		 */
-		RecordPageWithFreeSpace(relation, blockNum, freespace,
-								firstBlock + extraBlocks);
+		RecordPageWithFreeSpace(relation, blockNum, freespace);
 	}
 	while (--extraBlocks > 0);
 
@@ -383,9 +377,20 @@ RelationGetBufferForTuple(Relation relation, Size len,
 		 * We have no cached target page, so ask the FSM for an initial
 		 * target.
 		 */
-		targetBlock = GetPageWithFreeSpace(relation,
-										   len + saveFreeSpace,
-										   false);
+		targetBlock = GetPageWithFreeSpace(relation, len + saveFreeSpace);
+
+		/*
+		 * If the FSM knows nothing of the rel, try the last page before we
+		 * give up and extend.  This avoids one-tuple-per-page syndrome during
+		 * bootstrapping or in a recently-started system.
+		 */
+		if (targetBlock == InvalidBlockNumber)
+		{
+			BlockNumber nblocks = RelationGetNumberOfBlocks(relation);
+
+			if (nblocks > 0)
+				targetBlock = nblocks - 1;
+		}
 	}
 
 loop:
@@ -479,14 +484,6 @@ loop:
 		{
 			/* use this page as future insert target, too */
 			RelationSetTargetBlock(relation, targetBlock);
-
-			/*
-			 * In case we used an in-memory map of available blocks, reset it
-			 * for next use.
-			 */
-			if (targetBlock < HEAP_FSM_CREATION_THRESHOLD)
-				FSMClearLocalMap();
-
 			return buffer;
 		}
 
@@ -546,12 +543,9 @@ loop:
 
 			/*
 			 * Check if some other backend has extended a block for us while
-			 * we were waiting on the lock.  We only check the FSM -- if there
-			 * isn't one we don't recheck the number of blocks.
+			 * we were waiting on the lock.
 			 */
-			targetBlock = GetPageWithFreeSpace(relation,
-											   len + saveFreeSpace,
-											   true);
+			targetBlock = GetPageWithFreeSpace(relation, len + saveFreeSpace);
 
 			/*
 			 * If some other waiter has already extended the relation, we
@@ -631,12 +625,5 @@ loop:
 	 */
 	RelationSetTargetBlock(relation, BufferGetBlockNumber(buffer));
 
-	/*
-	 * In case we used an in-memory map of available blocks, reset it for next
-	 * use.  We do this unconditionally since after relation extension we
-	 * can't skip this based on the targetBlock.
-	 */
-	FSMClearLocalMap();
-
 	return buffer;
 }

src/backend/access/heap/vacuumlazy.c

@@ -153,7 +153,7 @@ static BufferAccessStrategy vac_strategy;
 static void lazy_scan_heap(Relation onerel, int options,
 			   LVRelStats *vacrelstats, Relation *Irel, int nindexes,
 			   bool aggressive);
-static void lazy_vacuum_heap(Relation onerel, LVRelStats *vacrelstats, BlockNumber nblocks);
+static void lazy_vacuum_heap(Relation onerel, LVRelStats *vacrelstats);
 static bool lazy_check_needs_freeze(Buffer buf, bool *hastup);
 static void lazy_vacuum_index(Relation indrel,
 				  IndexBulkDeleteResult **stats,
@@ -758,7 +758,7 @@ lazy_scan_heap(Relation onerel, int options, LVRelStats *vacrelstats,
 			pgstat_progress_update_multi_param(2, hvp_index, hvp_val);
 
 			/* Remove tuples from heap */
-			lazy_vacuum_heap(onerel, vacrelstats, nblocks);
+			lazy_vacuum_heap(onerel, vacrelstats);
 
 			/*
 			 * Forget the now-vacuumed tuples, and press on, but be careful
@@ -896,7 +896,7 @@ lazy_scan_heap(Relation onerel, int options, LVRelStats *vacrelstats,
 			MarkBufferDirty(buf);
 			UnlockReleaseBuffer(buf);
 
-			RecordPageWithFreeSpace(onerel, blkno, freespace, nblocks);
+			RecordPageWithFreeSpace(onerel, blkno, freespace);
 			continue;
 		}
 
