fix_parallel_mode_nested_execution_v2.patch

diff --git a/src/backend/executor/execMain.c b/src/backend/executor/execMain.c
index 8359beb..09d1781 100644
--- a/src/backend/executor/execMain.c
+++ b/src/backend/executor/execMain.c
@@ -1703,7 +1703,14 @@ ExecutePlan(EState *estate,
 		use_parallel_mode = false;
 
 	if (use_parallel_mode)
+	{
 		EnterParallelMode();
+		estate->es_use_parallel_mode = true;
+	}
+	else
+	{
+		estate->es_use_parallel_mode = false;
+	}
 
 	/*
 	 * Loop until we've processed the proper number of tuples from the plan.
diff --git a/src/backend/executor/execUtils.c b/src/backend/executor/execUtils.c
index ee6c4af..e8c06c7 100644
--- a/src/backend/executor/execUtils.c
+++ b/src/backend/executor/execUtils.c
@@ -156,6 +156,8 @@ CreateExecutorState(void)
 	estate->es_epqScanDone = NULL;
 	estate->es_sourceText = NULL;
 
+	estate->es_use_parallel_mode = false;
+
 	/*
 	 * Return the executor state structure
 	 */
diff --git a/src/backend/executor/nodeGather.c b/src/backend/executor/nodeGather.c
index 8370037..639f4f5 100644
--- a/src/backend/executor/nodeGather.c
+++ b/src/backend/executor/nodeGather.c
@@ -150,7 +150,7 @@ ExecGather(PlanState *pstate)
 		 * Sometimes we might have to run without parallelism; but if parallel
 		 * mode is active then we can try to fire up some workers.
 		 */
-		if (gather->num_workers > 0 && IsInParallelMode())
+		if (gather->num_workers > 0 && estate->es_use_parallel_mode)
 		{
 			ParallelContext *pcxt;
 
diff --git a/src/backend/executor/nodeGatherMerge.c b/src/backend/executor/nodeGatherMerge.c
index 70f33a9..5625b12 100644
--- a/src/backend/executor/nodeGatherMerge.c
+++ b/src/backend/executor/nodeGatherMerge.c
@@ -194,7 +194,7 @@ ExecGatherMerge(PlanState *pstate)
 		 * Sometimes we might have to run without parallelism; but if parallel
 		 * mode is active then we can try to fire up some workers.
 		 */
-		if (gm->num_workers > 0 && IsInParallelMode())
+		if (gm->num_workers > 0 && estate->es_use_parallel_mode)
 		{
 			ParallelContext *pcxt;
 
diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h
index c461134..85313ab 100644
--- a/src/include/nodes/execnodes.h
+++ b/src/include/nodes/execnodes.h
@@ -507,6 +507,7 @@ typedef struct EState
 	bool	   *es_epqTupleSet; /* true if EPQ tuple is provided */
 	bool	   *es_epqScanDone; /* true if EPQ tuple has been fetched */
 
+	bool		es_use_parallel_mode; /* can we use parallel workers? */
 	/* The per-query shared memory area to use for parallel execution. */
 	struct dsa_area *es_query_dsa;
 } EState;