v1-make-empty-bitmapsets-always-be-NULL.patch

diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c
index 7eb79cee58..a5d74cc462 100644
--- a/src/backend/access/heap/heapam.c
+++ b/src/backend/access/heap/heapam.c
@@ -3046,6 +3046,7 @@ heap_update(Relation relation, ItemPointer otid, HeapTuple newtup,
 	modified_attrs = HeapDetermineColumnsInfo(relation, interesting_attrs,
 											  id_attrs, &oldtup,
 											  newtup, &id_has_external);
+	interesting_attrs = NULL;	/* don't try to free it again */
 
 	/*
 	 * If we're not updating any "key" column, we can grab a weaker lock type.
@@ -3860,8 +3861,9 @@ heap_attr_equals(TupleDesc tupdesc, int attrnum, Datum value1, Datum value2,
  * listed as interesting) of the old tuple is a member of external_cols and is
  * stored externally.
  *
- * The input interesting_cols bitmapset is destructively modified; that is OK
- * since this is invoked at most once in heap_update.
+ * The input interesting_cols bitmapset is destructively modified, and freed
+ * before we return; that is OK since this is invoked at most once in
+ * heap_update.
  */
 static Bitmapset *
 HeapDetermineColumnsInfo(Relation relation,
diff --git a/src/backend/executor/execUtils.c b/src/backend/executor/execUtils.c
index c33a3c0bec..cfa95a07e4 100644
--- a/src/backend/executor/execUtils.c
+++ b/src/backend/executor/execUtils.c
@@ -877,15 +877,7 @@ UpdateChangedParamSet(PlanState *node, Bitmapset *newchg)
 	 * include anything else into its chgParam set.
 	 */
 	parmset = bms_intersect(node->plan->allParam, newchg);
-
-	/*
-	 * Keep node->chgParam == NULL if there's not actually any members; this
-	 * allows the simplest possible tests in executor node files.
-	 */
-	if (!bms_is_empty(parmset))
-		node->chgParam = bms_join(node->chgParam, parmset);
-	else
-		bms_free(parmset);
+	node->chgParam = bms_join(node->chgParam, parmset);
 }
 
 /*
diff --git a/src/backend/executor/nodeAgg.c b/src/backend/executor/nodeAgg.c
index 20d23696a5..51a30ddf65 100644
--- a/src/backend/executor/nodeAgg.c
+++ b/src/backend/executor/nodeAgg.c
@@ -1642,7 +1642,7 @@ find_hash_columns(AggState *aggstate)
 			perhash->hashGrpColIdxHash[i] = i + 1;
 			perhash->numhashGrpCols++;
 			/* delete already mapped columns */
-			bms_del_member(colnos, grpColIdx[i]);
+			colnos = bms_del_member(colnos, grpColIdx[i]);
 		}
 
 		/* and add the remaining columns */
@@ -1673,7 +1673,6 @@ find_hash_columns(AggState *aggstate)
 							   &TTSOpsMinimalTuple);
 
 		list_free(hashTlist);
-		bms_free(colnos);
 	}
 
 	bms_free(base_colnos);
diff --git a/src/backend/executor/nodeAppend.c b/src/backend/executor/nodeAppend.c
index cb25499b3f..c185b11c67 100644
--- a/src/backend/executor/nodeAppend.c
+++ b/src/backend/executor/nodeAppend.c
@@ -157,7 +157,10 @@ ExecInitAppend(Append *node, EState *estate, int eflags)
 		 * later calls to ExecFindMatchingSubPlans.
 		 */
 		if (!prunestate->do_exec_prune && nplans > 0)
+		{
 			appendstate->as_valid_subplans = bms_add_range(NULL, 0, nplans - 1);
+			appendstate->as_valid_subplans_identified = true;
+		}
 	}
 	else
 	{
@@ -170,6 +173,7 @@ ExecInitAppend(Append *node, EState *estate, int eflags)
 		Assert(nplans > 0);
 		appendstate->as_valid_subplans = validsubplans =
 			bms_add_range(NULL, 0, nplans - 1);
+		appendstate->as_valid_subplans_identified = true;
 		appendstate->as_prune_state = NULL;
 	}
 