@@ -935,7 +935,7 @@ lazy_scan_heap(Relation onerel, int options, LVRelStats *vacrelstats,
 			}
 
 			UnlockReleaseBuffer(buf);
-			RecordPageWithFreeSpace(onerel, blkno, freespace, nblocks);
+			RecordPageWithFreeSpace(onerel, blkno, freespace);
 			continue;
 		}
 
@@ -1332,7 +1332,7 @@ lazy_scan_heap(Relation onerel, int options, LVRelStats *vacrelstats,
 		 * taken if there are no indexes.)
 		 */
 		if (vacrelstats->num_dead_tuples == prev_dead_count)
-			RecordPageWithFreeSpace(onerel, blkno, freespace, nblocks);
+			RecordPageWithFreeSpace(onerel, blkno, freespace);
 	}
 
 	/* report that everything is scanned and vacuumed */
@@ -1394,7 +1394,7 @@ lazy_scan_heap(Relation onerel, int options, LVRelStats *vacrelstats,
 		/* Remove tuples from heap */
 		pgstat_progress_update_param(PROGRESS_VACUUM_PHASE,
 									 PROGRESS_VACUUM_PHASE_VACUUM_HEAP);
-		lazy_vacuum_heap(onerel, vacrelstats, nblocks);
+		lazy_vacuum_heap(onerel, vacrelstats);
 		vacrelstats->num_index_scans++;
 	}
 
@@ -1465,10 +1465,9 @@ lazy_scan_heap(Relation onerel, int options, LVRelStats *vacrelstats,
  * Note: the reason for doing this as a second pass is we cannot remove
  * the tuples until we've removed their index entries, and we want to
  * process index entry removal in batches as large as possible.
- * Note: nblocks is passed as an optimization for RecordPageWithFreeSpace().
  */
 static void
-lazy_vacuum_heap(Relation onerel, LVRelStats *vacrelstats, BlockNumber nblocks)
+lazy_vacuum_heap(Relation onerel, LVRelStats *vacrelstats)
 {
 	int			tupindex;
 	int			npages;
@@ -1505,7 +1504,7 @@ lazy_vacuum_heap(Relation onerel, LVRelStats *vacrelstats, BlockNumber nblocks)
 		freespace = PageGetHeapFreeSpace(page);
 
 		UnlockReleaseBuffer(buf);
-		RecordPageWithFreeSpace(onerel, tblk, freespace, nblocks);
+		RecordPageWithFreeSpace(onerel, tblk, freespace);
 		npages++;
 	}
 

src/backend/access/transam/xact.c

@@ -48,7 +48,6 @@
 #include "replication/walsender.h"
 #include "storage/condition_variable.h"
 #include "storage/fd.h"
-#include "storage/freespace.h"
 #include "storage/lmgr.h"
 #include "storage/predicate.h"
 #include "storage/proc.h"
@@ -2494,12 +2493,6 @@ AbortTransaction(void)
 	pgstat_report_wait_end();
 	pgstat_progress_end_command();
 
-	/*
-	 * In case we aborted during RelationGetBufferForTuple(), clear the local
-	 * map of heap pages.
-	 */
-	FSMClearLocalMap();
-
 	/* Clean up buffer I/O and buffer context locks, too */
 	AbortBufferIO();
 	UnlockBuffers();
@@ -4721,13 +4714,6 @@ AbortSubTransaction(void)
 
 	pgstat_report_wait_end();
 	pgstat_progress_end_command();
-
-	/*
-	 * In case we aborted during RelationGetBufferForTuple(), clear the local
-	 * map of heap pages.
-	 */
-	FSMClearLocalMap();
-
 	AbortBufferIO();
 	UnlockBuffers();
 

