Restructure LOCKTAG as per discussions of a couple months ago.

Essentially, we shoehorn in a lockable-object-type field by taking a byte away from the lockmethodid, which can surely fit in one byte instead of two. This allows less artificial definitions of all the other fields of LOCKTAG; we can get rid of the special pg_xactlock pseudo-relation, and also support locks on individual tuples and general database objects (including shared objects). None of those possibilities are actually exploited just yet, however. I removed pg_xactlock from pg_class, but did not force initdb for that change. At this point, relkind 's' (SPECIAL) is unused and could be removed entirely.
2025-11-10 17:42:29 +03:00 · 2005-04-29 22:28:24 +00:00
parent 32d3b47e6f
commit 3a694bb0a1
14 changed files with 347 additions and 255 deletions
--- a/src/backend/access/heap/hio.c
+++ b/src/backend/access/heap/hio.c
@@ -8,7 +8,7 @@
 *
 *
 * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/access/heap/hio.c,v 1.54 2004/12/31 21:59:16 pgsql Exp $
+ *	  $PostgreSQL: pgsql/src/backend/access/heap/hio.c,v 1.55 2005/04/29 22:28:23 tgl Exp $
 *
 *-------------------------------------------------------------------------
 */
@@ -79,11 +79,6 @@ RelationPutHeapTuple(Relation relation,
 *	happen if space is freed in that page after heap_update finds there's not
 *	enough there).	In that case, the page will be pinned and locked only once.
 *
- *	Note that we use LockPage(rel, 0) to lock relation for extension.
- *	We can do this as long as in all other places we use page-level locking
- *	for indices only. Alternatively, we could define pseudo-table as
- *	we do for transactions with XactLockTable.
- *
 *	ereport(ERROR) is allowed here, so this routine *must* be called
 *	before any (unlogged) changes are made in buffer pool.
 */
@@ -235,7 +230,7 @@ RelationGetBufferForTuple(Relation relation, Size len,
 	needLock = !RELATION_IS_LOCAL(relation);

 	if (needLock)
-		LockPage(relation, 0, ExclusiveLock);
+		LockRelationForExtension(relation, ExclusiveLock);

 	/*
 	 * XXX This does an lseek - rather expensive - but at the moment it is
@@ -251,7 +246,7 @@ RelationGetBufferForTuple(Relation relation, Size len,
 	 * extend the relation some more.
 	 */
 	if (needLock)
-		UnlockPage(relation, 0, ExclusiveLock);
+		UnlockRelationForExtension(relation, ExclusiveLock);

 	/*
 	 * We can be certain that locking the otherBuffer first is OK, since
--- a/src/backend/access/nbtree/nbtpage.c
+++ b/src/backend/access/nbtree/nbtpage.c
@@ -9,7 +9,7 @@
 *
 *
 * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/access/nbtree/nbtpage.c,v 1.82 2005/03/22 06:17:03 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/access/nbtree/nbtpage.c,v 1.83 2005/04/29 22:28:24 tgl Exp $
 *
 *	NOTES
 *	   Postgres btree pages look like ordinary relation pages.	The opaque
@@ -487,7 +487,7 @@ _bt_getbuf(Relation rel, BlockNumber blkno, int access)
 		needLock = !RELATION_IS_LOCAL(rel);

 		if (needLock)
-			LockPage(rel, 0, ExclusiveLock);
+			LockRelationForExtension(rel, ExclusiveLock);

 		buf = ReadBuffer(rel, P_NEW);

@@ -496,7 +496,7 @@ _bt_getbuf(Relation rel, BlockNumber blkno, int access)
 		 * to extend the relation some more.
 		 */
 		if (needLock)
-			UnlockPage(rel, 0, ExclusiveLock);
+			UnlockRelationForExtension(rel, ExclusiveLock);

