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.

7 files changed, 13 insertions, 43 deletions

diff --git a/src/backend/storage/buffer/buf_table.c b/src/backend/storage/buffer/buf_table.c
index 7fe9e83477..5ef277edc9 100644
--- a/src/backend/storage/buffer/buf_table.c
+++ b/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;
 
diff --git a/src/backend/storage/buffer/localbuf.c b/src/backend/storage/buffer/localbuf.c
index 0e9e7b68cc..a2604dcf55 100644
--- a/src/backend/storage/buffer/localbuf.c
+++ b/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;
diff --git a/src/backend/storage/freespace/freespace.c b/src/backend/storage/freespace/freespace.c
index b5cb8ef713..27e9952b3f 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 1.44 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)
 	{
diff --git a/src/backend/storage/ipc/shmem.c b/src/backend/storage/ipc/shmem.c
index ca4ca19340..9af059139e 100644
--- a/src/backend/storage/ipc/shmem.c
+++ b/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)
diff --git a/src/backend/storage/lmgr/lock.c b/src/backend/storage/lmgr/lock.c
index 49843b2de6..d7180d7c1f 100644
--- a/src/backend/storage/lmgr/lock.c
+++ b/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 */
diff --git a/src/backend/storage/smgr/md.c b/src/backend/storage/smgr/md.c
index 73194ec4ef..1c0cb7e240 100644
--- a/src/backend/storage/smgr/md.c
+++ b/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)
-			return true;
-		/* out of memory: fall through to do it locally */
+		(void) hash_search(pendingOpsTable, &entry, HASH_ENTER, NULL);
+		return true;
 	}
 	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);
 }
 
 /*
diff --git a/src/backend/storage/smgr/smgr.c b/src/backend/storage/smgr/smgr.c
index 5abfc6d477..0b5a7154d3 100644
--- a/src/backend/storage/smgr/smgr.c
+++ b/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)