src/backend/storage/freespace/README

@@ -8,41 +8,7 @@ free space to hold a tuple to be stored; or to determine that no such page
 exists and the relation must be extended by one page.  As of PostgreSQL 8.4
 each relation has its own, extensible free space map stored in a separate
 "fork" of its relation.  This eliminates the disadvantages of the former
-fixed-size FSM.  There are two exceptions:
-
-1. Hash indexes never have a FSM.
-2. For very small tables, a 3-page relation fork would be relatively large
-and wasteful, so to save space we refrain from creating the FSM if the
-heap has HEAP_FSM_CREATION_THRESHOLD pages or fewer.
-
-To locate free space in the latter case, we simply try pages directly without
-knowing ahead of time how much free space they have.  To maintain good
-performance, we create a local in-memory map of pages to try, and only mark
-every other page as available.  For example, in a 3-page heap, the local map
-would look like:
-
-ANAN
-0123
-
-Pages 0 and 2 are marked "available", and page 1 as "not available".
-Page 3 is beyond the end of the relation, so is likewise marked "not
-available".  First we try page 2, and if that doesn't have sufficient free
-space we try page 0 before giving up and extending the relation.  There may
-be some wasted free space on block 1, but if the relation extends to 4 pages:
-
-NANA
-0123
-
-We not only have the new page 3 at our disposal, we can now check page 1
-for free space as well.
-
-Once the FSM is created for a heap we don't remove it even if somebody deletes
-all the rows from the corresponding relation.  We don't think it is a useful
-optimization as it is quite likely that relation will again grow to the same
-size.
-
-FSM data structure
-------------------
+fixed-size FSM.
 
 It is important to keep the map small so that it can be searched rapidly.
 Therefore, we don't attempt to record the exact free space on a page.
@@ -226,3 +192,5 @@ TODO
 ----
 
 - fastroot to avoid traversing upper nodes with just 1 child
+- use a different system for tables that fit into one FSM page, with a
+  mechanism to switch to the real thing as it grows.

src/backend/storage/freespace/freespace.c

@@ -76,14 +76,6 @@
 #define FSM_ROOT_LEVEL	(FSM_TREE_DEPTH - 1)
 #define FSM_BOTTOM_LEVEL 0
 
-/* Status codes for the local map. */
-
-/* Either already tried, or beyond the end of the relation */
-#define FSM_LOCAL_NOT_AVAIL 0x00
-
-/* Available to try */
-#define FSM_LOCAL_AVAIL		0x01
-
 /*
  * The internal FSM routines work on a logical addressing scheme. Each
  * level of the tree can be thought of as a separately addressable file.
@@ -97,17 +89,6 @@ typedef struct
 /* Address of the root page. */
 static const FSMAddress FSM_ROOT_ADDRESS = {FSM_ROOT_LEVEL, 0};
 
-/* Local map of block numbers for small heaps with no FSM. */
-typedef struct
-{
-	BlockNumber nblocks;
-	uint8		map[HEAP_FSM_CREATION_THRESHOLD];
-} FSMLocalMap;
-
-static FSMLocalMap fsm_local_map = {0, {FSM_LOCAL_NOT_AVAIL}};
-
-#define FSM_LOCAL_MAP_EXISTS (fsm_local_map.nblocks > 0)
-
 /* functions to navigate the tree */
 static FSMAddress fsm_get_child(FSMAddress parent, uint16 slot);
 static FSMAddress fsm_get_parent(FSMAddress child, uint16 *slot);
@@ -126,14 +107,10 @@ static Size fsm_space_cat_to_avail(uint8 cat);
 /* workhorse functions for various operations */
 static int fsm_set_and_search(Relation rel, FSMAddress addr, uint16 slot,
 				   uint8 newValue, uint8 minValue);
-static void fsm_local_set(Relation rel, BlockNumber cur_nblocks);
 static BlockNumber fsm_search(Relation rel, uint8 min_cat);
-static BlockNumber fsm_local_search(void);
 static uint8 fsm_vacuum_page(Relation rel, FSMAddress addr,
 				BlockNumber start, BlockNumber end,
 				bool *eof);
-static bool fsm_allow_writes(Relation rel, BlockNumber heapblk,
-				BlockNumber nblocks, BlockNumber *get_nblocks);
 