 		/* Acquire appropriate buffer lock on new page */
 		LockBuffer(buf, access);
--- a/src/backend/storage/lmgr/README
+++ b/src/backend/storage/lmgr/README
@@ -1,4 +1,4 @@
-$PostgreSQL: pgsql/src/backend/storage/lmgr/README,v 1.15 2004/08/27 17:07:41 tgl Exp $
+$PostgreSQL: pgsql/src/backend/storage/lmgr/README,v 1.16 2005/04/29 22:28:24 tgl Exp $


 LOCKING OVERVIEW
@@ -74,30 +74,14 @@ The lock manager's LOCK objects contain:

 tag -
    The key fields that are used for hashing locks in the shared memory
-    lock hash table.  This is declared as a separate struct to ensure that
-    we always zero out the correct number of bytes.  It is critical that
-    any alignment-padding bytes the compiler might insert in the struct
-    be zeroed out, else the hash computation will be random.
-
-    tag.relId -
-	Uniquely identifies the relation that the lock corresponds to.
-    
-    tag.dbId -
-	Uniquely identifies the database in which the relation lives.  If
-	this is a shared system relation (e.g. pg_database) the dbId must
-	be set to 0.
-
-    tag.objId -
-	Uniquely identifies the block/page within the relation and the
-	tuple within the block.  If we are setting a table level lock
-	both the blockId and tupleId (in an item pointer this is called
-	the position) are set to invalid, if it is a page level lock the
-	blockId is valid, while the tupleId is still invalid.  Finally if
-	this is a tuple level lock (we currently never do this) then both
-	the blockId and tupleId are set to valid specifications.  This is
-	how we get the appearance of a multi-level lock table while using
-	only a single table (see Gray's paper on 2 phase locking if
-	you are puzzled about how multi-level lock tables work).
+    lock hash table.  The contents of the tag essentially define an
+    individual lockable object.  See include/storage/lock.h for details
+    about the supported types of lockable objects.  This is declared as
+    a separate struct to ensure that we always zero out the correct number
+    of bytes.  It is critical that any alignment-padding bytes the compiler
+    might insert in the struct be zeroed out, else the hash computation
+    will be random.  (Currently, we are careful to define struct LOCKTAG
+    so that there are no padding bytes.)

 grantMask -
    This bitmask indicates what types of locks are currently held on the
--- a/src/backend/storage/lmgr/deadlock.c
+++ b/src/backend/storage/lmgr/deadlock.c
@@ -12,7 +12,7 @@
 *
 *
 * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/storage/lmgr/deadlock.c,v 1.33 2005/02/22 04:36:49 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/storage/lmgr/deadlock.c,v 1.34 2005/04/29 22:28:24 tgl Exp $
 *
 *	Interface:
 *
@@ -836,6 +836,69 @@ PrintLockQueue(LOCK *lock, const char *info)
 }
 #endif

+/*
+ * Append a description of a lockable object to buf.
+ *
+ * XXX probably this should be exported from lmgr.c or some such place.
+ */
+static void
+DescribeLockTag(StringInfo buf, const LOCKTAG *lock)
+{
+	switch (lock->locktag_type)
+	{
+		case LOCKTAG_RELATION:
+			appendStringInfo(buf,
+							 _("relation %u of database %u"),
+							 lock->locktag_field2,
+							 lock->locktag_field1);
+			break;
+		case LOCKTAG_RELATION_EXTEND:
+			appendStringInfo(buf,
+							 _("extension of relation %u of database %u"),
+							 lock->locktag_field2,
+							 lock->locktag_field1);
+			break;
+		case LOCKTAG_PAGE:
+			appendStringInfo(buf,
+							 _("page %u of relation %u of database %u"),
+							 lock->locktag_field3,
+							 lock->locktag_field2,
+							 lock->locktag_field1);
+			break;
+		case LOCKTAG_TUPLE:
+			appendStringInfo(buf,
+							 _("tuple (%u,%u) of relation %u of database %u"),
+							 lock->locktag_field3,
+							 lock->locktag_field4,
+							 lock->locktag_field2,
+							 lock->locktag_field1);
+			break;
+		case LOCKTAG_TRANSACTION:
+			appendStringInfo(buf,
+							 _("transaction %u"),
+							 lock->locktag_field1);
+			break;
+		case LOCKTAG_OBJECT:
+			appendStringInfo(buf,
+							 _("object %u of class %u of database %u"),
+							 lock->locktag_field3,
+							 lock->locktag_field2,
+							 lock->locktag_field1);
+			break;
+		case LOCKTAG_USERLOCK:
+			appendStringInfo(buf,
+							 _("user lock [%u,%u]"),
+							 lock->locktag_field1,
+							 lock->locktag_field2);
+			break;
+		default:
+			appendStringInfo(buf,
+							 _("unknown locktag type %d"),
+							 lock->locktag_type);
+			break;
+	}
+}
+
 /*
 * Report a detected deadlock, with available details.
 */
@@ -843,9 +906,12 @@ void
 DeadLockReport(void)
 {
 	StringInfoData buf;
+	StringInfoData buf2;
 	int			i;

