Modify hash_search() API to prevent future occurrences of the error

spotted by Qingqing Zhou.  The HASH_ENTER action now automatically
fails with elog(ERROR) on out-of-memory --- which incidentally lets
us eliminate duplicate error checks in quite a bunch of places.  If
you really need the old return-NULL-on-out-of-memory behavior, you
can ask for HASH_ENTER_NULL.  But there is now an Assert in that path
checking that you aren't hoping to get that behavior in a palloc-based
hash table.
Along the way, remove the old HASH_FIND_SAVE/HASH_REMOVE_SAVED actions,
which were not being used anywhere anymore, and were surely too ugly
and unsafe to want to see revived again.

contrib/dblink/dblink.c

@@ -2061,11 +2061,6 @@ createNewConnection(const char *name, remoteConn * con)
 	hentry = (remoteConnHashEnt *) hash_search(remoteConnHash, key,
 											   HASH_ENTER, &found);
 
-	if (!hentry)
-		ereport(ERROR,
-				(errcode(ERRCODE_OUT_OF_MEMORY),
-				 errmsg("out of memory")));
-
 	if (found)
 		ereport(ERROR,
 				(errcode(ERRCODE_DUPLICATE_OBJECT),

contrib/tablefunc/tablefunc.c

@@ -144,10 +144,6 @@ do { \
 	snprintf(key, MAX_CATNAME_LEN - 1, "%s", CATDESC->catname); \
 	hentry = (crosstab_HashEnt*) hash_search(crosstab_HashTable, \
 										 key, HASH_ENTER, &found); \
-	if (hentry == NULL) \
-		ereport(ERROR, \
-				(errcode(ERRCODE_OUT_OF_MEMORY), \
-				 errmsg("out of memory"))); \
 	if (found) \
 		ereport(ERROR, \
 				(errcode(ERRCODE_DUPLICATE_OBJECT), \

src/backend/access/transam/xlogutils.c

@@ -11,7 +11,7 @@
  * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/backend/access/transam/xlogutils.c,v 1.36 2005/01/10 20:02:19 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/access/transam/xlogutils.c,v 1.37 2005/05/29 04:23:03 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -223,9 +223,6 @@ XLogOpenRelation(bool redo, RmgrId rmid, RelFileNode rnode)
 		hentry = (XLogRelCacheEntry *)
 			hash_search(_xlrelcache, (void *) &rnode, HASH_ENTER, &found);
 
-		if (hentry == NULL)
-			elog(PANIC, "XLogOpenRelation: out of memory for cache");
-
 		if (found)
 			elog(PANIC, "XLogOpenRelation: file found on insert into cache");
 

src/backend/commands/prepare.c

@@ -10,7 +10,7 @@
  * Copyright (c) 2002-2005, PostgreSQL Global Development Group
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/commands/prepare.c,v 1.37 2005/05/24 04:18:04 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/commands/prepare.c,v 1.38 2005/05/29 04:23:03 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -346,9 +346,9 @@ StorePreparedStatement(const char *stmt_name,
 											  HASH_ENTER,
 											  &found);
 
-	/* Shouldn't get a failure, nor a duplicate entry */
-	if (!entry || found)
-		elog(ERROR, "could not store prepared statement \"%s\"",
+	/* Shouldn't get a duplicate entry */
+	if (found)
+		elog(ERROR, "duplicate prepared statement \"%s\"",
 			 stmt_name);
 
 	/* Fill in the hash table entry with copied data */

src/backend/executor/execGrouping.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/executor/execGrouping.c,v 1.14 2005/03/16 21:38:06 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/executor/execGrouping.c,v 1.15 2005/05/29 04:23:03 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -379,13 +379,9 @@ LookupTupleHashEntry(TupleHashTable hashtable, TupleTableSlot *slot,
 		}
 		else
 		{
-			/* created new entry ... we hope */
-			if (entry == NULL)
-				ereport(ERROR,
-						(errcode(ERRCODE_OUT_OF_MEMORY),
-						 errmsg("out of memory")));
-
 			/*
+			 * created new entry
+			 *
 			 * Zero any caller-requested space in the entry.  (This zaps
 			 * the "key data" dynahash.c copied into the new entry, but we
 			 * don't care since we're about to overwrite it anyway.)