 
 /******** Public API ********/
@@ -150,46 +127,13 @@ static bool fsm_allow_writes(Relation rel, BlockNumber heapblk,
  * amount of free space available on that page and then try again (see
  * RecordAndGetPageWithFreeSpace).  If InvalidBlockNumber is returned,
  * extend the relation.
- *
- * For very small heap relations that don't have a FSM, we try every other
- * page before extending the relation.  To keep track of which pages have
- * been tried, initialize a local in-memory map of pages.
  */
 BlockNumber
-GetPageWithFreeSpace(Relation rel, Size spaceNeeded, bool check_fsm_only)
+GetPageWithFreeSpace(Relation rel, Size spaceNeeded)
 {
 	uint8		min_cat = fsm_space_needed_to_cat(spaceNeeded);
-	BlockNumber target_block,
-				nblocks;
-
-	/* First try the FSM, if it exists. */
-	target_block = fsm_search(rel, min_cat);
-
-	if (target_block == InvalidBlockNumber &&
-		(rel->rd_rel->relkind == RELKIND_RELATION ||
-		 rel->rd_rel->relkind == RELKIND_TOASTVALUE) &&
-		!check_fsm_only)
-	{
-		nblocks = RelationGetNumberOfBlocks(rel);
-
-		if (nblocks > HEAP_FSM_CREATION_THRESHOLD)
-		{
-			/*
-			 * If the FSM knows nothing of the rel, try the last page before
-			 * we give up and extend.  This avoids one-tuple-per-page syndrome
-			 * during bootstrapping or in a recently-started system.
-			 */
-			target_block = nblocks - 1;
-		}
-		else if (nblocks > 0)
-		{
-			/* Create or update local map and get first candidate block. */
-			fsm_local_set(rel, nblocks);
-			target_block = fsm_local_search();
-		}
-	}
 
-	return target_block;
+	return fsm_search(rel, min_cat);
 }
 
 /*
@@ -200,47 +144,16 @@ GetPageWithFreeSpace(Relation rel, Size spaceNeeded, bool check_fsm_only)
  * also some effort to return a page close to the old page; if there's a
  * page with enough free space on the same FSM page where the old one page
  * is located, it is preferred.
- *
- * For very small heap relations that don't have a FSM, we update the local
- * map to indicate we have tried a page, and return the next page to try.
  */
 BlockNumber
 RecordAndGetPageWithFreeSpace(Relation rel, BlockNumber oldPage,
 							  Size oldSpaceAvail, Size spaceNeeded)
 {
-	int			old_cat;
-	int			search_cat;
+	int			old_cat = fsm_space_avail_to_cat(oldSpaceAvail);
+	int			search_cat = fsm_space_needed_to_cat(spaceNeeded);
 	FSMAddress	addr;
 	uint16		slot;
 	int			search_slot;
-	BlockNumber nblocks = InvalidBlockNumber;
-
-	/* First try the local map, if it exists. */
-	if (FSM_LOCAL_MAP_EXISTS)
-	{
-		Assert((rel->rd_rel->relkind == RELKIND_RELATION ||
-				rel->rd_rel->relkind == RELKIND_TOASTVALUE) &&
-			   fsm_local_map.map[oldPage] == FSM_LOCAL_AVAIL);
-
-		fsm_local_map.map[oldPage] = FSM_LOCAL_NOT_AVAIL;
-		return fsm_local_search();
-	}
-
-	if (!fsm_allow_writes(rel, oldPage, InvalidBlockNumber, &nblocks))
-	{
-		/*
-		 * If we have neither a local map nor a FSM, we probably just
-		 * tried the target block in the smgr relation entry and failed,
-		 * so we'll need to create the local map.
-		 */
-		fsm_local_set(rel, nblocks);
-		return fsm_local_search();
-	}
-
-	/* Normal FSM logic follows */
-
-	old_cat = fsm_space_avail_to_cat(oldSpaceAvail);
-	search_cat = fsm_space_needed_to_cat(spaceNeeded);
 