 	initStringInfo(&buf);
+	initStringInfo(&buf2);
+
 	for (i = 0; i < nDeadlockDetails; i++)
 	{
 		DEADLOCK_INFO *info = &deadlockDetails[i];
@@ -860,27 +926,18 @@ DeadLockReport(void)
 		if (i > 0)
 			appendStringInfoChar(&buf, '\n');

-		if (info->locktag.relId == XactLockTableId && info->locktag.dbId == 0)
-		{
-			/* Lock is for transaction ID */
-			appendStringInfo(&buf,
-							 _("Process %d waits for %s on transaction %u; blocked by process %d."),
-							 info->pid,
-							 GetLockmodeName(info->lockmode),
-							 info->locktag.objId.xid,
-							 nextpid);
-		}
-		else
-		{
-			/* Lock is for a relation */
-			appendStringInfo(&buf,
-							 _("Process %d waits for %s on relation %u of database %u; blocked by process %d."),
-							 info->pid,
-							 GetLockmodeName(info->lockmode),
-							 info->locktag.relId,
-							 info->locktag.dbId,
-							 nextpid);
-		}
+		/* reset buf2 to hold next object description */
+		buf2.len = 0;
+		buf2.data[0] = '\0';
+
+		DescribeLockTag(&buf2, &info->locktag);
+
+		appendStringInfo(&buf,
+						 _("Process %d waits for %s on %s; blocked by process %d."),
+						 info->pid,
+						 GetLockmodeName(info->lockmode),
+						 buf2.data,
+						 nextpid);
 	}
 	ereport(ERROR,
 			(errcode(ERRCODE_T_R_DEADLOCK_DETECTED),
--- a/src/backend/storage/lmgr/lmgr.c
+++ b/src/backend/storage/lmgr/lmgr.c
@@ -8,7 +8,7 @@
 *
 *
 * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/storage/lmgr/lmgr.c,v 1.71 2004/12/31 22:01:05 pgsql Exp $
+ *	  $PostgreSQL: pgsql/src/backend/storage/lmgr/lmgr.c,v 1.72 2005/04/29 22:28:24 tgl Exp $
 *
 *-------------------------------------------------------------------------
 */
@@ -25,7 +25,10 @@
 #include "utils/inval.h"


-static LOCKMASK LockConflicts[] = {
+/*
+ * This conflict table defines the semantics of the various lock modes.
+ */
+static const LOCKMASK LockConflicts[] = {
 	0,

 	/* AccessShareLock */
@@ -69,6 +72,7 @@ static LOCKMASK LockConflicts[] = {

 static LOCKMETHODID LockTableId = INVALID_LOCKMETHOD;

+
 /*
 * Create the lock table described by LockConflicts
 */
@@ -96,11 +100,11 @@ InitLockTable(int maxBackends)
 #ifdef USER_LOCKS

