Should consider materializing the cheapest inner path in consider_parallel_nestloop()

Hi all,

I recently run benchmark[1] on master, but I found performance problem
as below:

explain analyze select
subq_0.c0 as c0,
subq_0.c1 as c1,
subq_0.c2 as c2
from
(select
ref_0.l_shipmode as c0,
sample_0.l_orderkey as c1,
sample_0.l_quantity as c2,
ref_0.l_orderkey as c3,
sample_0.l_shipmode as c5,
ref_0.l_shipinstruct as c6
from
public.lineitem as ref_0
left join public.lineitem as sample_0
on ((select p_partkey from public.part order by p_partkey limit 1)
is not NULL)
where sample_0.l_orderkey is NULL) as subq_0
where subq_0.c5 is NULL
limit 1;
QUERY PLAN

-----------------------------------------------------------------------------------------------------------------------------------------
Limit (cost=78.00..45267050.75 rows=1 width=27) (actual
time=299695.097..299695.099 rows=0 loops=1)
InitPlan 1 (returns $0)
-> Limit (cost=78.00..78.00 rows=1 width=8) (actual
time=0.651..0.652 rows=1 loops=1)
-> Sort (cost=78.00..83.00 rows=2000 width=8) (actual
time=0.650..0.651 rows=1 loops=1)
Sort Key: part.p_partkey
Sort Method: top-N heapsort Memory: 25kB
-> Seq Scan on part (cost=0.00..68.00 rows=2000 width=8)
(actual time=0.013..0.428 rows=2000 loops=1)
-> Nested Loop Left Join (cost=0.00..45266972.75 rows=1 width=27)
(actual time=299695.096..299695.096 rows=0 loops=1)
Join Filter: ($0 IS NOT NULL)
Filter: ((sample_0.l_orderkey IS NULL) AND (sample_0.l_shipmode IS
NULL))
Rows Removed by Filter: 3621030625
-> Seq Scan on lineitem ref_0 (cost=0.00..1969.75 rows=60175
width=11) (actual time=0.026..6.225 rows=60175 loops=1)
-> Materialize (cost=0.00..2270.62 rows=60175 width=27) (actual
time=0.000..2.554 rows=60175 loops=60175)
-> Seq Scan on lineitem sample_0 (cost=0.00..1969.75
rows=60175 width=27) (actual time=0.004..8.169 rows=60175 loops=1)
Planning Time: 0.172 ms
Execution Time: 299695.501 ms
(16 rows)

After I set enable_material to off, the same query run faster, as below:
set enable_material = off;
explain analyze select
subq_0.c0 as c0,
subq_0.c1 as c1,
subq_0.c2 as c2
from
(select
ref_0.l_shipmode as c0,
sample_0.l_orderkey as c1,
sample_0.l_quantity as c2,
ref_0.l_orderkey as c3,
sample_0.l_shipmode as c5,
ref_0.l_shipinstruct as c6
from
public.lineitem as ref_0
left join public.lineitem as sample_0
on ((select p_partkey from public.part order by p_partkey limit 1)
is not NULL)
where sample_0.l_orderkey is NULL) as subq_0
where subq_0.c5 is NULL
limit 1;
QUERY
PLAN
-----------------------------------------------------------------------------------------------------------------------------------------------
Limit (cost=1078.00..91026185.57 rows=1 width=27) (actual
time=192669.605..192670.425 rows=0 loops=1)
InitPlan 1 (returns $0)
-> Limit (cost=78.00..78.00 rows=1 width=8) (actual
time=0.662..0.663 rows=1 loops=1)
-> Sort (cost=78.00..83.00 rows=2000 width=8) (actual
time=0.661..0.662 rows=1 loops=1)
Sort Key: part.p_partkey
Sort Method: top-N heapsort Memory: 25kB
-> Seq Scan on part (cost=0.00..68.00 rows=2000 width=8)
(actual time=0.017..0.430 rows=2000 loops=1)
-> Gather (cost=1000.00..91026107.57 rows=1 width=27) (actual
time=192669.604..192670.422 rows=0 loops=1)
Workers Planned: 1
Params Evaluated: $0
Workers Launched: 1
-> Nested Loop Left Join (cost=0.00..91025107.47 rows=1
width=27) (actual time=192588.143..192588.144 rows=0 loops=2)
Join Filter: ($0 IS NOT NULL)
Filter: ((sample_0.l_orderkey IS NULL) AND
(sample_0.l_shipmode IS NULL))
Rows Removed by Filter: 1810515312
-> Parallel Seq Scan on lineitem ref_0 (cost=0.00..1721.97
rows=35397 width=11) (actual time=0.007..3.797 rows=30088 loops=2)
-> Seq Scan on lineitem sample_0 (cost=0.00..1969.75
rows=60175 width=27) (actual time=0.000..2.637 rows=60175 loops=60175)
Planning Time: 0.174 ms
Execution Time: 192670.458 ms
(19 rows)

I debug the code and find consider_parallel_nestloop() doesn't consider
materialized form of the cheapest inner path.
When enable_material = true, we can see Material path won in first plan,
but Parallel Seq Scan node doesn't add as outer path, which because
in try_partial_nestloop_path() , the cost of nestloop wat computed using
seq scan path not material path.

[1] include test table schema and data, you can repeat above problem.

I try fix this problem in attached patch, and I found pg12.12 also had this
issue. Please review my patch, thanks!

[1] https://github.com/tenderwg/tpch_test