diff --git a/src/backend/utils/adt/selfuncs.c b/src/backend/utils/adt/selfuncs.c
index 46c95b0..82a7f7f 100644
--- a/src/backend/utils/adt/selfuncs.c
+++ b/src/backend/utils/adt/selfuncs.c
@@ -3438,9 +3438,9 @@ estimate_num_groups(PlannerInfo *root, List *groupExprs, double input_rows,
 				reldistinct = clamp;
 
 			/*
-			 * Multiply by restriction selectivity.
+			 * Estimate number of distinct values expected in given number of rows.
 			 */
-			reldistinct *= rel->rows / rel->tuples;
+			reldistinct *= (1 - powl((reldistinct - 1) / reldistinct, rel->rows));
 
 			/*
 			 * Update estimate of total distinct groups.
diff --git a/src/test/regress/expected/join.out b/src/test/regress/expected/join.out
index 59d7877..d9dd5ca 100644
--- a/src/test/regress/expected/join.out
+++ b/src/test/regress/expected/join.out
@@ -3951,17 +3951,17 @@ select d.* from d left join (select * from b group by b.id, b.c_id) s
   on d.a = s.id;
               QUERY PLAN               
 ---------------------------------------
- Merge Left Join
-   Merge Cond: (d.a = s.id)
-   ->  Sort
-         Sort Key: d.a
-         ->  Seq Scan on d
+ Merge Right Join
+   Merge Cond: (s.id = d.a)
    ->  Sort
          Sort Key: s.id
          ->  Subquery Scan on s
                ->  HashAggregate
                      Group Key: b.id
                      ->  Seq Scan on b
+   ->  Sort
+         Sort Key: d.a
+         ->  Seq Scan on d
 (11 rows)
 
 -- similarly, but keying off a DISTINCT clause
@@ -3970,17 +3970,17 @@ select d.* from d left join (select distinct * from b) s
   on d.a = s.id;
                  QUERY PLAN                  
 ---------------------------------------------
- Merge Left Join
-   Merge Cond: (d.a = s.id)
-   ->  Sort
-         Sort Key: d.a
-         ->  Seq Scan on d
+ Merge Right Join
+   Merge Cond: (s.id = d.a)
    ->  Sort
          Sort Key: s.id
          ->  Subquery Scan on s
                ->  HashAggregate
                      Group Key: b.id, b.c_id
                      ->  Seq Scan on b
+   ->  Sort
+         Sort Key: d.a
+         ->  Seq Scan on d
 (11 rows)
 
 -- check join removal works when uniqueness of the join condition is enforced
diff --git a/src/test/regress/expected/subselect.out b/src/test/regress/expected/subselect.out
index de64ca7..0fc93d9 100644
--- a/src/test/regress/expected/subselect.out
+++ b/src/test/regress/expected/subselect.out
@@ -807,27 +807,24 @@ select * from int4_tbl where
 explain (verbose, costs off)
 select * from int4_tbl o where (f1, f1) in
   (select f1, generate_series(1,2) / 10 g from int4_tbl i group by f1);
-                              QUERY PLAN                              
-----------------------------------------------------------------------
- Hash Join
+                           QUERY PLAN                           
+----------------------------------------------------------------
+ Hash Semi Join
    Output: o.f1
    Hash Cond: (o.f1 = "ANY_subquery".f1)
    ->  Seq Scan on public.int4_tbl o
          Output: o.f1
    ->  Hash
          Output: "ANY_subquery".f1, "ANY_subquery".g
-         ->  HashAggregate
+         ->  Subquery Scan on "ANY_subquery"
                Output: "ANY_subquery".f1, "ANY_subquery".g
-               Group Key: "ANY_subquery".f1, "ANY_subquery".g
-               ->  Subquery Scan on "ANY_subquery"
-                     Output: "ANY_subquery".f1, "ANY_subquery".g
-                     Filter: ("ANY_subquery".f1 = "ANY_subquery".g)
-                     ->  HashAggregate
-                           Output: i.f1, (generate_series(1, 2) / 10)
-                           Group Key: i.f1
-                           ->  Seq Scan on public.int4_tbl i
-                                 Output: i.f1
-(18 rows)
+               Filter: ("ANY_subquery".f1 = "ANY_subquery".g)
+               ->  HashAggregate
+                     Output: i.f1, (generate_series(1, 2) / 10)
+                     Group Key: i.f1
+                     ->  Seq Scan on public.int4_tbl i
+                           Output: i.f1
+(15 rows)
 