src/backend/nodes/tidbitmap.c

@@ -23,7 +23,7 @@
  * Copyright (c) 2003-2005, PostgreSQL Global Development Group
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/nodes/tidbitmap.c,v 1.3 2005/05/17 00:43:47 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/nodes/tidbitmap.c,v 1.4 2005/05/29 04:23:03 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -220,10 +220,6 @@ tbm_create_pagetable(TIDBitmap *tbm)
 		page = (PagetableEntry *) hash_search(tbm->pagetable,
 											  (void *) &tbm->entry1.blockno,
 											  HASH_ENTER, &found);
-		if (page == NULL)
-			ereport(ERROR,
-					(errcode(ERRCODE_OUT_OF_MEMORY),
-					 errmsg("out of memory")));
 		Assert(!found);
 		memcpy(page, &tbm->entry1, sizeof(PagetableEntry));
 	}
@@ -726,10 +722,6 @@ tbm_get_pageentry(TIDBitmap *tbm, BlockNumber pageno)
 		page = (PagetableEntry *) hash_search(tbm->pagetable,
 											  (void *) &pageno,
 											  HASH_ENTER, &found);
-		if (page == NULL)
-			ereport(ERROR,
-					(errcode(ERRCODE_OUT_OF_MEMORY),
-					 errmsg("out of memory")));
 	}
 
 	/* Initialize it if not present before */
@@ -820,10 +812,6 @@ tbm_mark_page_lossy(TIDBitmap *tbm, BlockNumber pageno)
 	page = (PagetableEntry *) hash_search(tbm->pagetable,
 										  (void *) &chunk_pageno,
 										  HASH_ENTER, &found);
-	if (page == NULL)
-		ereport(ERROR,
-				(errcode(ERRCODE_OUT_OF_MEMORY),
-				 errmsg("out of memory")));
 
 	/* Initialize it if not present before */
 	if (!found)

src/backend/postmaster/pgstat.c

@@ -13,7 +13,7 @@
  *
  *	Copyright (c) 2001-2005, PostgreSQL Global Development Group
  *
- *	$PostgreSQL: pgsql/src/backend/postmaster/pgstat.c,v 1.94 2005/05/11 01:41:40 neilc Exp $
+ *	$PostgreSQL: pgsql/src/backend/postmaster/pgstat.c,v 1.95 2005/05/29 04:23:03 tgl Exp $
  * ----------
  */
 #include "postgres.h"
@@ -2061,10 +2061,6 @@ pgstat_get_db_entry(int databaseid)
 	result = (PgStat_StatDBEntry *) hash_search(pgStatDBHash,
 												&databaseid,
 												HASH_ENTER, &found);
-	if (result == NULL)
-		ereport(ERROR,
-				(errcode(ERRCODE_OUT_OF_MEMORY),
-				 errmsg("out of memory in statistics collector --- abort")));
 
 	/* If not found, initialize the new one. */
 	if (!found)
@@ -2126,10 +2122,6 @@ pgstat_sub_backend(int procpid)
 													   (void *) &procpid,
 													   HASH_ENTER,
 													   &found);
-			if (deadbe == NULL)
-				ereport(ERROR,
-						(errcode(ERRCODE_OUT_OF_MEMORY),
-						 errmsg("out of memory in statistics collector --- abort")));
 
 			if (!found)
 			{
@@ -2435,12 +2427,6 @@ pgstat_read_statsfile(HTAB **dbhash, Oid onlydb,
 											  (void *) &dbbuf.databaseid,
 															 HASH_ENTER,
 															 &found);
-				if (dbentry == NULL)
-				{
-					ereport(ERROR,
-							(errcode(ERRCODE_OUT_OF_MEMORY),
-							 errmsg("out of memory")));
-				}
 				if (found)
 				{
 					ereport(pgStatRunningInCollector ? LOG : WARNING,
@@ -2503,10 +2489,6 @@ pgstat_read_statsfile(HTAB **dbhash, Oid onlydb,
 				tabentry = (PgStat_StatTabEntry *) hash_search(tabhash,
 												(void *) &tabbuf.tableid,
 													 HASH_ENTER, &found);
-				if (tabentry == NULL)
-					ereport(ERROR,
-							(errcode(ERRCODE_OUT_OF_MEMORY),
-							 errmsg("out of memory")));
 
