I'm not saying this is necessarily a bug since the whole function deals
with floats, but perhaps it's interesting to note that ndistinct can be
0 in src/backend/utils/adt/selfuncs.c:estimate_hash_bucketsize:
/*
* Initial estimate of bucketsize fraction is 1/nbuckets as long as the
* number of buckets is less than the expected number of distinct
values;
* otherwise it is 1/ndistinct.
*/
if (ndistinct > nbuckets)
estfract = 1.0 / nbuckets;
else
estfract = 1.0 / ndistinct;
for this query:
select subq_0.c1 as c0
from (
select ref_0.a as c0, (select NULL::integer from
information_schema.user_defined_types limit 1 offset 1) as c1
from public.rtest_nothn3 as ref_0
limit 130
) as subq_0
left join (
select sample_0.x as c0
from public.insert_tbl as sample_0
where false
) as subq_1 on subq_0.c1 = subq_1.c0;
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