BUG #14685: use ctid filter tuples will generate LOOP, very very slow

The following bug has been logged on the website:

Bug reference: 14685
Logged by: Zhou Digoal
Email address: digoal(at)126(dot)com
PostgreSQL version: 10beta1
Operating system: CentOS 6.x x64
Description:

test case

```
create table test1(c1 int, c2 int);
insert into test1 select random()*1000, random()*1000 from
generate_series(1,10000);
```

when use ctid not in , there is LOOP with Materialize.

```
postgres=# explain (analyze,verbose,timing,costs,buffers) select * from
test1 where ctid not in (select max(ctid) from test1 group by c1,c2);
QUERY
PLAN
---------------------------------------------------------------------------------------------------------------------------------------------
Seq Scan on public.test1 (cost=222.97..90895.39 rows=5085 width=8) (actual
time=54.451..7741.146 rows=51 loops=1)
Output: test1.c1, test1.c2
Filter: (NOT (SubPlan 1))
Rows Removed by Filter: 9949
Buffers: shared hit=90
SubPlan 1

发生了LOOP

-> Materialize (cost=222.97..238.23 rows=1017 width=14) (actual
time=0.001..0.297 rows=5000 loops=10000)
Output: (max(test1_1.ctid)), test1_1.c1, test1_1.c2
Buffers: shared hit=45
-> HashAggregate (cost=222.97..233.14 rows=1017 width=14)
(actual time=4.757..6.655 rows=9949 loops=1)
Output: max(test1_1.ctid), test1_1.c1, test1_1.c2
Group Key: test1_1.c1, test1_1.c2
Buffers: shared hit=45
-> Seq Scan on public.test1 test1_1 (cost=0.00..146.70
rows=10170 width=14) (actual time=0.005..1.588 rows=10000 loops=1)
Output: test1_1.c1, test1_1.c2, test1_1.ctid
Buffers: shared hit=45
Planning time: 0.121 ms
Execution time: 7741.277 ms
(18 rows)
```

when i use another user defined column , there is no LOOP.

test case

```
drop table test1;
create table test1(id int, c1 int, c2 int);
insert into test1 select id, random()*1000, random()*1000 from
generate_series(1,10000) t(id);

postgres=# explain (analyze,verbose,timing,costs,buffers) select * from
test1 where id not in (select max(id) from test1 group by c1,c2);
QUERY PLAN

---------------------------------------------------------------------------------------------------------------------------------------------
Seq Scan on public.test1 (cost=1048.18..1243.43 rows=5610 width=12)
(actual time=11.762..13.627 rows=48 loops=1)
Output: test1.id, test1.c1, test1.c2
Filter: (NOT (hashed SubPlan 1))
Rows Removed by Filter: 9952
Buffers: shared hit=110
SubPlan 1
-> GroupAggregate (cost=921.96..1045.38 rows=1122 width=12) (actual
time=5.355..9.162 rows=9952 loops=1)
Output: max(test1_1.id), test1_1.c1, test1_1.c2
Group Key: test1_1.c1, test1_1.c2
Buffers: shared hit=55
-> Sort (cost=921.96..950.01 rows=11220 width=12) (actual
time=5.350..6.101 rows=10000 loops=1)
Output: test1_1.c1, test1_1.c2, test1_1.id
Sort Key: test1_1.c1, test1_1.c2
Sort Method: quicksort Memory: 853kB
Buffers: shared hit=55
-> Seq Scan on public.test1 test1_1 (cost=0.00..167.20
rows=11220 width=12) (actual time=0.004..1.528 rows=10000 loops=1)
Output: test1_1.c1, test1_1.c2, test1_1.id
Buffers: shared hit=55
Planning time: 58.784 ms
Execution time: 13.685 ms
(20 rows)
```