@@ -1087,6 +1087,13 @@ ExecOnConflictUpdate(ModifyTableState *mtstate,
10871087test = heap_lock_tuple (relation ,& tuple ,estate -> es_output_cid ,
10881088lockmode ,LockWaitBlock , false,& buffer ,
10891089& hufd );
1090+ /*
1091+ * We must hold share lock on the buffer content while examining tuple
1092+ * visibility. Afterwards, however, the tuples we have found to be
1093+ * visible are guaranteed good as long as we hold the buffer pin.
1094+ */
1095+ LockBuffer (buffer ,BUFFER_LOCK_SHARE );
1096+
10901097switch (test )
10911098{
10921099case HeapTupleMayBeUpdated :
@@ -1142,6 +1149,7 @@ ExecOnConflictUpdate(ModifyTableState *mtstate,
11421149 * loop here, as the new version of the row might not conflict
11431150 * anymore, or the conflicting tuple has actually been deleted.
11441151 */
1152+ LockBuffer (buffer ,BUFFER_LOCK_UNLOCK );
11451153ReleaseBuffer (buffer );
11461154return false;
11471155
@@ -1175,6 +1183,8 @@ ExecOnConflictUpdate(ModifyTableState *mtstate,
11751183/* Store target's existing tuple in the state's dedicated slot */
11761184ExecStoreTuple (& tuple ,mtstate -> mt_existing ,buffer , false);
11771185
1186+ LockBuffer (buffer ,BUFFER_LOCK_UNLOCK );
1187+
11781188/*
11791189 * Make tuple and any needed join variables available to ExecQual and
11801190 * ExecProject. The EXCLUDED tuple is installed in ecxt_innertuple, while