 	/*
-	 * Allocate another tableId for long-term locks
+	 * Allocate another tableId for user locks (same shared hashtable though)
 	 */
 	LongTermTableId = LockMethodTableRename(LockTableId);
 	if (!LockMethodIsValid(LongTermTableId))
-		elog(ERROR, "could not rename long-term lock table");
+		elog(ERROR, "could not rename user lock table");
 	Assert(LongTermTableId == USER_LOCKMETHOD);
 #endif
 }
@@ -133,10 +137,9 @@ LockRelation(Relation relation, LOCKMODE lockmode)
 {
 	LOCKTAG		tag;

-	MemSet(&tag, 0, sizeof(tag));
-	tag.relId = relation->rd_lockInfo.lockRelId.relId;
-	tag.dbId = relation->rd_lockInfo.lockRelId.dbId;
-	tag.objId.blkno = InvalidBlockNumber;
+	SET_LOCKTAG_RELATION(tag,
+						 relation->rd_lockInfo.lockRelId.dbId,
+						 relation->rd_lockInfo.lockRelId.relId);

 	if (!LockAcquire(LockTableId, &tag, GetTopTransactionId(),
 					 lockmode, false))
@@ -167,10 +170,9 @@ ConditionalLockRelation(Relation relation, LOCKMODE lockmode)
 {
 	LOCKTAG		tag;

-	MemSet(&tag, 0, sizeof(tag));
-	tag.relId = relation->rd_lockInfo.lockRelId.relId;
-	tag.dbId = relation->rd_lockInfo.lockRelId.dbId;
-	tag.objId.blkno = InvalidBlockNumber;
+	SET_LOCKTAG_RELATION(tag,
+						 relation->rd_lockInfo.lockRelId.dbId,
+						 relation->rd_lockInfo.lockRelId.relId);

 	if (!LockAcquire(LockTableId, &tag, GetTopTransactionId(),
 					 lockmode, true))
@@ -197,10 +199,9 @@ UnlockRelation(Relation relation, LOCKMODE lockmode)
 {
 	LOCKTAG		tag;

-	MemSet(&tag, 0, sizeof(tag));
-	tag.relId = relation->rd_lockInfo.lockRelId.relId;
-	tag.dbId = relation->rd_lockInfo.lockRelId.dbId;
-	tag.objId.blkno = InvalidBlockNumber;
+	SET_LOCKTAG_RELATION(tag,
+						 relation->rd_lockInfo.lockRelId.dbId,
+						 relation->rd_lockInfo.lockRelId.relId);

 	LockRelease(LockTableId, &tag, GetTopTransactionId(), lockmode);
 }
@@ -222,10 +223,7 @@ LockRelationForSession(LockRelId *relid, LOCKMODE lockmode)
 {
 	LOCKTAG		tag;

-	MemSet(&tag, 0, sizeof(tag));
-	tag.relId = relid->relId;
-	tag.dbId = relid->dbId;
-	tag.objId.blkno = InvalidBlockNumber;
+	SET_LOCKTAG_RELATION(tag, relid->dbId, relid->relId);

 	if (!LockAcquire(LockTableId, &tag, InvalidTransactionId,
 					 lockmode, false))
@@ -240,30 +238,65 @@ UnlockRelationForSession(LockRelId *relid, LOCKMODE lockmode)
 {
 	LOCKTAG		tag;

-	MemSet(&tag, 0, sizeof(tag));
-	tag.relId = relid->relId;
-	tag.dbId = relid->dbId;
-	tag.objId.blkno = InvalidBlockNumber;
+	SET_LOCKTAG_RELATION(tag, relid->dbId, relid->relId);