 	/* Get the location of the FSM byte representing the heap block */
 	addr = fsm_get_location(oldPage, &slot);
@@ -263,41 +176,20 @@ RecordAndGetPageWithFreeSpace(Relation rel, BlockNumber oldPage,
  * Note that if the new spaceAvail value is higher than the old value stored
  * in the FSM, the space might not become visible to searchers until the next
  * FreeSpaceMapVacuum call, which updates the upper level pages.
- *
- * Callers have no need for a local map.
  */
 void
-RecordPageWithFreeSpace(Relation rel, BlockNumber heapBlk,
-						Size spaceAvail, BlockNumber nblocks)
+RecordPageWithFreeSpace(Relation rel, BlockNumber heapBlk, Size spaceAvail)
 {
-	int			new_cat;
+	int			new_cat = fsm_space_avail_to_cat(spaceAvail);
 	FSMAddress	addr;
 	uint16		slot;
-	BlockNumber dummy;
-
-	if (!fsm_allow_writes(rel, heapBlk, nblocks, &dummy))
-		/* No FSM to update and no local map either */
-		return;
 
 	/* Get the location of the FSM byte representing the heap block */
 	addr = fsm_get_location(heapBlk, &slot);
 
-	new_cat = fsm_space_avail_to_cat(spaceAvail);
 	fsm_set_and_search(rel, addr, slot, new_cat, 0);
 }
 
-/*
- * Clear the local map.  We must call this when we have found a block with
- * enough free space, when we extend the relation, or on transaction abort.
- */
-void
-FSMClearLocalMap(void)
-{
-	fsm_local_map.nblocks = 0;
-	memset(&fsm_local_map.map, FSM_LOCAL_NOT_AVAIL,
-		   sizeof(fsm_local_map.map));
-}
-
 /*
  * XLogRecordPageWithFreeSpace - like RecordPageWithFreeSpace, for use in
  *		WAL replay
@@ -312,30 +204,6 @@ XLogRecordPageWithFreeSpace(RelFileNode rnode, BlockNumber heapBlk,
 	BlockNumber blkno;
 	Buffer		buf;
 	Page		page;
-	bool		write_to_fsm;
-
-	/* This is meant to mirror the logic in fsm_allow_writes() */
-	if (heapBlk >= HEAP_FSM_CREATION_THRESHOLD)
-		write_to_fsm = true;
-	else
-	{
-		/* Open the relation at smgr level */
-		SMgrRelation smgr = smgropen(rnode, InvalidBackendId);
-
-		if (smgrexists(smgr, FSM_FORKNUM))
-			write_to_fsm = true;
-		else
-		{
-			BlockNumber heap_nblocks = smgrnblocks(smgr, MAIN_FORKNUM);
-			if (heap_nblocks > HEAP_FSM_CREATION_THRESHOLD)
-				write_to_fsm = true;
-			else
-				write_to_fsm = false;
-		}
-	}
-
-	if (!write_to_fsm)
-		return;
 
 	/* Get the location of the FSM byte representing the heap block */
 	addr = fsm_get_location(heapBlk, &slot);
@@ -1036,134 +904,3 @@ fsm_vacuum_page(Relation rel, FSMAddress addr,
 