@@ -259,7 +263,7 @@ ExecInitAppend(Append *node, EState *estate, int eflags)
 		appendstate->as_asyncresults = (TupleTableSlot **)
 			palloc0(nasyncplans * sizeof(TupleTableSlot *));
 
-		if (appendstate->as_valid_subplans != NULL)
+		if (appendstate->as_valid_subplans_identified)
 			classify_matching_subplans(appendstate);
 	}
 
@@ -414,13 +418,11 @@ ExecReScanAppend(AppendState *node)
 		bms_overlap(node->ps.chgParam,
 					node->as_prune_state->execparamids))
 	{
+		node->as_valid_subplans_identified = false;
 		bms_free(node->as_valid_subplans);
 		node->as_valid_subplans = NULL;
-		if (nasyncplans > 0)
-		{
-			bms_free(node->as_valid_asyncplans);
-			node->as_valid_asyncplans = NULL;
-		}
+		bms_free(node->as_valid_asyncplans);
+		node->as_valid_asyncplans = NULL;
 	}
 
 	for (i = 0; i < node->as_nplans; i++)
@@ -574,11 +576,14 @@ choose_next_subplan_locally(AppendState *node)
 		if (node->as_nasyncplans > 0)
 		{
 			/* We'd have filled as_valid_subplans already */
-			Assert(node->as_valid_subplans);
+			Assert(node->as_valid_subplans_identified);
 		}
-		else if (node->as_valid_subplans == NULL)
+		else if (!node->as_valid_subplans_identified)
+		{
 			node->as_valid_subplans =
 				ExecFindMatchingSubPlans(node->as_prune_state, false);
+			node->as_valid_subplans_identified = true;
+		}
 
 		whichplan = -1;
 	}
@@ -640,10 +645,11 @@ choose_next_subplan_for_leader(AppendState *node)
 		 * run-time pruning is disabled then the valid subplans will always be
 		 * set to all subplans.
 		 */
-		if (node->as_valid_subplans == NULL)
+		if (!node->as_valid_subplans_identified)
 		{
 			node->as_valid_subplans =
 				ExecFindMatchingSubPlans(node->as_prune_state, false);
+			node->as_valid_subplans_identified = true;
 
 			/*
 			 * Mark each invalid plan as finished to allow the loop below to
@@ -715,10 +721,12 @@ choose_next_subplan_for_worker(AppendState *node)
 	 * run-time pruning is disabled then the valid subplans will always be set
 	 * to all subplans.
 	 */
-	else if (node->as_valid_subplans == NULL)
+	else if (!node->as_valid_subplans_identified)
 	{
 		node->as_valid_subplans =
 			ExecFindMatchingSubPlans(node->as_prune_state, false);
+		node->as_valid_subplans_identified = true;
+
 		mark_invalid_subplans_as_finished(node);
 	}
 
@@ -866,10 +874,11 @@ ExecAppendAsyncBegin(AppendState *node)
 	Assert(node->as_nasyncplans > 0);
 
 	/* If we've yet to determine the valid subplans then do so now. */
-	if (node->as_valid_subplans == NULL)
+	if (!node->as_valid_subplans_identified)
 	{
 		node->as_valid_subplans =
 			ExecFindMatchingSubPlans(node->as_prune_state, false);
+		node->as_valid_subplans_identified = true;
 
 		classify_matching_subplans(node);
 	}
@@ -1143,6 +1152,7 @@ classify_matching_subplans(AppendState *node)
 {
 	Bitmapset  *valid_asyncplans;
 
+	Assert(node->as_valid_subplans_identified);
 	Assert(node->as_valid_asyncplans == NULL);
 
