Create a "fast path" for acquiring weak relation locks.

When an AccessShareLock, RowShareLock, or RowExclusiveLock is requested
on an unshared database relation, and we can verify that no conflicting
locks can possibly be present, record the lock in a per-backend queue,
stored within the PGPROC, rather than in the primary lock table.  This
eliminates a great deal of contention on the lock manager LWLocks.

This patch also refactors the interface between GetLockStatusData() and
pg_lock_status() to be a bit more abstract, so that we don't rely so
heavily on the lock manager's internal representation details.  The new
fast path lock structures don't have a LOCK or PROCLOCK structure to
return, so we mustn't depend on that for purposes of listing outstanding
locks.

Review by Jeff Davis.

1 files changed, 45 insertions, 42 deletions

diff --git a/src/backend/utils/adt/lockfuncs.c b/src/backend/utils/adt/lockfuncs.c
index 6d7d4f4fb0f..0d9f482f330 100644
--- a/src/backend/utils/adt/lockfuncs.c
+++ b/src/backend/utils/adt/lockfuncs.c
@@ -49,6 +49,8 @@ typedef struct
 	int			predLockIdx;	/* current index for pred lock */
 } PG_Lock_Status;
 
+/* Number of columns in pg_locks output */
+#define NUM_LOCK_STATUS_COLUMNS		15
 
 /*
  * VXIDGetDatum - Construct a text representation of a VXID
@@ -96,7 +98,7 @@ pg_lock_status(PG_FUNCTION_ARGS)
 
 		/* build tupdesc for result tuples */
 		/* this had better match pg_locks view in system_views.sql */
-		tupdesc = CreateTemplateTupleDesc(14, false);
+		tupdesc = CreateTemplateTupleDesc(NUM_LOCK_STATUS_COLUMNS, false);
 		TupleDescInitEntry(tupdesc, (AttrNumber) 1, "locktype",
 						   TEXTOID, -1, 0);
 		TupleDescInitEntry(tupdesc, (AttrNumber) 2, "database",
@@ -125,6 +127,8 @@ pg_lock_status(PG_FUNCTION_ARGS)
 						   TEXTOID, -1, 0);
 		TupleDescInitEntry(tupdesc, (AttrNumber) 14, "granted",
 						   BOOLOID, -1, 0);
+		TupleDescInitEntry(tupdesc, (AttrNumber) 15, "fastpath",
+						   BOOLOID, -1, 0);
 
 		funcctx->tuple_desc = BlessTupleDesc(tupdesc);
 
@@ -149,21 +153,17 @@ pg_lock_status(PG_FUNCTION_ARGS)
 
 	while (mystatus->currIdx < lockData->nelements)
 	{
-		PROCLOCK   *proclock;
-		LOCK	   *lock;
-		PGPROC	   *proc;
 		bool		granted;
 		LOCKMODE	mode = 0;
 		const char *locktypename;
 		char		tnbuf[32];
-		Datum		values[14];
-		bool		nulls[14];
+		Datum		values[NUM_LOCK_STATUS_COLUMNS];
+		bool		nulls[NUM_LOCK_STATUS_COLUMNS];
 		HeapTuple	tuple;
 		Datum		result;
+		LockInstanceData   *instance;
 
-		proclock = &(lockData->proclocks[mystatus->currIdx]);
-		lock = &(lockData->locks[mystatus->currIdx]);
-		proc = &(lockData->procs[mystatus->currIdx]);
+		instance = &(lockData->locks[mystatus->currIdx]);
 
 		/*
 		 * Look to see if there are any held lock modes in this PROCLOCK. If
@@ -171,14 +171,14 @@ pg_lock_status(PG_FUNCTION_ARGS)
 		 * again.
 		 */
 		granted = false;
-		if (proclock->holdMask)
+		if (instance->holdMask)
 		{
 			for (mode = 0; mode < MAX_LOCKMODES; mode++)
 			{
-				if (proclock->holdMask & LOCKBIT_ON(mode))
+				if (instance->holdMask & LOCKBIT_ON(mode))
 				{
 					granted = true;
-					proclock->holdMask &= LOCKBIT_OFF(mode);
+					instance->holdMask &= LOCKBIT_OFF(mode);
 					break;
 				}
 			}
@@ -190,10 +190,10 @@ pg_lock_status(PG_FUNCTION_ARGS)
 		 */
 		if (!granted)
 		{
-			if (proc->waitLock == proclock->tag.myLock)
+			if (instance->waitLockMode != NoLock)
 			{
 				/* Yes, so report it with proper mode */
-				mode = proc->waitLockMode;
+				mode = instance->waitLockMode;
 