 	LockRelease(LockTableId, &tag, InvalidTransactionId, lockmode);
 }

+/*
+ *		LockRelationForExtension
+ *
+ * This lock tag is used to interlock addition of pages to relations.
+ * We need such locking because bufmgr/smgr definition of P_NEW is not
+ * race-condition-proof.
+ *
+ * We assume the caller is already holding some type of regular lock on
+ * the relation, so no AcceptInvalidationMessages call is needed here.
+ */
+void
+LockRelationForExtension(Relation relation, LOCKMODE lockmode)
+{
+	LOCKTAG		tag;
+
+	SET_LOCKTAG_RELATION_EXTEND(tag,
+								relation->rd_lockInfo.lockRelId.dbId,
+								relation->rd_lockInfo.lockRelId.relId);
+
+	if (!LockAcquire(LockTableId, &tag, GetTopTransactionId(),
+					 lockmode, false))
+		elog(ERROR, "LockAcquire failed");
+}
+
+/*
+ *		UnlockRelationForExtension
+ */
+void
+UnlockRelationForExtension(Relation relation, LOCKMODE lockmode)
+{
+	LOCKTAG		tag;
+
+	SET_LOCKTAG_RELATION_EXTEND(tag,
+								relation->rd_lockInfo.lockRelId.dbId,
+								relation->rd_lockInfo.lockRelId.relId);
+
+	LockRelease(LockTableId, &tag, GetTopTransactionId(), lockmode);
+}
+
 /*
 *		LockPage
 *
 * Obtain a page-level lock.  This is currently used by some index access
- * methods to lock index pages.  For heap relations, it is used only with
- * blkno == 0 to signify locking the relation for extension.
+ * methods to lock individual index pages.
 */
 void
 LockPage(Relation relation, BlockNumber blkno, LOCKMODE lockmode)
 {
 	LOCKTAG		tag;

-	MemSet(&tag, 0, sizeof(tag));
-	tag.relId = relation->rd_lockInfo.lockRelId.relId;
-	tag.dbId = relation->rd_lockInfo.lockRelId.dbId;
-	tag.objId.blkno = blkno;
+	SET_LOCKTAG_PAGE(tag,
+					 relation->rd_lockInfo.lockRelId.dbId,
+					 relation->rd_lockInfo.lockRelId.relId,
+					 blkno);

 	if (!LockAcquire(LockTableId, &tag, GetTopTransactionId(),
 					 lockmode, false))
@@ -281,10 +314,10 @@ ConditionalLockPage(Relation relation, BlockNumber blkno, LOCKMODE lockmode)
 {
 	LOCKTAG		tag;

-	MemSet(&tag, 0, sizeof(tag));
-	tag.relId = relation->rd_lockInfo.lockRelId.relId;
-	tag.dbId = relation->rd_lockInfo.lockRelId.dbId;
-	tag.objId.blkno = blkno;
+	SET_LOCKTAG_PAGE(tag,
+					 relation->rd_lockInfo.lockRelId.dbId,
+					 relation->rd_lockInfo.lockRelId.relId,
+					 blkno);

 	return LockAcquire(LockTableId, &tag, GetTopTransactionId(),
 					   lockmode, true);
@@ -298,10 +331,10 @@ UnlockPage(Relation relation, BlockNumber blkno, LOCKMODE lockmode)
 {
 	LOCKTAG		tag;

-	MemSet(&tag, 0, sizeof(tag));
-	tag.relId = relation->rd_lockInfo.lockRelId.relId;
-	tag.dbId = relation->rd_lockInfo.lockRelId.dbId;
-	tag.objId.blkno = blkno;
+	SET_LOCKTAG_PAGE(tag,
+					 relation->rd_lockInfo.lockRelId.dbId,
+					 relation->rd_lockInfo.lockRelId.relId,
+					 blkno);

 	LockRelease(LockTableId, &tag, GetTopTransactionId(), lockmode);
 }
@@ -318,10 +351,7 @@ XactLockTableInsert(TransactionId xid)
 {
 	LOCKTAG		tag;

-	MemSet(&tag, 0, sizeof(tag));
-	tag.relId = XactLockTableId;
-	tag.dbId = InvalidOid;		/* xids are globally unique */
-	tag.objId.xid = xid;
+	SET_LOCKTAG_TRANSACTION(tag, xid);

 	if (!LockAcquire(LockTableId, &tag, GetTopTransactionId(),
 					 ExclusiveLock, false))
@@ -341,10 +371,7 @@ XactLockTableDelete(TransactionId xid)
 {
 	LOCKTAG		tag;