 	return max_avail;
 }
-
-/*
- * For heaps, we prevent creation of the FSM unless the number of pages
- * exceeds HEAP_FSM_CREATION_THRESHOLD.  For tables that don't already have
- * a FSM, this will save an inode and a few kB of space.
- *
- * XXX The API is a little awkward -- if the caller passes a valid nblocks
- * value, it can avoid invoking a system call.  If the caller passes
- * InvalidBlockNumber and receives a false return value, it can get an
- * up-to-date relation size from get_nblocks.  This saves a few cycles in
- * the caller, which would otherwise need to get the relation size by itself.
- */
-static bool
-fsm_allow_writes(Relation rel, BlockNumber heapblk,
-				 BlockNumber nblocks, BlockNumber *get_nblocks)
-{
-	bool		skip_get_nblocks;
-
-	if (heapblk >= HEAP_FSM_CREATION_THRESHOLD)
-		return true;
-
-	/* Non-heap rels can always create a FSM. */
-	if (rel->rd_rel->relkind != RELKIND_RELATION &&
-		rel->rd_rel->relkind != RELKIND_TOASTVALUE)
-		return true;
-
-	/*
-	 * If the caller knows nblocks, we can avoid a system call later.
-	 * If it doesn't, maybe we have relpages from a previous VACUUM.
-	 * Since the table may have extended since then, we still have to
-	 * count the pages later if we can't return now.
-	 */
-	if (nblocks != InvalidBlockNumber)
-	{
-		if (nblocks > HEAP_FSM_CREATION_THRESHOLD)
-			return true;
-		else
-			skip_get_nblocks = true;
-	}
-	else
-	{
-		if (rel->rd_rel->relpages != InvalidBlockNumber &&
-			rel->rd_rel->relpages > HEAP_FSM_CREATION_THRESHOLD)
-			return true;
-		else
-			skip_get_nblocks = false;
-	}
-
-	RelationOpenSmgr(rel);
-	if (smgrexists(rel->rd_smgr, FSM_FORKNUM))
-		return true;
-
-	if (skip_get_nblocks)
-		return false;
-
-	/* last resort */
-	*get_nblocks = RelationGetNumberOfBlocks(rel);
-	if (*get_nblocks > HEAP_FSM_CREATION_THRESHOLD)
-		return true;
-	else
-		return false;
-}
-
-/*
- * Initialize or update the local map of blocks to try, for when there is
- * no FSM.
- *
- * When we initialize the map, the whole heap is potentially available to
- * try.  Testing revealed that trying every block can cause a small
- * performance dip compared to when we use a FSM, so we try every other
- * block instead.
- */
-static void
-fsm_local_set(Relation rel, BlockNumber cur_nblocks)
-{
-	BlockNumber blkno,
-				cached_target_block;
-
-	/* The local map must not be set already. */
-	Assert(!FSM_LOCAL_MAP_EXISTS);
-
-	/*
-	 * Starting at the current last block in the relation and working
-	 * backwards, mark alternating blocks as available.
-	 */
-	blkno = cur_nblocks - 1;
-	while (true)
-	{
-		fsm_local_map.map[blkno] = FSM_LOCAL_AVAIL;
-		if (blkno >= 2)
-			blkno -= 2;
-		else
-			break;
-	}
-
-	/* Cache the number of blocks. */
-	fsm_local_map.nblocks = cur_nblocks;
-
-	/* Set the status of the cached target block to 'unavailable'. */
-	cached_target_block = RelationGetTargetBlock(rel);
-	if (cached_target_block != InvalidBlockNumber &&
-		cached_target_block < cur_nblocks)
-		fsm_local_map.map[cached_target_block] = FSM_LOCAL_NOT_AVAIL;
-}
-
-/*
- * Search the local map for an available block to try, in descending order.
- * As such, there is no heuristic available to decide which order will be
- * better to try, but the probability of having space in the last block in the
- * map is higher because that is the most recent block added to the heap.
- *
- * This function is used when there is no FSM.
- */
-static BlockNumber
-fsm_local_search(void)
-{
-	BlockNumber		target_block;
-
-	/* Local map must be set by now. */
-	Assert(FSM_LOCAL_MAP_EXISTS);
-
-	target_block = fsm_local_map.nblocks;
-	do
-	{
-		target_block--;
-		if (fsm_local_map.map[target_block] == FSM_LOCAL_AVAIL)
-			return target_block;
-	} while (target_block > 0);
-
-	return InvalidBlockNumber;
-}

src/backend/storage/freespace/indexfsm.c

@@ -37,7 +37,7 @@
 BlockNumber
 GetFreeIndexPage(Relation rel)
 {
-	BlockNumber blkno = GetPageWithFreeSpace(rel, BLCKSZ / 2, true);
+	BlockNumber blkno = GetPageWithFreeSpace(rel, BLCKSZ / 2);
 
 	if (blkno != InvalidBlockNumber)
 		RecordUsedIndexPage(rel, blkno);
@@ -51,7 +51,7 @@ GetFreeIndexPage(Relation rel)
 void
 RecordFreeIndexPage(Relation rel, BlockNumber freeBlock)
 {
-	RecordPageWithFreeSpace(rel, freeBlock, BLCKSZ - 1, InvalidBlockNumber);
+	RecordPageWithFreeSpace(rel, freeBlock, BLCKSZ - 1);
 }
 