 				/*
 				 * We are now done with this PROCLOCK, so advance pointer to
@@ -218,22 +218,22 @@ pg_lock_status(PG_FUNCTION_ARGS)
 		MemSet(values, 0, sizeof(values));
 		MemSet(nulls, false, sizeof(nulls));
 
-		if (lock->tag.locktag_type <= LOCKTAG_LAST_TYPE)
-			locktypename = LockTagTypeNames[lock->tag.locktag_type];
+		if (instance->locktag.locktag_type <= LOCKTAG_LAST_TYPE)
+			locktypename = LockTagTypeNames[instance->locktag.locktag_type];
 		else
 		{
 			snprintf(tnbuf, sizeof(tnbuf), "unknown %d",
-					 (int) lock->tag.locktag_type);
+					 (int) instance->locktag.locktag_type);
 			locktypename = tnbuf;
 		}
 		values[0] = CStringGetTextDatum(locktypename);
 
-		switch ((LockTagType) lock->tag.locktag_type)
+		switch ((LockTagType) instance->locktag.locktag_type)
 		{
 			case LOCKTAG_RELATION:
 			case LOCKTAG_RELATION_EXTEND:
-				values[1] = ObjectIdGetDatum(lock->tag.locktag_field1);
-				values[2] = ObjectIdGetDatum(lock->tag.locktag_field2);
+				values[1] = ObjectIdGetDatum(instance->locktag.locktag_field1);
+				values[2] = ObjectIdGetDatum(instance->locktag.locktag_field2);
 				nulls[3] = true;
 				nulls[4] = true;
 				nulls[5] = true;
@@ -243,9 +243,9 @@ pg_lock_status(PG_FUNCTION_ARGS)
 				nulls[9] = true;
 				break;
 			case LOCKTAG_PAGE:
-				values[1] = ObjectIdGetDatum(lock->tag.locktag_field1);
-				values[2] = ObjectIdGetDatum(lock->tag.locktag_field2);
-				values[3] = UInt32GetDatum(lock->tag.locktag_field3);
+				values[1] = ObjectIdGetDatum(instance->locktag.locktag_field1);
+				values[2] = ObjectIdGetDatum(instance->locktag.locktag_field2);
+				values[3] = UInt32GetDatum(instance->locktag.locktag_field3);
 				nulls[4] = true;
 				nulls[5] = true;
 				nulls[6] = true;
@@ -254,10 +254,10 @@ pg_lock_status(PG_FUNCTION_ARGS)
 				nulls[9] = true;
 				break;
 			case LOCKTAG_TUPLE:
-				values[1] = ObjectIdGetDatum(lock->tag.locktag_field1);
-				values[2] = ObjectIdGetDatum(lock->tag.locktag_field2);
-				values[3] = UInt32GetDatum(lock->tag.locktag_field3);
-				values[4] = UInt16GetDatum(lock->tag.locktag_field4);
+				values[1] = ObjectIdGetDatum(instance->locktag.locktag_field1);
+				values[2] = ObjectIdGetDatum(instance->locktag.locktag_field2);
+				values[3] = UInt32GetDatum(instance->locktag.locktag_field3);
+				values[4] = UInt16GetDatum(instance->locktag.locktag_field4);
 				nulls[5] = true;
 				nulls[6] = true;
 				nulls[7] = true;
@@ -265,7 +265,8 @@ pg_lock_status(PG_FUNCTION_ARGS)
 				nulls[9] = true;
 				break;
 			case LOCKTAG_TRANSACTION:
-				values[6] = TransactionIdGetDatum(lock->tag.locktag_field1);
+				values[6] =
+					TransactionIdGetDatum(instance->locktag.locktag_field1);
 				nulls[1] = true;
 				nulls[2] = true;
 				nulls[3] = true;
@@ -276,8 +277,8 @@ pg_lock_status(PG_FUNCTION_ARGS)
 				nulls[9] = true;
 				break;
 			case LOCKTAG_VIRTUALTRANSACTION:
-				values[5] = VXIDGetDatum(lock->tag.locktag_field1,
-										 lock->tag.locktag_field2);
+				values[5] = VXIDGetDatum(instance->locktag.locktag_field1,
+										 instance->locktag.locktag_field2);
 				nulls[1] = true;
 				nulls[2] = true;
 				nulls[3] = true;
@@ -291,10 +292,10 @@ pg_lock_status(PG_FUNCTION_ARGS)
 			case LOCKTAG_USERLOCK:
 			case LOCKTAG_ADVISORY:
 			default:			/* treat unknown locktags like OBJECT */
-				values[1] = ObjectIdGetDatum(lock->tag.locktag_field1);
-				values[7] = ObjectIdGetDatum(lock->tag.locktag_field2);
-				values[8] = ObjectIdGetDatum(lock->tag.locktag_field3);
-				values[9] = Int16GetDatum(lock->tag.locktag_field4);
+				values[1] = ObjectIdGetDatum(instance->locktag.locktag_field1);
+				values[7] = ObjectIdGetDatum(instance->locktag.locktag_field2);
+				values[8] = ObjectIdGetDatum(instance->locktag.locktag_field3);
+				values[9] = Int16GetDatum(instance->locktag.locktag_field4);
 				nulls[2] = true;
 				nulls[3] = true;
 				nulls[4] = true;
@@ -303,13 +304,14 @@ pg_lock_status(PG_FUNCTION_ARGS)
 				break;
 		}
 