 				if (found)
 				{
@@ -2730,10 +2712,6 @@ pgstat_recv_tabstat(PgStat_MsgTabstat *msg, int len)
 		tabentry = (PgStat_StatTabEntry *) hash_search(dbentry->tables,
 											  (void *) &(tabmsg[i].t_id),
 													 HASH_ENTER, &found);
-		if (tabentry == NULL)
-			ereport(ERROR,
-					(errcode(ERRCODE_OUT_OF_MEMORY),
-			 errmsg("out of memory in statistics collector --- abort")));
 
 		if (!found)
 		{

src/backend/storage/buffer/buf_table.c

@@ -13,7 +13,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/storage/buffer/buf_table.c,v 1.40 2005/03/04 20:21:06 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/storage/buffer/buf_table.c,v 1.41 2005/05/29 04:23:04 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -110,11 +110,6 @@ BufTableInsert(BufferTag *tagPtr, int buf_id)
 	result = (BufferLookupEnt *)
 		hash_search(SharedBufHash, (void *) tagPtr, HASH_ENTER, &found);
 
-	if (!result)
-		ereport(ERROR,
-				(errcode(ERRCODE_OUT_OF_MEMORY),
-				 errmsg("out of shared memory")));
-
 	if (found)					/* found something already in the table */
 		return result->id;
 

src/backend/storage/buffer/localbuf.c

@@ -9,7 +9,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/storage/buffer/localbuf.c,v 1.66 2005/03/19 23:27:05 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/storage/buffer/localbuf.c,v 1.67 2005/05/29 04:23:04 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -192,10 +192,6 @@ LocalBufferAlloc(Relation reln, BlockNumber blockNum, bool *foundPtr)
 
 	hresult = (LocalBufferLookupEnt *)
 		hash_search(LocalBufHash, (void *) &newTag, HASH_ENTER, &found);
-	if (!hresult)
-		ereport(ERROR,
-				(errcode(ERRCODE_OUT_OF_MEMORY),
-				 errmsg("out of memory")));
 	if (found)				/* shouldn't happen */
 		elog(ERROR, "local buffer hash table corrupted");
 	hresult->id = 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 1.44 2005/04/24 03:51:49 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/storage/freespace/freespace.c,v 1.45 2005/05/29 04:23:04 tgl Exp $
  *
  *
  * NOTES:
@@ -1036,10 +1036,6 @@ create_fsm_rel(RelFileNode *rel)
 										 (void *) rel,
 										 HASH_ENTER,
 										 &found);
-	if (!fsmrel)
-		ereport(ERROR,
-				(errcode(ERRCODE_OUT_OF_MEMORY),
-				 errmsg("out of shared memory")));
 
 	if (!found)
 	{

src/backend/storage/ipc/shmem.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/storage/ipc/shmem.c,v 1.83 2005/04/04 04:34:41 neilc Exp $
+ *	  $PostgreSQL: pgsql/src/backend/storage/ipc/shmem.c,v 1.84 2005/05/29 04:23:04 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -235,10 +235,6 @@ InitShmemIndex(void)
 
 		result = (ShmemIndexEnt *)
 			hash_search(ShmemIndex, (void *) &item, HASH_ENTER, &found);
-		if (!result)
-			ereport(FATAL,
-					(errcode(ERRCODE_OUT_OF_MEMORY),
-					 errmsg("out of shared memory")));
 
 		Assert(!found);
 
@@ -367,7 +363,7 @@ ShmemInitStruct(const char *name, Size size, bool *foundPtr)
 
 	/* look it up in the shmem index */
 	result = (ShmemIndexEnt *)
-		hash_search(ShmemIndex, (void *) &item, HASH_ENTER, foundPtr);
+		hash_search(ShmemIndex, (void *) &item, HASH_ENTER_NULL, foundPtr);
 
 	if (!result)
 	{
@@ -375,7 +371,6 @@ ShmemInitStruct(const char *name, Size size, bool *foundPtr)
 		ereport(ERROR,
 				(errcode(ERRCODE_OUT_OF_MEMORY),
 				 errmsg("out of shared memory")));
-		return NULL;
 	}
 
 	if (*foundPtr)

src/backend/storage/lmgr/lock.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/storage/lmgr/lock.c,v 1.152 2005/05/19 23:30:18 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/storage/lmgr/lock.c,v 1.153 2005/05/29 04:23:04 tgl Exp $
  *
  * NOTES
  *	  Outside modules can create a lock table and acquire/release
@@ -470,10 +470,6 @@ LockAcquire(LOCKMETHODID lockmethodid, LOCKTAG *locktag,
 	locallock = (LOCALLOCK *) hash_search(LockMethodLocalHash[lockmethodid],
 										  (void *) &localtag,
 										  HASH_ENTER, &found);
-	if (!locallock)
-		ereport(ERROR,
-				(errcode(ERRCODE_OUT_OF_MEMORY),
-				 errmsg("out of memory")));
 
