Re: Support "Right Semi Join" plan shapes

     I did a simple test ,Subqueries of type (in) can be supported, There is a test sql that doesn't support it, and I think that's because it can't  pull up  the subqueries.

```

test=# explain (costs off) SELECT  t1.* FROM prt1_adv t1 WHERE EXISTS (SELECT 1 FROM prt2_adv t2 WHERE t1.a = t2.b) AND t1.b = 0 ORDER BY t1.a;
                      QUERY PLAN
------------------------------------------------------
 Sort
   Sort Key: t1.a
   ->  Hash Right Semi Join
         Hash Cond: (t2.b = t1.a)
         ->  Append
               ->  Seq Scan on prt2_adv_p1 t2_1
               ->  Seq Scan on prt2_adv_p2 t2_2
               ->  Seq Scan on prt2_adv_p3 t2_3
         ->  Hash
               ->  Append
                     ->  Seq Scan on prt1_adv_p1 t1_1
                           Filter: (b = 0)
                     ->  Seq Scan on prt1_adv_p2 t1_2
                           Filter: (b = 0)
                     ->  Seq Scan on prt1_adv_p3 t1_3
                           Filter: (b = 0)
(16 rows)

test=# explain (costs off) SELECT t1.* FROM prt1_adv t1 WHERE t1.a IN (SELECT t2.b FROM prt2_adv t2) AND t1.b = 0 ORDER BY t1.a;
                      QUERY PLAN
------------------------------------------------------
 Sort
   Sort Key: t1.a
   ->  Hash Right Semi Join
         Hash Cond: (t2.b = t1.a)
         ->  Append
               ->  Seq Scan on prt2_adv_p1 t2_1
               ->  Seq Scan on prt2_adv_p2 t2_2
               ->  Seq Scan on prt2_adv_p3 t2_3
         ->  Hash
               ->  Append
                     ->  Seq Scan on prt1_adv_p1 t1_1
                           Filter: (b = 0)
                     ->  Seq Scan on prt1_adv_p2 t1_2
                           Filter: (b = 0)
                     ->  Seq Scan on prt1_adv_p3 t1_3
                           Filter: (b = 0)
(16 rows)

test=#

test=# explain (costs off) SELECT t1.* FROM plt1_adv t1 WHERE EXISTS (SELECT 1 FROM plt2_adv t2 WHERE t1.a = t2.a AND t1.c = t2.c) AND t1.b < 10 ORDER BY t1.a;
                      QUERY PLAN
------------------------------------------------------
 Sort
   Sort Key: t1.a
   ->  Hash Right Semi Join
         Hash Cond: ((t2.a = t1.a) AND (t2.c = t1.c))
         ->  Append
               ->  Seq Scan on plt2_adv_p1 t2_1
               ->  Seq Scan on plt2_adv_p2 t2_2
               ->  Seq Scan on plt2_adv_p3 t2_3
         ->  Hash
               ->  Append
                     ->  Seq Scan on plt1_adv_p1 t1_1
                           Filter: (b < 10)
                     ->  Seq Scan on plt1_adv_p2 t1_2
                           Filter: (b < 10)
                     ->  Seq Scan on plt1_adv_p3 t1_3
                           Filter: (b < 10)
(16 rows)

test=#
test=# explain (costs off) SELECT t1.* FROM plt1_adv t1 WHERE (t1.a, t1.c) IN (SELECT t2.a, t2.c FROM plt2_adv t2) AND t1.b < 10 ORDER BY t1.a;
                      QUERY PLAN
------------------------------------------------------
 Sort
   Sort Key: t1.a
   ->  Hash Right Semi Join
         Hash Cond: ((t2.a = t1.a) AND (t2.c = t1.c))
         ->  Append
               ->  Seq Scan on plt2_adv_p1 t2_1
               ->  Seq Scan on plt2_adv_p2 t2_2
               ->  Seq Scan on plt2_adv_p3 t2_3
         ->  Hash
               ->  Append
                     ->  Seq Scan on plt1_adv_p1 t1_1
                           Filter: (b < 10)
                     ->  Seq Scan on plt1_adv_p2 t1_2
                           Filter: (b < 10)
                     ->  Seq Scan on plt1_adv_p3 t1_3
                           Filter: (b < 10)
(16 rows)

```

```

test=# explain (costs off) select * from int4_tbl i4, tenk1 a
 where exists(select * from tenk1 b
              where a.twothousand = b.twothousand and a.fivethous <> b.fivethous)
       and i4.f1 = a.tenthous;
                   QUERY PLAN
-------------------------------------------------
 Hash Right Semi Join
   Hash Cond: (b.twothousand = a.twothousand)
   Join Filter: (a.fivethous <> b.fivethous)
   ->  Seq Scan on tenk1 b
   ->  Hash
         ->  Hash Join
               Hash Cond: (a.tenthous = i4.f1)
               ->  Seq Scan on tenk1 a
               ->  Hash
                     ->  Seq Scan on int4_tbl i4
(10 rows)

test=# explain (costs off ) SELECT *
FROM int4_tbl i4, tenk1 a
WHERE (a.twothousand, a.fivethous) IN (
    SELECT b.twothousand, b.fivethous
    FROM tenk1 b
    WHERE a.twothousand = b.twothousand  and  a.fivethous <> b.fivethous
)
AND i4.f1 = a.tenthous;
                                       QUERY PLAN
----------------------------------------------------------------------------------------
 Nested Loop
   Join Filter: (i4.f1 = a.tenthous)
   ->  Seq Scan on tenk1 a
         Filter: (SubPlan 1)
         SubPlan 1
           ->  Seq Scan on tenk1 b
                 Filter: ((a.fivethous <> fivethous) AND (a.twothousand = twothousand))
   ->  Materialize
         ->  Seq Scan on int4_tbl i4
(9 rows)

test=# set enable_nestloop =off;
SET
test=# explain (costs off ) SELECT *
FROM int4_tbl i4, tenk1 a
WHERE (a.twothousand, a.fivethous) IN (
    SELECT b.twothousand, b.fivethous
    FROM tenk1 b
    WHERE a.twothousand = b.twothousand  and  a.fivethous <> b.fivethous
)
AND i4.f1 = a.tenthous;
                                       QUERY PLAN
----------------------------------------------------------------------------------------
 Hash Join
   Hash Cond: (a.tenthous = i4.f1)
   ->  Seq Scan on tenk1 a
         Filter: (SubPlan 1)
         SubPlan 1
           ->  Seq Scan on tenk1 b
                 Filter: ((a.fivethous <> fivethous) AND (a.twothousand = twothousand))
   ->  Hash
         ->  Seq Scan on int4_tbl i4
(9 rows)

```