 select * from int4_tbl o where (f1, f1) in
   (select f1, generate_series(1,2) / 10 g from int4_tbl i group by f1);
diff --git a/src/test/regress/expected/union.out b/src/test/regress/expected/union.out
index 016571b..f2e297e 100644
--- a/src/test/regress/expected/union.out
+++ b/src/test/regress/expected/union.out
@@ -263,16 +263,16 @@ ORDER BY 1;
 SELECT q2 FROM int8_tbl INTERSECT SELECT q1 FROM int8_tbl;
         q2        
 ------------------
- 4567890123456789
               123
+ 4567890123456789
 (2 rows)
 
 SELECT q2 FROM int8_tbl INTERSECT ALL SELECT q1 FROM int8_tbl;
         q2        
 ------------------
+              123
  4567890123456789
  4567890123456789
-              123
 (3 rows)
 
 SELECT q2 FROM int8_tbl EXCEPT SELECT q1 FROM int8_tbl ORDER BY 1;
@@ -305,16 +305,16 @@ SELECT q1 FROM int8_tbl EXCEPT SELECT q2 FROM int8_tbl;
 SELECT q1 FROM int8_tbl EXCEPT ALL SELECT q2 FROM int8_tbl;
         q1        
 ------------------
- 4567890123456789
               123
+ 4567890123456789
 (2 rows)
 
 SELECT q1 FROM int8_tbl EXCEPT ALL SELECT DISTINCT q2 FROM int8_tbl;
         q1        
 ------------------
+              123
  4567890123456789
  4567890123456789
-              123
 (3 rows)
 
 SELECT q1 FROM int8_tbl EXCEPT ALL SELECT q1 FROM int8_tbl FOR NO KEY UPDATE;
@@ -343,8 +343,8 @@ SELECT f1 FROM float8_tbl EXCEPT SELECT f1 FROM int4_tbl ORDER BY 1;
 SELECT q1 FROM int8_tbl INTERSECT SELECT q2 FROM int8_tbl UNION ALL SELECT q2 FROM int8_tbl;
         q1         
 -------------------
-  4567890123456789
                123
+  4567890123456789
                456
   4567890123456789
                123
@@ -355,15 +355,15 @@ SELECT q1 FROM int8_tbl INTERSECT SELECT q2 FROM int8_tbl UNION ALL SELECT q2 FR
 SELECT q1 FROM int8_tbl INTERSECT (((SELECT q2 FROM int8_tbl UNION ALL SELECT q2 FROM int8_tbl)));
         q1        
 ------------------
- 4567890123456789
               123
+ 4567890123456789
 (2 rows)
 
 (((SELECT q1 FROM int8_tbl INTERSECT SELECT q2 FROM int8_tbl))) UNION ALL SELECT q2 FROM int8_tbl;
         q1         
 -------------------
-  4567890123456789
                123
+  4567890123456789
                456
   4567890123456789
                123
@@ -419,8 +419,8 @@ HINT:  There is a column named "q2" in table "*SELECT* 2", but it cannot be refe
 SELECT q1 FROM int8_tbl EXCEPT (((SELECT q2 FROM int8_tbl ORDER BY q2 LIMIT 1)));
         q1        
 ------------------
- 4567890123456789
               123
+ 4567890123456789
 (2 rows)
 
 --