 	/*
 	 * if it's a new locallock object, initialize it
@@ -531,7 +527,7 @@ LockAcquire(LOCKMETHODID lockmethodid, LOCKTAG *locktag,
 	 */
 	lock = (LOCK *) hash_search(LockMethodLockHash[lockmethodid],
 								(void *) locktag,
-								HASH_ENTER, &found);
+								HASH_ENTER_NULL, &found);
 	if (!lock)
 	{
 		LWLockRelease(masterLock);
@@ -578,7 +574,7 @@ LockAcquire(LOCKMETHODID lockmethodid, LOCKTAG *locktag,
 	 */
 	proclock = (PROCLOCK *) hash_search(LockMethodProcLockHash[lockmethodid],
 										(void *) &proclocktag,
-										HASH_ENTER, &found);
+										HASH_ENTER_NULL, &found);
 	if (!proclock)
 	{
 		/* Ooops, not enough shmem for the proclock */

src/backend/storage/smgr/md.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/storage/smgr/md.c,v 1.114 2004/12/31 22:01:13 pgsql Exp $
+ *	  $PostgreSQL: pgsql/src/backend/storage/smgr/md.c,v 1.115 2005/05/29 04:23:05 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -805,9 +805,8 @@ register_dirty_segment(SMgrRelation reln, MdfdVec *seg)
 		entry.rnode = reln->smgr_rnode;
 		entry.segno = seg->mdfd_segno;
 
-		if (hash_search(pendingOpsTable, &entry, HASH_ENTER, NULL) != NULL)
+		(void) hash_search(pendingOpsTable, &entry, HASH_ENTER, NULL);
 		return true;
-		/* out of memory: fall through to do it locally */
 	}
 	else
 	{
@@ -838,10 +837,7 @@ RememberFsyncRequest(RelFileNode rnode, BlockNumber segno)
 	entry.rnode = rnode;
 	entry.segno = segno;
 
-	if (hash_search(pendingOpsTable, &entry, HASH_ENTER, NULL) == NULL)
-		ereport(FATAL,
-				(errcode(ERRCODE_OUT_OF_MEMORY),
-				 errmsg("out of memory")));
+	(void) hash_search(pendingOpsTable, &entry, HASH_ENTER, NULL);
 }
 
 /*

src/backend/storage/smgr/smgr.c

@@ -11,7 +11,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/storage/smgr/smgr.c,v 1.86 2005/03/20 22:00:53 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/storage/smgr/smgr.c,v 1.87 2005/05/29 04:23:05 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -207,10 +207,6 @@ smgropen(RelFileNode rnode)
 	reln = (SMgrRelation) hash_search(SMgrRelationHash,
 									  (void *) &rnode,
 									  HASH_ENTER, &found);
-	if (reln == NULL)
-		ereport(ERROR,
-				(errcode(ERRCODE_OUT_OF_MEMORY),
-				 errmsg("out of memory")));
 
 	/* Initialize it if not present before */
 	if (!found)

src/backend/utils/adt/ri_triggers.c

@@ -17,7 +17,7 @@
  *
  * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
  *
- * $PostgreSQL: pgsql/src/backend/utils/adt/ri_triggers.c,v 1.77 2005/04/28 21:47:15 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/utils/adt/ri_triggers.c,v 1.78 2005/05/29 04:23:05 tgl Exp $
  *
  * ----------
  */
@@ -3466,10 +3466,6 @@ ri_HashPreparedPlan(RI_QueryKey *key, void *plan)
 	entry = (RI_QueryHashEntry *) hash_search(ri_query_cache,
 											  (void *) key,
 											  HASH_ENTER, &found);
-	if (entry == NULL)
-		ereport(ERROR,
-				(errcode(ERRCODE_OUT_OF_MEMORY),
-				 errmsg("out of memory")));
 	entry->plan = plan;
 }
 

