Don't follow update chains unless caller requests it

Some code paths must not follow chains -- they will be followed by the EvalPlanQual mechanism. Doing both causes deadlocks.
alvherre · Apr 2, 2012 · e00e682 · e00e682
1 parent 48cd8cc
commit e00e682
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Showing 5 changed files with 17 additions and 12 deletions.
diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c
@@ -3683,6 +3683,8 @@ get_mxact_status_for_lock(LockTupleMode mode, bool is_update)
  *		tuple's cmax if lock is successful)
  *	mode: indicates if shared or exclusive tuple lock is desired
  *	nowait: if true, ereport rather than blocking if lock not available
+ *	follow_updates: if true, follow the update chain to also lock descendant
+ *		tuples.
  *
  * Output parameters:
  *	*tuple: all fields filled in
@@ -3706,7 +3708,8 @@ get_mxact_status_for_lock(LockTupleMode mode, bool is_update)
 HTSU_Result
 heap_lock_tuple(Relation relation, HeapTuple tuple, Buffer *buffer,
 				ItemPointer ctid, TransactionId *update_xmax,
-				CommandId cid, LockTupleMode mode, bool nowait)
+				CommandId cid, LockTupleMode mode, bool nowait,
+				bool follow_updates)
 {
 	HTSU_Result result;
 	ItemPointer tid = &(tuple->t_self);
@@ -3845,10 +3848,12 @@ heap_lock_tuple(Relation relation, HeapTuple tuple, Buffer *buffer,
 		if ((mode == LockTupleKeyShare) &&
 			!(infomask2 & HEAP_UPDATE_KEY_REVOKED))
 		{
-			bool	not_updated = false;
+			bool	updated;
+
+			updated = !HeapTupleHeaderInfomaskIsOnlyLocked(infomask);
 
 			/* if there are updates, follow the update chain */
-			if (!HeapTupleHeaderInfomaskIsOnlyLocked(infomask))
+			if (follow_updates && updated)
 			{
 				HTSU_Result		res;
 
@@ -3863,8 +3868,6 @@ heap_lock_tuple(Relation relation, HeapTuple tuple, Buffer *buffer,
 					goto failed;
 				}
 			}
-			else
-				not_updated = true;
 
 			LockBuffer(*buffer, BUFFER_LOCK_EXCLUSIVE);
 
@@ -3876,7 +3879,7 @@ heap_lock_tuple(Relation relation, HeapTuple tuple, Buffer *buffer,
 			 */
 			if (!HeapTupleHeaderIsOnlyLocked(tuple->t_data) &&
 				((tuple->t_data->t_infomask2 & HEAP_UPDATE_KEY_REVOKED) ||
-				 not_updated))
+				 !updated))
 				goto l3;
 			require_sleep = false;
 
@@ -4013,7 +4016,8 @@ heap_lock_tuple(Relation relation, HeapTuple tuple, Buffer *buffer,
 					MultiXactIdWait((MultiXactId) xwait, status, &remain, infomask);
 
 				/* if there are updates, follow the update chain */
-				if (!HeapTupleHeaderInfomaskIsOnlyLocked(infomask))
+				if (follow_updates &&
+					!HeapTupleHeaderInfomaskIsOnlyLocked(infomask))
 				{
 					HTSU_Result		res;
 
@@ -4066,7 +4070,8 @@ heap_lock_tuple(Relation relation, HeapTuple tuple, Buffer *buffer,
 					XactLockTableWait(xwait);
 
 				/* if there are updates, follow the update chain */
-				if (!HeapTupleHeaderInfomaskIsOnlyLocked(infomask))
+				if (follow_updates &&
+					!HeapTupleHeaderInfomaskIsOnlyLocked(infomask))
 				{
 					HTSU_Result		res;
 

diff --git a/src/backend/commands/trigger.c b/src/backend/commands/trigger.c
@@ -2601,7 +2601,7 @@ ltrmark:;
 		test = heap_lock_tuple(relation, &tuple, &buffer,
 							   &update_ctid, &update_xmax,
 							   estate->es_output_cid,
-							   LockTupleUpdate, false);
+							   LockTupleUpdate, false, false);
 		switch (test)
 		{
 			case HeapTupleSelfUpdated:

diff --git a/src/backend/executor/execMain.c b/src/backend/executor/execMain.c
@@ -1861,7 +1861,7 @@ EvalPlanQualFetch(EState *estate, Relation relation, int lockmode,
 			test = heap_lock_tuple(relation, &tuple, &buffer,
 								   &update_ctid, &update_xmax,
 								   estate->es_output_cid,
-								   lockmode, false);
+								   lockmode, false, false);
 			/* We now have two pins on the buffer, get rid of one */
 			ReleaseBuffer(buffer);
 

diff --git a/src/backend/executor/nodeLockRows.c b/src/backend/executor/nodeLockRows.c
@@ -134,7 +134,7 @@ ExecLockRows(LockRowsState *node)
 		test = heap_lock_tuple(erm->relation, &tuple, &buffer,
 							   &update_ctid, &update_xmax,
 							   estate->es_output_cid,
-							   lockmode, erm->noWait);
+							   lockmode, erm->noWait, true);
 		ReleaseBuffer(buffer);
 		switch (test)
 		{

diff --git a/src/include/access/heapam.h b/src/include/access/heapam.h
@@ -120,7 +120,7 @@ extern HTSU_Result heap_update(Relation relation, ItemPointer otid,
 extern HTSU_Result heap_lock_tuple(Relation relation, HeapTuple tuple,
 				Buffer *buffer, ItemPointer ctid,
 				TransactionId *update_xmax, CommandId cid,
-				LockTupleMode mode, bool nowait);
+				LockTupleMode mode, bool nowait, bool follow_update);
 extern void heap_inplace_update(Relation relation, HeapTuple tuple);
 extern bool heap_freeze_tuple(HeapTupleHeader tuple, TransactionId cutoff_xid,
 				  TransactionId cutoff_multi, Buffer buf);