-		values[10] = VXIDGetDatum(proc->backendId, proc->lxid);
-		if (proc->pid != 0)
-			values[11] = Int32GetDatum(proc->pid);
+		values[10] = VXIDGetDatum(instance->backend, instance->lxid);
+		if (instance->pid != 0)
+			values[11] = Int32GetDatum(instance->pid);
 		else
 			nulls[11] = true;
-		values[12] = CStringGetTextDatum(GetLockmodeName(LOCK_LOCKMETHOD(*lock), mode));
+		values[12] = CStringGetTextDatum(GetLockmodeName(instance->locktag.locktag_lockmethodid, mode));
 		values[13] = BoolGetDatum(granted);
+		values[14] = BoolGetDatum(instance->fastpath);
 
 		tuple = heap_form_tuple(funcctx->tuple_desc, values, nulls);
 		result = HeapTupleGetDatum(tuple);
@@ -327,8 +329,8 @@ pg_lock_status(PG_FUNCTION_ARGS)
 
 		PREDICATELOCKTARGETTAG *predTag = &(predLockData->locktags[mystatus->predLockIdx]);
 		SERIALIZABLEXACT *xact = &(predLockData->xacts[mystatus->predLockIdx]);
-		Datum		values[14];
-		bool		nulls[14];
+		Datum		values[NUM_LOCK_STATUS_COLUMNS];
+		bool		nulls[NUM_LOCK_STATUS_COLUMNS];
 		HeapTuple	tuple;
 		Datum		result;
 
@@ -374,11 +376,12 @@ pg_lock_status(PG_FUNCTION_ARGS)
 			nulls[11] = true;
 
 		/*
-		 * Lock mode. Currently all predicate locks are SIReadLocks, which are
-		 * always held (never waiting)
+		 * Lock mode. Currently all predicate locks are SIReadLocks, which
+		 * are always held (never waiting) and have no fast path
 		 */
 		values[12] = CStringGetTextDatum("SIReadLock");
 		values[13] = BoolGetDatum(true);
+		values[14] = BoolGetDatum(false);
 
 		tuple = heap_form_tuple(funcctx->tuple_desc, values, nulls);
 		result = HeapTupleGetDatum(tuple);