 	/* Nothing to do if there are no valid subplans. */
@@ -1161,9 +1171,8 @@ classify_matching_subplans(AppendState *node)
 	}
 
 	/* Get valid async subplans. */
-	valid_asyncplans = bms_copy(node->as_asyncplans);
-	valid_asyncplans = bms_int_members(valid_asyncplans,
-									   node->as_valid_subplans);
+	valid_asyncplans = bms_intersect(node->as_asyncplans,
+									 node->as_valid_subplans);
 
 	/* Adjust the valid subplans to contain sync subplans only. */
 	node->as_valid_subplans = bms_del_members(node->as_valid_subplans,
diff --git a/src/backend/nodes/bitmapset.c b/src/backend/nodes/bitmapset.c
index 98660524ad..af62a85980 100644
--- a/src/backend/nodes/bitmapset.c
+++ b/src/backend/nodes/bitmapset.c
@@ -5,10 +5,8 @@
  *
  * A bitmap set can represent any set of nonnegative integers, although
  * it is mainly intended for sets where the maximum value is not large,
- * say at most a few hundred.  By convention, a NULL pointer is always
- * accepted by all operations to represent the empty set.  (But beware
- * that this is not the only representation of the empty set.  Use
- * bms_is_empty() in preference to testing for NULL.)
+ * say at most a few hundred.  By convention, we always represent the
+ * empty set by a NULL pointer.
  *
  *
  * Copyright (c) 2003-2023, PostgreSQL Global Development Group
@@ -66,6 +64,8 @@
 #error "invalid BITS_PER_BITMAPWORD"
 #endif
 
+static bool bms_is_empty_internal(const Bitmapset *a);
+
 
 /*
  * bms_copy - make a palloc'd copy of a bitmapset
@@ -104,10 +104,10 @@ bms_equal(const Bitmapset *a, const Bitmapset *b)
 	{
 		if (b == NULL)
 			return true;
-		return bms_is_empty(b);
+		return false;
 	}
 	else if (b == NULL)
-		return bms_is_empty(a);
+		return false;
 	/* Identify shorter and longer input */
 	if (a->nwords <= b->nwords)
 	{
@@ -151,9 +151,9 @@ bms_compare(const Bitmapset *a, const Bitmapset *b)
 
 	/* Handle cases where either input is NULL */
 	if (a == NULL)
-		return bms_is_empty(b) ? 0 : -1;
+		return (b == NULL) ? 0 : -1;
 	else if (b == NULL)
-		return bms_is_empty(a) ? 0 : +1;
+		return +1;
 	/* Handle cases where one input is longer than the other */
 	shortlen = Min(a->nwords, b->nwords);
 	for (i = shortlen; i < a->nwords; i++)
@@ -282,6 +282,12 @@ bms_intersect(const Bitmapset *a, const Bitmapset *b)
 	resultlen = result->nwords;
 	for (i = 0; i < resultlen; i++)
 		result->words[i] &= other->words[i];
+	/* If we computed an empty result, we must return NULL */
+	if (bms_is_empty_internal(result))
+	{
+		pfree(result);
+		return NULL;
+	}
 	return result;
 }
 
@@ -300,12 +306,22 @@ bms_difference(const Bitmapset *a, const Bitmapset *b)
 		return NULL;
 	if (b == NULL)
 		return bms_copy(a);
+
+	/*
+	 * In Postgres' usage, an empty result is a very common case, so it's
+	 * worth optimizing for that by testing bms_nonempty_difference().  This
+	 * saves us a palloc/pfree cycle compared to checking after-the-fact.
+	 */
+	if (!bms_nonempty_difference(a, b))
+		return NULL;
+
 	/* Copy the left input */
 	result = bms_copy(a);
 	/* And remove b's bits from result */
 	shortlen = Min(a->nwords, b->nwords);
 	for (i = 0; i < shortlen; i++)
 		result->words[i] &= ~b->words[i];
+	/* Need not check for empty result, since we handled that case above */
 	return result;
 }
 