src/backend/utils/cache/relcache.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/cache/relcache.c,v 1.224 2005/05/27 23:31:20 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/cache/relcache.c,v 1.225 2005/05/29 04:23:05 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -137,10 +137,6 @@ do { \
 										   (void *) &(RELATION->rd_id), \
 										   HASH_ENTER, \
 										   &found); \
-	if (idhentry == NULL) \
-		ereport(ERROR, \
-				(errcode(ERRCODE_OUT_OF_MEMORY), \
-				 errmsg("out of memory"))); \
 	/* used to give notice if found -- now just keep quiet */ \
 	idhentry->reldesc = RELATION; \
 } while(0)
@@ -1044,10 +1040,6 @@ LookupOpclassInfo(Oid operatorClassOid,
 	opcentry = (OpClassCacheEnt *) hash_search(OpClassCache,
 											   (void *) &operatorClassOid,
 											   HASH_ENTER, &found);
-	if (opcentry == NULL)
-		ereport(ERROR,
-				(errcode(ERRCODE_OUT_OF_MEMORY),
-				 errmsg("out of memory")));
 
 	if (found && opcentry->valid)
 	{

src/backend/utils/cache/typcache.c

@@ -36,7 +36,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/cache/typcache.c,v 1.13 2005/04/14 20:32:43 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/cache/typcache.c,v 1.14 2005/05/29 04:23:06 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -158,10 +158,6 @@ lookup_type_cache(Oid type_id, int flags)
 		typentry = (TypeCacheEntry *) hash_search(TypeCacheHash,
 												  (void *) &type_id,
 												  HASH_ENTER, &found);
-		if (typentry == NULL)
-			ereport(ERROR,
-					(errcode(ERRCODE_OUT_OF_MEMORY),
-					 errmsg("out of memory")));
 		Assert(!found);			/* it wasn't there a moment ago */
 
 		MemSet(typentry, 0, sizeof(TypeCacheEntry));
@@ -480,10 +476,6 @@ assign_record_type_typmod(TupleDesc tupDesc)
 	recentry = (RecordCacheEntry *) hash_search(RecordCacheHash,
 												(void *) hashkey,
 												HASH_ENTER, &found);
-	if (recentry == NULL)
-		ereport(ERROR,
-				(errcode(ERRCODE_OUT_OF_MEMORY),
-				 errmsg("out of memory")));
 	if (!found)
 	{
 		/* New entry ... hash_search initialized only the hash key */

src/backend/utils/fmgr/fmgr.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/fmgr/fmgr.c,v 1.94 2005/04/14 20:32:43 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/fmgr/fmgr.c,v 1.95 2005/05/29 04:23:06 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -521,10 +521,6 @@ record_C_func(HeapTuple procedureTuple,
 					&fn_oid,
 					HASH_ENTER,
 					&found);
-	if (entry == NULL)
-		ereport(ERROR,
-				(errcode(ERRCODE_OUT_OF_MEMORY),
-				 errmsg("out of memory")));
 	/* OID is already filled in */
 	entry->fn_xmin = HeapTupleHeaderGetXmin(procedureTuple->t_data);
 	entry->fn_cmin = HeapTupleHeaderGetCmin(procedureTuple->t_data);

