[sqlsmith] Failed assertion in parallel worker in ExecInitSubPlan

Hi,

the query below triggers a parallel worker assertion for me when run on
the regression database of master as of 0832f2d.  The plan sports a
couple of InitPlan nodes below Gather.

regards,
Andreas
Gather  (cost=1.64..84.29 rows=128 width=4)  Workers Planned: 1  Single Copy: true  ->  Limit  (cost=1.64..84.29
rows=128width=4)        ->  Subquery Scan on subq_0  (cost=1.64..451.06 rows=696 width=4)              Filter:
(subq_0.c6IS NOT NULL)              ->  Nested Loop Left Join  (cost=1.64..444.07 rows=699 width=145)
Join Filter: (sample_0.aa = sample_1.pageno)                    InitPlan 4 (returns $3)                      ->  Result
(cost=1.21..5.36 rows=15 width=0)                            One-Time Filter: ($0 AND ($1 = $2))
   InitPlan 1 (returns $0)                              ->  Result  (cost=0.00..0.00 rows=0 width=0)
               One-Time Filter: false                            InitPlan 2 (returns $1)
-> Limit  (cost=0.35..0.52 rows=1 width=4)                                    ->  Gather  (cost=0.00..1.04 rows=6
width=4)                                         Workers Planned: 1                                          ->
ParallelSeq Scan on reltime_tbl  (cost=0.00..1.04 rows=4 width=4)                            InitPlan 3 (returns $2)
                         ->  Limit  (cost=0.52..0.69 rows=1 width=4)                                    ->  Gather
(cost=0.00..1.04rows=6 width=4)                                          Workers Planned: 1
            ->  Parallel Seq Scan on reltime_tbl reltime_tbl_1  (cost=0.00..1.04 rows=4 width=4)
   ->  Sample Scan on pg_foreign_data_wrapper sample_2  (cost=1.21..5.36 rows=15 width=0)
  Sampling: system ('3.1'::real)                    ->  Nested Loop  (cost=0.15..382.85 rows=699 width=4)
          ->  Sample Scan on pg_largeobject sample_1  (cost=0.00..209.03 rows=699 width=8)
 Sampling: bernoulli ('2.9'::real)                                Filter: (pageno IS NOT NULL)
-> Index Only Scan using pg_foreign_table_relid_index on pg_foreign_table ref_0  (cost=0.15..0.24 rows=1 width=4)
                        Index Cond: (ftrelid = sample_1.loid)                    ->  Materialize  (cost=0.00..16.06
rows=4width=4)                          ->  Append  (cost=0.00..16.04 rows=4 width=4)                                ->
Sample Scan on a sample_0  (cost=0.00..4.01 rows=1 width=4)                                      Sampling: system
('5'::real)                               ->  Sample Scan on b sample_0_1  (cost=0.00..4.01 rows=1 width=4)
                        Sampling: system ('5'::real)                                ->  Sample Scan on c sample_0_2
(cost=0.00..4.01rows=1 width=4)                                      Sampling: system ('5'::real)
        ->  Sample Scan on d sample_0_3  (cost=0.00..4.01 rows=1 width=4)
Sampling:system ('5'::real)
 


--8<---------------cut here---------------start------------->8---
set force_parallel_mode to on;
set max_parallel_workers_per_gather to 2;

select 91 as c0
from (select       (select pfname from public.pslot limit 1 offset 3)          as c0,       ref_1.grandtot as c1,
(selectpg_catalog.min(procost) from pg_catalog.pg_proc)          as c2,       ref_0.ftoptions as c3,
ref_1.grandtotas c4,       sample_1.loid as c5,       pg_catalog.pg_rotate_logfile() as c6,       (select random from
public.hash_i4_heaplimit 1 offset 5)          as c7,       sample_1.loid as c8     from       public.a as sample_0
tablesamplesystem (5)           right join pg_catalog.pg_largeobject as sample_1 tablesample bernoulli (2.9)
inner join pg_catalog.pg_foreign_table as ref_0             on (sample_1.loid = ref_0.ftrelid )           on
(sample_0.aa= sample_1.pageno )         left join public.mvtest_tvv as ref_1         on (EXISTS (             select
            sample_2.fdwoptions as c0,                 sample_2.fdwhandler as c1,                 (select during from
public.test_range_excllimit 1 offset 89)                    as c2               from
pg_catalog.pg_foreign_data_wrapperas sample_2 tablesample system (3.1)               where (EXISTS (
select                      sample_3.b as c0,                       (select grantee from
information_schema.udt_privilegeslimit 1 offset 4)                          as c1,                       sample_3.b as
c2,                      sample_3.rf_a as c3,                       sample_3.b as c4,
sample_3.rf_aas c5,                       sample_3.rf_a as c6                     from
public.clstr_tst_sas sample_3 tablesample system (8.1)                     where sample_3.rf_a >= cast(null as int8)
                limit 141))                 and ((select f1 from public.reltime_tbl limit 1 offset 2)
  = (select f1 from public.reltime_tbl limit 1 offset 3)                     )               limit 49))     where
sample_1.pagenois not NULL) as subq_0
 
where subq_0.c6 is not NULL
limit 128;
--8<---------------cut here---------------end--------------->8---