@@ -323,7 +339,7 @@ bms_is_subset(const Bitmapset *a, const Bitmapset *b)
 	if (a == NULL)
 		return true;			/* empty set is a subset of anything */
 	if (b == NULL)
-		return bms_is_empty(a);
+		return false;
 	/* Check common words */
 	shortlen = Min(a->nwords, b->nwords);
 	for (i = 0; i < shortlen; i++)
@@ -362,10 +378,10 @@ bms_subset_compare(const Bitmapset *a, const Bitmapset *b)
 	{
 		if (b == NULL)
 			return BMS_EQUAL;
-		return bms_is_empty(b) ? BMS_EQUAL : BMS_SUBSET1;
+		return BMS_SUBSET1;
 	}
 	if (b == NULL)
-		return bms_is_empty(a) ? BMS_EQUAL : BMS_SUBSET2;
+		return BMS_SUBSET2;
 	/* Check common words */
 	result = BMS_EQUAL;			/* status so far */
 	shortlen = Min(a->nwords, b->nwords);
@@ -554,7 +570,7 @@ bms_nonempty_difference(const Bitmapset *a, const Bitmapset *b)
 	if (a == NULL)
 		return false;
 	if (b == NULL)
-		return !bms_is_empty(a);
+		return true;
 	/* Check words in common */
 	shortlen = Min(a->nwords, b->nwords);
 	for (i = 0; i < shortlen; i++)
@@ -696,12 +712,13 @@ bms_membership(const Bitmapset *a)
 }
 
 /*
- * bms_is_empty - is a set empty?
+ * bms_is_empty_internal - is a set empty?
  *
- * This is even faster than bms_membership().
+ * This is now used only locally, to detect cases where a function has
+ * computed an empty set that we must now get rid of.
  */
-bool
-bms_is_empty(const Bitmapset *a)
+static bool
+bms_is_empty_internal(const Bitmapset *a)
 {
 	int			nwords;
 	int			wordnum;
@@ -786,6 +803,12 @@ bms_del_member(Bitmapset *a, int x)
 	bitnum = BITNUM(x);
 	if (wordnum < a->nwords)
 		a->words[wordnum] &= ~((bitmapword) 1 << bitnum);
+	/* If we computed an empty result, we must return NULL */
+	if (bms_is_empty_internal(a))
+	{
+		pfree(a);
+		return NULL;
+	}
 	return a;
 }
 
@@ -922,6 +945,12 @@ bms_int_members(Bitmapset *a, const Bitmapset *b)
 		a->words[i] &= b->words[i];
 	for (; i < a->nwords; i++)
 		a->words[i] = 0;
+	/* If we computed an empty result, we must return NULL */
+	if (bms_is_empty_internal(a))
+	{
+		pfree(a);
+		return NULL;
+	}
 	return a;
 }
 
@@ -943,6 +972,12 @@ bms_del_members(Bitmapset *a, const Bitmapset *b)
 	shortlen = Min(a->nwords, b->nwords);
 	for (i = 0; i < shortlen; i++)
 		a->words[i] &= ~b->words[i];
+	/* If we computed an empty result, we must return NULL */
+	if (bms_is_empty_internal(a))
+	{
+		pfree(a);
+		return NULL;
+	}
 	return a;
 }
 