src/backend/utils/hash/dynahash.c

@@ -9,7 +9,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/hash/dynahash.c,v 1.60 2005/05/16 00:19:04 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/hash/dynahash.c,v 1.61 2005/05/29 04:23:06 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -498,22 +498,22 @@ calc_bucket(HASHHDR *hctl, uint32 hash_val)
  * action is one of:
  *		HASH_FIND: look up key in table
  *		HASH_ENTER: look up key in table, creating entry if not present
+ *		HASH_ENTER_NULL: same, but return NULL if out of memory
  *		HASH_REMOVE: look up key in table, remove entry if present
- *		HASH_FIND_SAVE: look up key in table, also save in static var
- *		HASH_REMOVE_SAVED: remove entry saved by HASH_FIND_SAVE
  *
  * Return value is a pointer to the element found/entered/removed if any,
- * or NULL if no match was found.  (NB: in the case of the REMOVE actions,
+ * or NULL if no match was found.  (NB: in the case of the REMOVE action,
  * the result is a dangling pointer that shouldn't be dereferenced!)
- * A NULL result for HASH_ENTER implies we ran out of memory.
+ *
+ * HASH_ENTER will normally ereport a generic "out of memory" error if
+ * it is unable to create a new entry.  The HASH_ENTER_NULL operation is
+ * the same except it will return NULL if out of memory.  Note that
+ * HASH_ENTER_NULL cannot be used with the default palloc-based allocator,
+ * since palloc internally ereports on out-of-memory.
  *
  * If foundPtr isn't NULL, then *foundPtr is set TRUE if we found an
  * existing entry in the table, FALSE otherwise.  This is needed in the
  * HASH_ENTER case, but is redundant with the return value otherwise.
- *
- * The HASH_FIND_SAVE/HASH_REMOVE_SAVED interface is a hack to save one
- * table lookup in a find/process/remove scenario.	Note that no other
- * addition or removal in the table can safely happen in between.
  *----------
  */
 void *
@@ -523,19 +523,15 @@ hash_search(HTAB *hashp,
 			bool *foundPtr)
 {
 	HASHHDR    *hctl = hashp->hctl;
-	uint32		hashvalue = 0;
+	Size		keysize = hctl->keysize;
+	uint32		hashvalue;
 	uint32		bucket;
 	long		segment_num;
 	long		segment_ndx;
 	HASHSEGMENT segp;
 	HASHBUCKET	currBucket;
 	HASHBUCKET *prevBucketPtr;
-
-	static struct State
-	{
-		HASHBUCKET	currBucket;
-		HASHBUCKET *prevBucketPtr;
-	}			saveState;
+	HashCompareFunc match;
 
 #if HASH_STATISTICS
 	hash_accesses++;
@@ -543,24 +539,8 @@ hash_search(HTAB *hashp,
 #endif
 
 	/*
-	 * Do the initial lookup (or recall result of prior lookup)
+	 * Do the initial lookup
 	 */
-	if (action == HASH_REMOVE_SAVED)
-	{
-		currBucket = saveState.currBucket;
-		prevBucketPtr = saveState.prevBucketPtr;
-
-		/*
-		 * Try to catch subsequent errors
-		 */
-		Assert(currBucket);
-		saveState.currBucket = NULL;
-	}
-	else
-	{
-		HashCompareFunc match;
-		Size		keysize = hctl->keysize;
-
 	hashvalue = hashp->hash(keyPtr, keysize);
 	bucket = calc_bucket(hctl, hashvalue);
 
@@ -579,6 +559,7 @@ hash_search(HTAB *hashp,
 	 * Follow collision chain looking for matching key
 	 */
 	match = hashp->match;		/* save one fetch in inner loop */
+
 	while (currBucket != NULL)
 	{
 		if (currBucket->hashvalue == hashvalue &&
@@ -591,7 +572,6 @@ hash_search(HTAB *hashp,
 		hctl->collisions++;
 #endif
 	}
-	}
 
 	if (foundPtr)
 		*foundPtr = (bool) (currBucket != NULL);
@@ -606,17 +586,7 @@ hash_search(HTAB *hashp,
 				return (void *) ELEMENTKEY(currBucket);
 			return NULL;
 
-		case HASH_FIND_SAVE:
-			if (currBucket != NULL)
-			{
-				saveState.currBucket = currBucket;
-				saveState.prevBucketPtr = prevBucketPtr;
-				return (void *) ELEMENTKEY(currBucket);
-			}
-			return NULL;
-
 		case HASH_REMOVE:
-		case HASH_REMOVE_SAVED:
 			if (currBucket != NULL)
 			{
 				Assert(hctl->nentries > 0);
@@ -638,6 +608,11 @@ hash_search(HTAB *hashp,
 			}
 			return NULL;
 
