[sqlsmith] Failed to generate plan on lateral subqueries

Hi,

I've added new grammar rules to sqlsmith and improved some older ones.
This was rewarded with a return of "failed to generate plan" errors.
The failing queries all contain a lateral subquery. The shortest of the
failing queries are below. They were run against the regression db of
master as of db07236.

regards,
Andreas

smith=# select msg, query from error where
(firstline(msg) ~~ 'ERROR: failed to build any%'
or firstline(msg) ~~ 'ERROR: could not devise a query plan%')
and t > now() - interval '1 day' order by length(query) asc limit 3;

ERROR: failed to build any 8-way joins
select
ref_96.foreign_table_schema as c0,
sample_87.is_supported as c1
from
information_schema.sql_packages as sample_87 tablesample system (0.2)
right join information_schema._pg_foreign_tables as ref_96
on (sample_87.feature_id = ref_96.foreign_table_catalog ),
lateral (select
sample_87.is_verified_by as c0,
ref_97.indexed_col as c1,
coalesce(sample_87.feature_id, ref_96.foreign_server_name) as c2,
4 as c3
from
public.comment_test as ref_97
where ref_97.id ~>~ ref_97.indexed_col
fetch first 73 rows only) as subq_33
where ref_96.foreign_table_name ~~ subq_33.c1

ERROR: could not devise a query plan for the given query
select
subq_43.c0 as c0
from
(select
ref_181.installed as c0
from
pg_catalog.pg_available_extension_versions as ref_181,
lateral (select
ref_181.name as c0,
ref_181.installed as c1
from
pg_catalog.pg_conversion as ref_182
where ref_182.conname ~~* ref_181.version
fetch first 98 rows only) as subq_42
where (subq_42.c0 is not NULL)
or (subq_42.c1 is NULL)) as subq_43
right join pg_catalog.pg_language as sample_177 tablesample system (2.8)
on (subq_43.c0 = sample_177.lanispl )
where sample_177.lanowner < sample_177.lanvalidator

ERROR: failed to build any 5-way joins
select
ref_239.id2 as c0,
40 as c1,
ref_239.id2 as c2,
ref_238.aa as c3
from
public.tt5 as sample_289 tablesample system (8.1)
inner join information_schema.element_types as ref_237
on (sample_289.x = ref_237.character_maximum_length )
left join public.b as ref_238
on (ref_237.character_maximum_length = ref_238.aa )
left join public.num_exp_mul as ref_239
on (ref_237.numeric_precision_radix = ref_239.id1 ),
lateral (select
sample_290.b as c0,
sample_289.y as c1,
ref_239.id2 as c2
from
public.rtest_t8 as sample_290 tablesample bernoulli (4.6)
where (sample_290.b > ref_238.bb)
and (sample_289.y > ref_239.expected)
fetch first 91 rows only) as subq_64
where (subq_64.c1 > sample_289.y)
and (sample_289.y = ref_239.expected)
fetch first 133 rows only