-	MemSet(&tag, 0, sizeof(tag));
-	tag.relId = XactLockTableId;
-	tag.dbId = InvalidOid;		/* xids are globally unique */
-	tag.objId.xid = xid;
+	SET_LOCKTAG_TRANSACTION(tag, xid);

 	LockRelease(LockTableId, &tag, GetTopTransactionId(), ExclusiveLock);
 }
@@ -372,10 +399,7 @@ XactLockTableWait(TransactionId xid)
 		Assert(TransactionIdIsValid(xid));
 		Assert(!TransactionIdEquals(xid, myxid));

-		MemSet(&tag, 0, sizeof(tag));
-		tag.relId = XactLockTableId;
-		tag.dbId = InvalidOid;
-		tag.objId.xid = xid;
+		SET_LOCKTAG_TRANSACTION(tag, xid);

 		if (!LockAcquire(LockTableId, &tag, myxid, ShareLock, false))
 			elog(ERROR, "LockAcquire failed");
--- 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 1.149 2005/04/13 18:54:56 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/storage/lmgr/lock.c,v 1.150 2005/04/29 22:28:24 tgl Exp $
 *
 * NOTES
 *	  Outside modules can create a lock table and acquire/release
@@ -108,10 +108,11 @@ inline static bool
 LOCK_DEBUG_ENABLED(const LOCK *lock)
 {
 	return
-		(((LOCK_LOCKMETHOD(*lock) == DEFAULT_LOCKMETHOD && Trace_locks)
-	   || (LOCK_LOCKMETHOD(*lock) == USER_LOCKMETHOD && Trace_userlocks))
-		 && (lock->tag.relId >= (Oid) Trace_lock_oidmin))
-		|| (Trace_lock_table && (lock->tag.relId == Trace_lock_table));
+		(((Trace_locks && LOCK_LOCKMETHOD(*lock) == DEFAULT_LOCKMETHOD)
+		  || (Trace_userlocks && LOCK_LOCKMETHOD(*lock) == USER_LOCKMETHOD))
+		 && ((Oid) lock->tag.locktag_field2 >= (Oid) Trace_lock_oidmin))
+		|| (Trace_lock_table
+			&& (lock->tag.locktag_field2 == Trace_lock_table));
 }


