diff --git a/src/backend/catalog/partition.c b/src/backend/catalog/partition.c
index 9777d40e66..3a8306a055 100644
--- a/src/backend/catalog/partition.c
+++ b/src/backend/catalog/partition.c
@@ -953,7 +953,25 @@ check_default_allows_bound(Relation parent, Relation default_rel,
 
 		/* Lock already taken above. */
 		if (part_relid != RelationGetRelid(default_rel))
+		{
 			part_rel = heap_open(part_relid, NoLock);
+
+			/*
+			 * If the partition constraints on default partition child imply
+			 * that it will not contain any row that would belong to the new
+			 * partition, we can avoid scanning the child table.
+			 */
+			if (PartConstraintImpliedByRelConstraint(part_rel,
+													 def_part_constraints))
+			{
+				ereport(INFO,
+						(errmsg("partition constraint for table \"%s\" is implied by existing constraints",
+								RelationGetRelationName(part_rel))));
+
+				heap_close(part_rel, NoLock);
+				continue;
+			}
+		}
 		else
 			part_rel = default_rel;
 
diff --git a/src/test/regress/expected/alter_table.out b/src/test/regress/expected/alter_table.out
index cda8ce556c..dbe438dcd4 100644
--- a/src/test/regress/expected/alter_table.out
+++ b/src/test/regress/expected/alter_table.out
@@ -3474,9 +3474,10 @@ DETAIL:  "part_5" is already a child of "list_parted2".
 ALTER TABLE list_parted2 ATTACH PARTITION list_parted2 FOR VALUES IN (0);
 ERROR:  circular inheritance not allowed
 DETAIL:  "list_parted2" is already a child of "list_parted2".
--- If the partitioned table being attached does not have a constraint that
--- would allow validation scan to be skipped, but an individual partition
--- does, then the partition's validation scan is skipped.
+-- If a partitioned table being created or an existing table being attached
+-- as a paritition does not have a constraint that would allow validation scan
+-- to be skipped, but an individual partition does, then the partition's
+-- validation scan is skipped.
 CREATE TABLE quuux (a int, b text) PARTITION BY LIST (a);
 CREATE TABLE quuux_default PARTITION OF quuux DEFAULT PARTITION BY LIST (b);
 CREATE TABLE quuux_default1 PARTITION OF quuux_default (
@@ -3487,6 +3488,11 @@ ALTER TABLE quuux ATTACH PARTITION quuux1 FOR VALUES IN (1); -- validate!
 CREATE TABLE quuux2 (a int, b text);
 ALTER TABLE quuux ATTACH PARTITION quuux2 FOR VALUES IN (2); -- skip validation
 INFO:  updated partition constraint for default partition "quuux_default1" is implied by existing constraints
+DROP TABLE quuux1, quuux2;
+-- should validate for quuux1, but not for quuux2
+CREATE TABLE quuux1 PARTITION OF quuux FOR VALUES IN (1);
+CREATE TABLE quuux2 PARTITION OF quuux FOR VALUES IN (2);
+INFO:  partition constraint for table "quuux_default1" is implied by existing constraints
 DROP TABLE quuux;
 --
 -- DETACH PARTITION
diff --git a/src/test/regress/sql/alter_table.sql b/src/test/regress/sql/alter_table.sql
index d0daacf3e9..0c8ae2ab97 100644
--- a/src/test/regress/sql/alter_table.sql
+++ b/src/test/regress/sql/alter_table.sql
@@ -2285,9 +2285,10 @@ ALTER TABLE list_parted2 ATTACH PARTITION part_2 FOR VALUES IN (2);
 ALTER TABLE part_5 ATTACH PARTITION list_parted2 FOR VALUES IN ('b');
 ALTER TABLE list_parted2 ATTACH PARTITION list_parted2 FOR VALUES IN (0);
 
--- If the partitioned table being attached does not have a constraint that
--- would allow validation scan to be skipped, but an individual partition
--- does, then the partition's validation scan is skipped.
+-- If a partitioned table being created or an existing table being attached
+-- as a paritition does not have a constraint that would allow validation scan
+-- to be skipped, but an individual partition does, then the partition's
+-- validation scan is skipped.
 CREATE TABLE quuux (a int, b text) PARTITION BY LIST (a);
 CREATE TABLE quuux_default PARTITION OF quuux DEFAULT PARTITION BY LIST (b);
 CREATE TABLE quuux_default1 PARTITION OF quuux_default (
@@ -2297,6 +2298,10 @@ CREATE TABLE quuux1 (a int, b text);
 ALTER TABLE quuux ATTACH PARTITION quuux1 FOR VALUES IN (1); -- validate!
 CREATE TABLE quuux2 (a int, b text);
 ALTER TABLE quuux ATTACH PARTITION quuux2 FOR VALUES IN (2); -- skip validation
+DROP TABLE quuux1, quuux2;
+-- should validate for quuux1, but not for quuux2
+CREATE TABLE quuux1 PARTITION OF quuux FOR VALUES IN (1);
+CREATE TABLE quuux2 PARTITION OF quuux FOR VALUES IN (2);
 DROP TABLE quuux;
 
 --