postgres
diff --git a/‎src/backend/executor/nodeHashjoin.c
Copy file name to clipboardExpand all lines: src/backend/executor/nodeHashjoin.c
+20-1Lines changed: 20 additions & 1 deletion b/‎src/backend/executor/nodeHashjoin.c
Copy file name to clipboardExpand all lines: src/backend/executor/nodeHashjoin.c
+20-1Lines changed: 20 additions & 1 deletion
@@ -454,7 +454,26 @@ ExecHashJoinImpl(PlanState *pstate, bool parallel)
 				if (joinqual == NULL || ExecQual(joinqual, econtext))
 				{
 					node->hj_MatchedOuter = true;
-					HeapTupleHeaderSetMatch(HJTUPLE_MINTUPLE(node->hj_CurTuple));
+
+					if (parallel)
+					{
+						/*
+						 * Full/right outer joins are currently not supported
+						 * for parallel joins, so we don't need to set the
+						 * match bit.  Experiments show that it's worth
+						 * avoiding the shared memory traffic on large
+						 * systems.
+						 */
+						Assert(!HJ_FILL_INNER(node));
+					}
+					else
+					{
+						/*
+						 * This is really only needed if HJ_FILL_INNER(node),
+						 * but we'll avoid the branch and just set it always.
+						 */
+						HeapTupleHeaderSetMatch(HJTUPLE_MINTUPLE(node->hj_CurTuple));
+					}
 
 					/* In an antijoin, we never return a matched tuple */
 					if (node->js.jointype == JOIN_ANTI)