 
@@ -61,7 +61,7 @@ RecordFreeIndexPage(Relation rel, BlockNumber freeBlock)
 void
 RecordUsedIndexPage(Relation rel, BlockNumber usedBlock)
 {
-	RecordPageWithFreeSpace(rel, usedBlock, 0, InvalidBlockNumber);
+	RecordPageWithFreeSpace(rel, usedBlock, 0);
 }
 
 /*

src/include/storage/freespace.h

@@ -18,20 +18,15 @@
 #include "storage/relfilenode.h"
 #include "utils/relcache.h"
 
-/* Only create the FSM if the heap has greater than this many blocks */
-#define HEAP_FSM_CREATION_THRESHOLD 4
-
 /* prototypes for public functions in freespace.c */
 extern Size GetRecordedFreeSpace(Relation rel, BlockNumber heapBlk);
-extern BlockNumber GetPageWithFreeSpace(Relation rel, Size spaceNeeded,
-					 bool check_fsm_only);
+extern BlockNumber GetPageWithFreeSpace(Relation rel, Size spaceNeeded);
 extern BlockNumber RecordAndGetPageWithFreeSpace(Relation rel,
 							  BlockNumber oldPage,
 							  Size oldSpaceAvail,
 							  Size spaceNeeded);
 extern void RecordPageWithFreeSpace(Relation rel, BlockNumber heapBlk,
-						Size spaceAvail, BlockNumber nblocks);
-extern void FSMClearLocalMap(void);
+						Size spaceAvail);
 extern void XLogRecordPageWithFreeSpace(RelFileNode rnode, BlockNumber heapBlk,
 							Size spaceAvail);
 

src/test/regress/expected/fsm.out

---
--- Free Space Map test
---
-CREATE TABLE fsm_check_size (num int, str text);
--- Fill 3 blocks with as many large records as will fit
--- No FSM
-INSERT INTO fsm_check_size SELECT i, rpad('', 1024, 'a')
-FROM generate_series(1,7*3) i;
-VACUUM fsm_check_size;
-SELECT pg_relation_size('fsm_check_size', 'main') AS heap_size,
-pg_relation_size('fsm_check_size', 'fsm') AS fsm_size;
- heap_size | fsm_size 
------------+----------
-     24576 |        0
-(1 row)
-
--- Clear some space on block 0
-DELETE FROM fsm_check_size WHERE num <= 5;
-VACUUM fsm_check_size;
--- Insert small record in block 2 to set the cached smgr targetBlock
-INSERT INTO fsm_check_size VALUES(99, 'b');
--- Insert large record and make sure it goes in block 0 rather than
--- causing the relation to extend
-INSERT INTO fsm_check_size VALUES (101, rpad('', 1024, 'a'));
-SELECT pg_relation_size('fsm_check_size', 'main') AS heap_size,
-pg_relation_size('fsm_check_size', 'fsm') AS fsm_size;
- heap_size | fsm_size 
------------+----------
-     24576 |        0
-(1 row)
-
--- Extend table with enough blocks to exceed the FSM threshold
--- FSM is created and extended to 3 blocks
-INSERT INTO fsm_check_size SELECT i, 'c' FROM generate_series(200,1200) i;
-VACUUM fsm_check_size;
-SELECT pg_relation_size('fsm_check_size', 'fsm') AS fsm_size;
- fsm_size 
-----------
-    24576
-(1 row)
-
--- Truncate heap to 1 block
--- No change in FSM
-DELETE FROM fsm_check_size WHERE num > 7;
-VACUUM fsm_check_size;
-SELECT pg_relation_size('fsm_check_size', 'fsm') AS fsm_size;
- fsm_size 
-----------
-    24576
-(1 row)
-
--- Truncate heap to 0 blocks
--- FSM now truncated to 2 blocks
-DELETE FROM fsm_check_size;
-VACUUM fsm_check_size;
-SELECT pg_relation_size('fsm_check_size', 'fsm') AS fsm_size;
- fsm_size 
-----------
-    16384
-(1 row)
-
--- Add long random string to extend TOAST table to 1 block
-INSERT INTO fsm_check_size
-VALUES(0, (SELECT string_agg(md5(chr(i)), '')
-		   FROM generate_series(1,100) i));
-VACUUM fsm_check_size;
-SELECT pg_relation_size(reltoastrelid, 'main') AS toast_size,
-pg_relation_size(reltoastrelid, 'fsm') AS toast_fsm_size
-FROM pg_class WHERE relname = 'fsm_check_size';
- toast_size | toast_fsm_size 
-------------+----------------
-       8192 |              0
-(1 row)
-
-DROP TABLE fsm_check_size;