@@ -985,7 +1020,8 @@ bms_join(Bitmapset *a, Bitmapset *b)
 /*
  * bms_first_member - find and remove first member of a set
  *
- * Returns -1 if set is empty.  NB: set is destructively modified!
+ * Returns -1 if set is empty.
+ * NB: set is destructively modified, and will be freed once empty!
  *
  * This is intended as support for iterating through the members of a set.
  * The typical pattern is
@@ -1021,6 +1057,8 @@ bms_first_member(Bitmapset *a)
 			return result;
 		}
 	}
+	/* Set is now empty, so it violates the empty-set invariant */
+	pfree(a);
 	return -1;
 }
 
diff --git a/src/backend/optimizer/path/indxpath.c b/src/backend/optimizer/path/indxpath.c
index 011a0337da..9f4698f2a2 100644
--- a/src/backend/optimizer/path/indxpath.c
+++ b/src/backend/optimizer/path/indxpath.c
@@ -949,9 +949,6 @@ build_index_paths(PlannerInfo *root, RelOptInfo *rel,
 
 	/* We do not want the index's rel itself listed in outer_relids */
 	outer_relids = bms_del_member(outer_relids, rel->relid);
-	/* Enforce convention that outer_relids is exactly NULL if empty */
-	if (bms_is_empty(outer_relids))
-		outer_relids = NULL;
 
 	/* Compute loop_count for cost estimation purposes */
 	loop_count = get_loop_count(root, rel->relid, outer_relids);
diff --git a/src/backend/optimizer/plan/subselect.c b/src/backend/optimizer/plan/subselect.c
index 04eda4798e..0956a33952 100644
--- a/src/backend/optimizer/plan/subselect.c
+++ b/src/backend/optimizer/plan/subselect.c
@@ -1486,7 +1486,6 @@ convert_EXISTS_sublink_to_join(PlannerInfo *root, SubLink *sublink,
 		if (varno <= rtoffset)
 			upper_varnos = bms_add_member(upper_varnos, varno);
 	}
-	bms_free(clause_varnos);
 	Assert(!bms_is_empty(upper_varnos));
 
 	/*
@@ -2824,15 +2823,6 @@ finalize_plan(PlannerInfo *root, Plan *plan,
 	/* but not any initplan setParams */
 	plan->extParam = bms_del_members(plan->extParam, initSetParam);
 
-	/*
-	 * For speed at execution time, make sure extParam/allParam are actually
-	 * NULL if they are empty sets.
-	 */
-	if (bms_is_empty(plan->extParam))
-		plan->extParam = NULL;
-	if (bms_is_empty(plan->allParam))
-		plan->allParam = NULL;
-
 	return plan->allParam;
 }
 
diff --git a/src/backend/optimizer/util/pathnode.c b/src/backend/optimizer/util/pathnode.c
index d749b50578..e8e06397a9 100644
--- a/src/backend/optimizer/util/pathnode.c
+++ b/src/backend/optimizer/util/pathnode.c
@@ -2372,12 +2372,6 @@ calc_nestloop_required_outer(Relids outerrelids,
 	/* ... and remove any mention of now-satisfied outer rels */
 	required_outer = bms_del_members(required_outer,
 									 outerrelids);
-	/* maintain invariant that required_outer is exactly NULL if empty */
-	if (bms_is_empty(required_outer))
-	{
-		bms_free(required_outer);
-		required_outer = NULL;
-	}
 	return required_outer;
 }
 
diff --git a/src/backend/optimizer/util/placeholder.c b/src/backend/optimizer/util/placeholder.c
index 9c6cb5eba7..b1723578e6 100644
--- a/src/backend/optimizer/util/placeholder.c
+++ b/src/backend/optimizer/util/placeholder.c
@@ -125,8 +125,6 @@ find_placeholder_info(PlannerInfo *root, PlaceHolderVar *phv)
 	 */
 	rels_used = pull_varnos(root, (Node *) phv->phexpr);
 	phinfo->ph_lateral = bms_difference(rels_used, phv->phrels);
-	if (bms_is_empty(phinfo->ph_lateral))
-		phinfo->ph_lateral = NULL;	/* make it exactly NULL if empty */
 	phinfo->ph_eval_at = bms_int_members(rels_used, phv->phrels);
 	/* If no contained vars, force evaluation at syntactic location */
 	if (bms_is_empty(phinfo->ph_eval_at))
diff --git a/src/backend/optimizer/util/relnode.c b/src/backend/optimizer/util/relnode.c
index 9ad44a0508..68fd033595 100644
--- a/src/backend/optimizer/util/relnode.c
+++ b/src/backend/optimizer/util/relnode.c
@@ -772,8 +772,6 @@ build_join_rel(PlannerInfo *root,
 	 */
 	joinrel->direct_lateral_relids =
 		bms_del_members(joinrel->direct_lateral_relids, joinrel->relids);
-	if (bms_is_empty(joinrel->direct_lateral_relids))
-		joinrel->direct_lateral_relids = NULL;
 