@@ -120,12 +121,14 @@ LOCK_PRINT(const char *where, const LOCK *lock, LOCKMODE type)
 {
 	if (LOCK_DEBUG_ENABLED(lock))
 		elog(LOG,
-			 "%s: lock(%lx) tbl(%d) rel(%u) db(%u) obj(%u) grantMask(%x) "
+			 "%s: lock(%lx) id(%u,%u,%u,%u,%u,%u) grantMask(%x) "
 			 "req(%d,%d,%d,%d,%d,%d,%d)=%d "
 			 "grant(%d,%d,%d,%d,%d,%d,%d)=%d wait(%d) type(%s)",
 			 where, MAKE_OFFSET(lock),
-			 lock->tag.lockmethodid, lock->tag.relId, lock->tag.dbId,
-			 lock->tag.objId.blkno, lock->grantMask,
+			 lock->tag.locktag_field1, lock->tag.locktag_field2,
+			 lock->tag.locktag_field3, lock->tag.locktag_field4,
+			 lock->tag.locktag_type, lock->tag.locktag_lockmethodid,
+			 lock->grantMask,
 			 lock->requested[1], lock->requested[2], lock->requested[3],
 			 lock->requested[4], lock->requested[5], lock->requested[6],
 			 lock->requested[7], lock->nRequested,
@@ -139,14 +142,9 @@ LOCK_PRINT(const char *where, const LOCK *lock, LOCKMODE type)
 inline static void
 PROCLOCK_PRINT(const char *where, const PROCLOCK *proclockP)
 {
-	if (
-		(((PROCLOCK_LOCKMETHOD(*proclockP) == DEFAULT_LOCKMETHOD && Trace_locks)
-		  || (PROCLOCK_LOCKMETHOD(*proclockP) == USER_LOCKMETHOD && Trace_userlocks))
-		 && (((LOCK *) MAKE_PTR(proclockP->tag.lock))->tag.relId >= (Oid) Trace_lock_oidmin))
-		|| (Trace_lock_table && (((LOCK *) MAKE_PTR(proclockP->tag.lock))->tag.relId == Trace_lock_table))
-		)
+	if (LOCK_DEBUG_ENABLED((LOCK *) MAKE_PTR(proclockP->tag.lock)))
 		elog(LOG,
-		"%s: proclock(%lx) lock(%lx) tbl(%d) proc(%lx) xid(%u) hold(%x)",
+		"%s: proclock(%lx) lock(%lx) method(%u) proc(%lx) xid(%u) hold(%x)",
 			 where, MAKE_OFFSET(proclockP), proclockP->tag.lock,
 			 PROCLOCK_LOCKMETHOD(*(proclockP)),
 			 proclockP->tag.proc, proclockP->tag.xid,
@@ -346,13 +344,9 @@ LockMethodTableInit(const char *tabName,
 * LockMethodTableRename -- allocate another lockmethod ID to the same
 *		lock table.
 *
- * NOTES: Both the lock module and the lock chain (lchain.c)
- *		module use table id's to distinguish between different
- *		kinds of locks.  Short term and long term locks look
- *		the same to the lock table, but are handled differently
- *		by the lock chain manager.	This function allows the
- *		client to use different lockmethods when acquiring/releasing
- *		short term and long term locks, yet store them all in one hashtable.
+ * NOTES: This function makes it possible to have different lockmethodids,
+ *		and hence different locking semantics, while still storing all
+ *		the data in one shared-memory hashtable.
 */

 LOCKMETHODID
@@ -404,33 +398,16 @@ LockMethodTableRename(LOCKMETHODID lockmethodid)
 *		the lock.  While the lock is active other clients can still
 *		read and write the tuple but they can be aware that it has
 *		been locked at the application level by someone.
- *		User locks use lock tags made of an uint16 and an uint32, for
- *		example 0 and a tuple oid, or any other arbitrary pair of
- *		numbers following a convention established by the application.
- *		In this sense tags don't refer to tuples or database entities.
+ *
 *		User locks and normal locks are completely orthogonal and
- *		they don't interfere with each other, so it is possible
- *		to acquire a normal lock on an user-locked tuple or user-lock
- *		a tuple for which a normal write lock already exists.
+ *		they don't interfere with each other.
+ *
 *		User locks are always non blocking, therefore they are never
 *		acquired if already held by another process.  They must be
 *		released explicitly by the application but they are released
 *		automatically when a backend terminates.
 *		They are indicated by a lockmethod 2 which is an alias for the
- *		normal lock table, and are distinguished from normal locks
- *		by the following differences:
- *
- *										normal lock		user lock
- *
- *		lockmethodid					1				2
- *		tag.dbId						database oid	database oid
- *		tag.relId						rel oid or 0	0
- *		tag.objId						block id		lock id2
- *										or xact id
- *		tag.offnum						0				lock id1
- *		proclock.xid					xid or 0		0
- *		persistence						transaction		user or backend
- *										or backend
+ *		normal lock table.
 *
 *		The lockmode parameter can have the same values for normal locks
 *		although probably only WRITE_LOCK can have some practical use.
@@ -456,13 +433,14 @@ LockAcquire(LOCKMETHODID lockmethodid, LOCKTAG *locktag,
 	int			i;

