Join fix issue

gistfile1.sql

create table size_m as select i as id, repeat(i::text, i % 100) as val from generate_series(1, 20000) i;

create table size_l as select i as id, m.id as m_id, repeat(i::text, i % 100) as val from generate_series(1, 1000000) i, size_m m where i.i / 10 = m.id;

--create index idx_m_id on size_l (m_id);

analyze size_m;
analyze size_l;

----
select m_id, sum_len from size_m m inner join(select m_id, sum(length(val)) as sum_len from size_l group by m_id)l on m.id = l.m_id where val = '10101';