2 files changed, 31 insertions, 5 deletions
diff --git a/src/backend/executor/nodeGather.c b/src/backend/executor/nodeGather.c
index e45e07f0a1a..c979a557749 100644
--- a/src/backend/executor/nodeGather.c
+++ b/src/backend/executor/nodeGather.c
@@ -91,10 +91,14 @@ ExecInitGather(Gather *node, EState *estate, int eflags)
 	outerPlanState(gatherstate) = ExecInitNode(outerNode, estate, eflags);
 	tupDesc = ExecGetResultType(outerPlanState(gatherstate));
 
-	/* this node uses tuples from the tuple queue as scan slot */
-	gatherstate->ps.scanops = &TTSOpsHeapTuple;
-	gatherstate->ps.scanopsfixed = true;
-	gatherstate->ps.scanopsset = true;
+	/*
+	 * Leader may access ExecProcNode result directly (if
+	 * need_to_scan_locally), or from workers via tuple queue.  So we can't
+	 * trivially rely on the slot type being fixed for expressions evaluated
+	 * within this node.
+	 */
+	gatherstate->ps.outeropsset = true;
+	gatherstate->ps.outeropsfixed = false;
 
 	/*
 	 * Initialize result type and projection.
@@ -103,6 +107,16 @@ ExecInitGather(Gather *node, EState *estate, int eflags)
 	ExecConditionalAssignProjectionInfo(&gatherstate->ps, tupDesc, OUTER_VAR);
 
 	/*
+	 * Without projections result slot type is not trivially known, see
+	 * comment above.
+	 */
+	if (gatherstate->ps.ps_ProjInfo == NULL)
+	{
+		gatherstate->ps.resultopsset = true;
+		gatherstate->ps.resultopsfixed = false;
+	}
+
+	/*
 	 * Initialize funnel slot to same tuple descriptor as outer plan.
 	 */
 	gatherstate->funnel_slot = ExecInitExtraTupleSlot(estate, tupDesc,
diff --git a/src/backend/executor/nodeGatherMerge.c b/src/backend/executor/nodeGatherMerge.c
index 651565123be..51d910bd5ee 100644
--- a/src/backend/executor/nodeGatherMerge.c
+++ b/src/backend/executor/nodeGatherMerge.c
@@ -110,6 +110,15 @@ ExecInitGatherMerge(GatherMerge *node, EState *estate, int eflags)
 	outerPlanState(gm_state) = ExecInitNode(outerNode, estate, eflags);
 
 	/*
+	 * Leader may access ExecProcNode result directly (if
+	 * need_to_scan_locally), or from workers via tuple queue.  So we can't
+	 * trivially rely on the slot type being fixed for expressions evaluated
+	 * within this node.
+	 */
+	gm_state->ps.outeropsset = true;
+	gm_state->ps.outeropsfixed = false;
+
+	/*
 	 * Store the tuple descriptor into gather merge state, so we can use it
 	 * while initializing the gather merge slots.
 	 */
@@ -122,7 +131,10 @@ ExecInitGatherMerge(GatherMerge *node, EState *estate, int eflags)
 	ExecInitResultTypeTL(&gm_state->ps);
 	ExecConditionalAssignProjectionInfo(&gm_state->ps, tupDesc, OUTER_VAR);
 
-	/* leader accesses ExecProcNode result directly, others go through tuple queue */
+	/*
+	 * Without projections result slot type is not trivially known, see
+	 * comment above.
+	 */
 	if (gm_state->ps.ps_ProjInfo == NULL)
 	{
 		gm_state->ps.resultopsset = true;