 #ifdef LOCK_DEBUG
-	if (lockmethodid == USER_LOCKMETHOD && Trace_userlocks)
-		elog(LOG, "LockAcquire: user lock [%u] %s",
-			 locktag->objId.blkno, lock_mode_names[lockmode]);
+	if (Trace_userlocks && lockmethodid == USER_LOCKMETHOD)
+		elog(LOG, "LockAcquire: user lock [%u,%u] %s",
+			 locktag->locktag_field1, locktag->locktag_field2,
+			 lock_mode_names[lockmode]);
 #endif

-	/* ???????? This must be changed when short term locks will be used */
-	locktag->lockmethodid = lockmethodid;
+	/* ugly */
+	locktag->locktag_lockmethodid = lockmethodid;

 	Assert(lockmethodid < NumLockMethods);
 	lockMethodTable = LockMethods[lockmethodid];
@@ -1231,12 +1209,14 @@ LockRelease(LOCKMETHODID lockmethodid, LOCKTAG *locktag,
 	bool		wakeupNeeded;

 #ifdef LOCK_DEBUG
-	if (lockmethodid == USER_LOCKMETHOD && Trace_userlocks)
-		elog(LOG, "LockRelease: user lock tag [%u] %d", locktag->objId.blkno, lockmode);
+	if (Trace_userlocks && lockmethodid == USER_LOCKMETHOD)
+		elog(LOG, "LockRelease: user lock [%u,%u] %s",
+			 locktag->locktag_field1, locktag->locktag_field2,
+			 lock_mode_names[lockmode]);
 #endif

-	/* ???????? This must be changed when short term locks will be used */
-	locktag->lockmethodid = lockmethodid;
+	/* ugly */
+	locktag->locktag_lockmethodid = lockmethodid;

 	Assert(lockmethodid < NumLockMethods);
 	lockMethodTable = LockMethods[lockmethodid];
--- a/src/backend/utils/adt/lockfuncs.c
+++ b/src/backend/utils/adt/lockfuncs.c
@@ -6,7 +6,7 @@
 * Copyright (c) 2002-2005, PostgreSQL Global Development Group
 *
 * IDENTIFICATION
- *		$PostgreSQL: pgsql/src/backend/utils/adt/lockfuncs.c,v 1.16 2005/01/01 05:43:07 momjian Exp $
+ *		$PostgreSQL: pgsql/src/backend/utils/adt/lockfuncs.c,v 1.17 2005/04/29 22:28:24 tgl Exp $
 *
 *-------------------------------------------------------------------------
 */
@@ -155,20 +155,24 @@ pg_lock_status(PG_FUNCTION_ARGS)
 		MemSet(values, 0, sizeof(values));
 		MemSet(nulls, ' ', sizeof(nulls));

-		if (lock->tag.relId == XactLockTableId && lock->tag.dbId == 0)
+		switch (lock->tag.locktag_type)
 		{
-			/* Lock is for transaction ID */
-			nulls[0] = 'n';
-			nulls[1] = 'n';
-			values[2] = TransactionIdGetDatum(lock->tag.objId.xid);
-		}
-		else
-		{
-			/* Lock is for a relation */
-			values[0] = ObjectIdGetDatum(lock->tag.relId);
-			values[1] = ObjectIdGetDatum(lock->tag.dbId);
-			nulls[2] = 'n';
-
+			case LOCKTAG_RELATION:
+			case LOCKTAG_RELATION_EXTEND:
+			case LOCKTAG_PAGE:
+			case LOCKTAG_TUPLE:
+				values[0] = ObjectIdGetDatum(lock->tag.locktag_field2);
+				values[1] = ObjectIdGetDatum(lock->tag.locktag_field1);
+				nulls[2] = 'n';
+				break;
+			case LOCKTAG_TRANSACTION:
+				nulls[0] = 'n';
+				nulls[1] = 'n';
+				values[2] = TransactionIdGetDatum(lock->tag.locktag_field1);
+				break;
+			default:
+				/* XXX Ignore all other lock types for now */
+				continue;
 		}

 		values[3] = Int32GetDatum(proc->pid);