 	/*
 	 * Construct restrict and join clause lists for the new joinrel. (The
@@ -1024,11 +1022,6 @@ min_join_parameterization(PlannerInfo *root,
 	 */
 	result = bms_union(outer_rel->lateral_relids, inner_rel->lateral_relids);
 	result = bms_del_members(result, joinrelids);
-
-	/* Maintain invariant that result is exactly NULL if empty */
-	if (bms_is_empty(result))
-		result = NULL;
-
 	return result;
 }
 
diff --git a/src/backend/replication/logical/relation.c b/src/backend/replication/logical/relation.c
index 9f139c64db..7e32eee77e 100644
--- a/src/backend/replication/logical/relation.c
+++ b/src/backend/replication/logical/relation.c
@@ -214,6 +214,8 @@ logicalrep_rel_att_by_name(LogicalRepRelation *remoterel, const char *attname)
 
 /*
  * Report error with names of the missing local relation column(s), if any.
+ *
+ * Note that missingatts will be freed before we return.
  */
 static void
 logicalrep_report_missing_attrs(LogicalRepRelation *remoterel,
@@ -429,9 +431,6 @@ logicalrep_rel_open(LogicalRepRelId remoteid, LOCKMODE lockmode)
 
 		logicalrep_report_missing_attrs(remoterel, missingatts);
 
-		/* be tidy */
-		bms_free(missingatts);
-
 		/*
 		 * Set if the table's replica identity is enough to apply
 		 * update/delete.
diff --git a/src/backend/rewrite/rewriteManip.c b/src/backend/rewrite/rewriteManip.c
index 04718f66c0..d28d0da621 100644
--- a/src/backend/rewrite/rewriteManip.c
+++ b/src/backend/rewrite/rewriteManip.c
@@ -1247,16 +1247,11 @@ remove_nulling_relids_mutator(Node *node,
 			!bms_is_member(var->varno, context->except_relids) &&
 			bms_overlap(var->varnullingrels, context->removable_relids))
 		{
-			Relids		newnullingrels = bms_difference(var->varnullingrels,
-														context->removable_relids);
-
-			/* Micro-optimization: ensure nullingrels is NULL if empty */
-			if (bms_is_empty(newnullingrels))
-				newnullingrels = NULL;
 			/* Copy the Var ... */
 			var = copyObject(var);
 			/* ... and replace the copy's varnullingrels field */
-			var->varnullingrels = newnullingrels;
+			var->varnullingrels = bms_difference(var->varnullingrels,
+												 context->removable_relids);
 			return (Node *) var;
 		}
 		/* Otherwise fall through to copy the Var normally */
@@ -1268,26 +1263,20 @@ remove_nulling_relids_mutator(Node *node,
 		if (phv->phlevelsup == context->sublevels_up &&
 			!bms_overlap(phv->phrels, context->except_relids))
 		{
-			Relids		newnullingrels = bms_difference(phv->phnullingrels,
-														context->removable_relids);
-
 			/*
-			 * Micro-optimization: ensure nullingrels is NULL if empty.
-			 *
 			 * Note: it might seem desirable to remove the PHV altogether if
 			 * phnullingrels goes to empty.  Currently we dare not do that
 			 * because we use PHVs in some cases to enforce separate identity
 			 * of subexpressions; see wrap_non_vars usages in prepjointree.c.
 			 */
-			if (bms_is_empty(newnullingrels))
-				newnullingrels = NULL;
 			/* Copy the PlaceHolderVar and mutate what's below ... */
 			phv = (PlaceHolderVar *)
 				expression_tree_mutator(node,
 										remove_nulling_relids_mutator,
 										(void *) context);
 			/* ... and replace the copy's phnullingrels field */
-			phv->phnullingrels = newnullingrels;
+			phv->phnullingrels = bms_difference(phv->phnullingrels,
+												context->removable_relids);
 			/* We must also update phrels, if it contains a removable RTI */
 			phv->phrels = bms_difference(phv->phrels,
 										 context->removable_relids);
diff --git a/src/include/nodes/bitmapset.h b/src/include/nodes/bitmapset.h
index 3d2225e1ae..e1d6cabeba 100644
--- a/src/include/nodes/bitmapset.h
+++ b/src/include/nodes/bitmapset.h
@@ -5,10 +5,8 @@
  *
  * A bitmap set can represent any set of nonnegative integers, although
  * it is mainly intended for sets where the maximum value is not large,
- * say at most a few hundred.  By convention, a NULL pointer is always
- * accepted by all operations to represent the empty set.  (But beware
- * that this is not the only representation of the empty set.  Use
- * bms_is_empty() in preference to testing for NULL.)
+ * say at most a few hundred.  By convention, we always represent the
+ * empty set by a NULL pointer.
  *
  *
  * Copyright (c) 2003-2023, PostgreSQL Global Development Group
@@ -102,7 +100,9 @@ extern int	bms_num_members(const Bitmapset *a);
 