+		case HASH_ENTER_NULL:
+			/* ENTER_NULL does not work with palloc-based allocator */
+			Assert(hashp->alloc != DynaHashAlloc);
+			/* FALL THRU */
+
 		case HASH_ENTER:
 			/* Return existing element if found, else create one */
 			if (currBucket != NULL)
@@ -649,7 +624,20 @@ hash_search(HTAB *hashp,
 			{
 				/* no free elements.  allocate another chunk of buckets */
 				if (!element_alloc(hashp, HASHELEMENT_ALLOC_INCR))
-					return NULL;	/* out of memory */
+				{
+					/* out of memory */
+					if (action == HASH_ENTER_NULL)
+						return NULL;
+					/* report a generic message */
+					if (hashp->isshared)
+						ereport(ERROR,
+								(errcode(ERRCODE_OUT_OF_MEMORY),
+								 errmsg("out of shared memory")));
+					else
+						ereport(ERROR,
+								(errcode(ERRCODE_OUT_OF_MEMORY),
+								 errmsg("out of memory")));
+				}
 				currBucket = hctl->freeList;
 				Assert(currBucket != NULL);
 			}

src/backend/utils/mmgr/portalmem.c

@@ -12,7 +12,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/mmgr/portalmem.c,v 1.79 2005/05/11 18:05:37 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/mmgr/portalmem.c,v 1.80 2005/05/29 04:23:06 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -72,10 +72,6 @@ do { \
 	StrNCpy(key, NAME, MAX_PORTALNAME_LEN); \
 	hentry = (PortalHashEnt*)hash_search(PortalHashTable, \
 										 key, HASH_ENTER, &found); \
-	if (hentry == NULL) \
-		ereport(ERROR, \
-				(errcode(ERRCODE_OUT_OF_MEMORY), \
-				 errmsg("out of memory"))); \
 	if (found) \
 		elog(ERROR, "duplicate portal name"); \
 	hentry->portal = PORTAL; \

src/include/utils/hsearch.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/utils/hsearch.h,v 1.35 2005/04/14 20:32:43 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/utils/hsearch.h,v 1.36 2005/05/29 04:23:06 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -153,8 +153,7 @@ typedef enum
 	HASH_FIND,
 	HASH_ENTER,
 	HASH_REMOVE,
-	HASH_FIND_SAVE,
-	HASH_REMOVE_SAVED
+	HASH_ENTER_NULL
 } HASHACTION;
 
 /* hash_seq status (should be considered an opaque type by callers) */

src/pl/plpgsql/src/pl_comp.c

@@ -3,7 +3,7 @@
  *			  procedural language
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/pl/plpgsql/src/pl_comp.c,v 1.89 2005/05/06 17:24:55 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/pl/plpgsql/src/pl_comp.c,v 1.90 2005/05/29 04:23:06 tgl Exp $
  *
  *	  This software is copyrighted by Jan Wieck - Hamburg.
  *
@@ -2157,10 +2157,6 @@ plpgsql_HashTableInsert(PLpgSQL_function *function,
 											 (void *) func_key,
 											 HASH_ENTER,
 											 &found);
-	if (hentry == NULL)
-		ereport(ERROR,
-				(errcode(ERRCODE_OUT_OF_MEMORY),
-				 errmsg("out of memory")));
 	if (found)
 		elog(WARNING, "trying to insert a function that already exists");
 

src/timezone/pgtz.c

@@ -6,7 +6,7 @@
  * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/timezone/pgtz.c,v 1.31 2005/05/23 21:54:02 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/timezone/pgtz.c,v 1.32 2005/05/29 04:23:07 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -971,6 +971,7 @@ identify_system_timezone(void)
  * load and parse the TZ definition file every time it is selected.
  */
 static HTAB *timezone_cache = NULL;
+
 static bool
 init_timezone_hashtable(void)
 {
@@ -1013,15 +1014,19 @@ pg_tzset(const char *name)
 							  HASH_FIND,
 							  NULL);
 	if (tzp)
+	{
 		/* Timezone found in cache, nothing more to do */
 		return tzp;
+	}
 
 	if (tzload(name, &tz.state) != 0)
 	{
 		if (name[0] == ':' || tzparse(name, &tz.state, FALSE) != 0)
+		{
 			/* Unknown timezone. Fail our call instead of loading GMT! */
 			return NULL;
 		}
+	}
 
 	strcpy(tz.TZname, name);
 
@@ -1031,9 +1036,6 @@ pg_tzset(const char *name)
 					  HASH_ENTER,
 					  NULL);
 	
-	if (!tzp)
-		return NULL;
-	
 	strcpy(tzp->TZname, tz.TZname);
 	memcpy(&tzp->state, &tz.state, sizeof(tz.state));