src/test/regress/parallel_schedule

@@ -68,12 +68,6 @@ test: create_aggregate create_function_3 create_cast constraints triggers inheri
 # ----------
 test: sanity_check
 
-# ----------
-# fsm does a delete followed by vacuum, and running it in parallel can prevent
-# removal of rows.
-# ----------
-test: fsm
-
 # ----------
 # Believe it or not, select creates a table, subsequent
 # tests need.

src/test/regress/serial_schedule

@@ -80,7 +80,6 @@ test: roleattributes
 test: create_am
 test: hash_func
 test: sanity_check
-test: fsm
 test: errors
 test: select
 test: select_into

src/test/regress/sql/fsm.sql

---
--- Free Space Map test
---
-
-CREATE TABLE fsm_check_size (num int, str text);
-
--- Fill 3 blocks with as many large records as will fit
--- No FSM
-INSERT INTO fsm_check_size SELECT i, rpad('', 1024, 'a')
-FROM generate_series(1,7*3) i;
-VACUUM fsm_check_size;
-SELECT pg_relation_size('fsm_check_size', 'main') AS heap_size,
-pg_relation_size('fsm_check_size', 'fsm') AS fsm_size;
-
--- Clear some space on block 0
-DELETE FROM fsm_check_size WHERE num <= 5;
-VACUUM fsm_check_size;
-
--- Insert small record in block 2 to set the cached smgr targetBlock
-INSERT INTO fsm_check_size VALUES(99, 'b');
-
--- Insert large record and make sure it goes in block 0 rather than
--- causing the relation to extend
-INSERT INTO fsm_check_size VALUES (101, rpad('', 1024, 'a'));
-SELECT pg_relation_size('fsm_check_size', 'main') AS heap_size,
-pg_relation_size('fsm_check_size', 'fsm') AS fsm_size;
-
--- Extend table with enough blocks to exceed the FSM threshold
--- FSM is created and extended to 3 blocks
-INSERT INTO fsm_check_size SELECT i, 'c' FROM generate_series(200,1200) i;
-VACUUM fsm_check_size;
-SELECT pg_relation_size('fsm_check_size', 'fsm') AS fsm_size;
-
--- Truncate heap to 1 block
--- No change in FSM
-DELETE FROM fsm_check_size WHERE num > 7;
-VACUUM fsm_check_size;
-SELECT pg_relation_size('fsm_check_size', 'fsm') AS fsm_size;
-
--- Truncate heap to 0 blocks
--- FSM now truncated to 2 blocks
-DELETE FROM fsm_check_size;
-VACUUM fsm_check_size;
-SELECT pg_relation_size('fsm_check_size', 'fsm') AS fsm_size;
-
--- Add long random string to extend TOAST table to 1 block
-INSERT INTO fsm_check_size
-VALUES(0, (SELECT string_agg(md5(chr(i)), '')
-		   FROM generate_series(1,100) i));
-VACUUM fsm_check_size;
-SELECT pg_relation_size(reltoastrelid, 'main') AS toast_size,
-pg_relation_size(reltoastrelid, 'fsm') AS toast_fsm_size
-FROM pg_class WHERE relname = 'fsm_check_size';
-
-DROP TABLE fsm_check_size;