3 files changed, 75 insertions, 2 deletions
diff --git a/src/backend/optimizer/plan/planner.c b/src/backend/optimizer/plan/planner.c
index eadc04222ef..401299e5420 100644
--- a/src/backend/optimizer/plan/planner.c
+++ b/src/backend/optimizer/plan/planner.c
@@ -3124,6 +3124,14 @@ remove_useless_groupby_columns(PlannerInfo *root)
 		if (rte->rtekind != RTE_RELATION)
 			continue;
 
+		/*
+		 * We must skip inheritance parent tables as some of the child rels
+		 * may cause duplicate rows.  This cannot happen with partitioned
+		 * tables, however.
+		 */
+		if (rte->inh && rte->relkind != RELKIND_PARTITIONED_TABLE)
+			continue;
+
 		/* Nothing to do unless this rel has multiple Vars in GROUP BY */
 		relattnos = groupbyattnos[relid];
 		if (bms_membership(relattnos) != BMS_MULTIPLE)
diff --git a/src/test/regress/expected/aggregates.out b/src/test/regress/expected/aggregates.out
index 2e5ce8cc32b..ef8eec3fbf2 100644
--- a/src/test/regress/expected/aggregates.out
+++ b/src/test/regress/expected/aggregates.out
@@ -1147,9 +1147,52 @@ explain (costs off) select * from t3 group by a,b,c;
    ->  Seq Scan on t3
 (3 rows)
 
-drop table t1;
+create temp table t1c () inherits (t1);
+-- Ensure we don't remove any columns when t1 has a child table
+explain (costs off) select * from t1 group by a,b,c,d;
+             QUERY PLAN              
+-------------------------------------
+ HashAggregate
+   Group Key: t1.a, t1.b, t1.c, t1.d
+   ->  Append
+         ->  Seq Scan on t1
+         ->  Seq Scan on t1c
+(5 rows)
+
+-- Okay to remove columns if we're only querying the parent.
+explain (costs off) select * from only t1 group by a,b,c,d;
+      QUERY PLAN      
+----------------------
+ HashAggregate
+   Group Key: a, b
+   ->  Seq Scan on t1
+(3 rows)
+
+create temp table p_t1 (
+  a int,
+  b int,
+  c int,
+  d int,
+  primary key(a,b)
+) partition by list(a);
+create temp table p_t1_1 partition of p_t1 for values in(1);
+create temp table p_t1_2 partition of p_t1 for values in(2);
+-- Ensure we can remove non-PK columns for partitioned tables.
+explain (costs off) select * from p_t1 group by a,b,c,d;
+           QUERY PLAN            
+---------------------------------
+ HashAggregate
+   Group Key: p_t1_1.a, p_t1_1.b
+   ->  Append
+         ->  Seq Scan on p_t1_1
+         ->  Seq Scan on p_t1_2
+(5 rows)
+
+drop table t1 cascade;
+NOTICE:  drop cascades to table t1c
 drop table t2;
 drop table t3;
+drop table p_t1;
 --
 -- Test combinations of DISTINCT and/or ORDER BY
 --
diff --git a/src/test/regress/sql/aggregates.sql b/src/test/regress/sql/aggregates.sql
index ca0d5e66b2a..17fb256aec5 100644
--- a/src/test/regress/sql/aggregates.sql
+++ b/src/test/regress/sql/aggregates.sql
@@ -406,9 +406,31 @@ group by t1.a,t1.b,t1.c,t1.d,t2.x,t2.z;
 -- Cannot optimize when PK is deferrable
 explain (costs off) select * from t3 group by a,b,c;
 
-drop table t1;
+create temp table t1c () inherits (t1);
+
+-- Ensure we don't remove any columns when t1 has a child table
+explain (costs off) select * from t1 group by a,b,c,d;
+
+-- Okay to remove columns if we're only querying the parent.
+explain (costs off) select * from only t1 group by a,b,c,d;
+
+create temp table p_t1 (
+  a int,
+  b int,
+  c int,
+  d int,
+  primary key(a,b)
+) partition by list(a);
+create temp table p_t1_1 partition of p_t1 for values in(1);
+create temp table p_t1_2 partition of p_t1 for values in(2);
+
+-- Ensure we can remove non-PK columns for partitioned tables.
+explain (costs off) select * from p_t1 group by a,b,c,d;
+
+drop table t1 cascade;
 drop table t2;
 drop table t3;
+drop table p_t1;
 
 --
 -- Test combinations of DISTINCT and/or ORDER BY