 /* optimized tests when we don't need to know exact membership count: */
 extern BMS_Membership bms_membership(const Bitmapset *a);
-extern bool bms_is_empty(const Bitmapset *a);
+
+/* NULL is now the only allowed representation of an empty bitmapset */
+#define bms_is_empty(a)  ((a) == NULL)
 
 /* these routines recycle (modify or free) their non-const inputs: */
 
diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h
index 20f4c8b35f..e7eb1e666f 100644
--- a/src/include/nodes/execnodes.h
+++ b/src/include/nodes/execnodes.h
@@ -1350,6 +1350,7 @@ struct AppendState
 	ParallelAppendState *as_pstate; /* parallel coordination info */
 	Size		pstate_len;		/* size of parallel coordination info */
 	struct PartitionPruneState *as_prune_state;
+	bool		as_valid_subplans_identified;	/* is as_valid_subplans valid? */
 	Bitmapset  *as_valid_subplans;
 	Bitmapset  *as_valid_asyncplans;	/* valid asynchronous plans indexes */
 	bool		(*choose_next_subplan) (AppendState *);
diff --git a/src/pl/plpgsql/src/pl_exec.c b/src/pl/plpgsql/src/pl_exec.c
index ffd6d2e3bc..b0a2cac227 100644
--- a/src/pl/plpgsql/src/pl_exec.c
+++ b/src/pl/plpgsql/src/pl_exec.c
@@ -6240,12 +6240,9 @@ setup_param_list(PLpgSQL_execstate *estate, PLpgSQL_expr *expr)
 	Assert(expr->plan != NULL);
 
 	/*
-	 * We only need a ParamListInfo if the expression has parameters.  In
-	 * principle we should test with bms_is_empty(), but we use a not-null
-	 * test because it's faster.  In current usage bits are never removed from
-	 * expr->paramnos, only added, so this test is correct anyway.
+	 * We only need a ParamListInfo if the expression has parameters.
 	 */
-	if (expr->paramnos)
+	if (!bms_is_empty(expr->paramnos))
 	{
 		/* Use the common ParamListInfo */
 		paramLI = estate->paramLI;