prohibit_shutdown_backward_scans_v1.patch

diff --git a/src/backend/executor/execMain.c b/src/backend/executor/execMain.c
index 01e1a461804..480f3d71bf0 100644
--- a/src/backend/executor/execMain.c
+++ b/src/backend/executor/execMain.c
@@ -1726,8 +1726,11 @@ ExecutePlan(EState *estate,
 		 */
 		if (TupIsNull(slot))
 		{
-			/* Allow nodes to release or shut down resources. */
-			(void) ExecShutdownNode(planstate);
+			/*
+			 * Allow nodes to release or shut down resources.  See ExecLimit.
+			 */
+			if (!(estate->es_top_eflags & EXEC_FLAG_BACKWARD))
+				(void) ExecShutdownNode(planstate);
 			break;
 		}
 
@@ -1773,8 +1776,11 @@ ExecutePlan(EState *estate,
 		current_tuple_count++;
 		if (numberTuples && numberTuples == current_tuple_count)
 		{
-			/* Allow nodes to release or shut down resources. */
-			(void) ExecShutdownNode(planstate);
+			/*
+			 * Allow nodes to release or shut down resources.  See ExecLimit.
+			 */
+			if (!(estate->es_top_eflags & EXEC_FLAG_BACKWARD))
+				(void) ExecShutdownNode(planstate);
 			break;
 		}
 	}
diff --git a/src/backend/executor/nodeLimit.c b/src/backend/executor/nodeLimit.c
index 66ea6aa3c35..eb0ed83d19e 100644
--- a/src/backend/executor/nodeLimit.c
+++ b/src/backend/executor/nodeLimit.c
@@ -134,8 +134,16 @@ ExecLimit(PlanState *pstate)
 					node->position - node->offset >= node->count)
 				{
 					node->lstate = LIMIT_WINDOWEND;
-					/* Allow nodes to release or shut down resources. */
-					(void) ExecShutdownNode(outerPlan);
+
+					/*
+					 * Allow nodes to release or shut down resources.  We
+					 * don't shut down resources if backward scans are
+					 * possible as we might need those resources during such
+					 * scans.
+					 */
+					if (!(node->ps.state->es_top_eflags & EXEC_FLAG_BACKWARD))
+						(void) ExecShutdownNode(outerPlan);
+
 					return NULL;
 				}