lateral join with union all - Mailing list pgsql-general

select * from
(
    (select 2 as v )
    union all
    (select 3 as v)
) as q1
cross join lateral
(   (select * from
    ((select 4 as v) union all
    (select 5 as v)) as q3
    )
    union all
    (select q1.v)
) as  q2;

I thought q1 will be materialized as a constant set and will be equivalent as  select 2 union all select 3;

Then It will  have 8 (2 * 4) rows total. Then It will be like {2,3} cross join with {2,3,4,5}

But Here the actual result(return 6 rows) feels like two separate queries(A,B) then union together.

QueryA: (select 2 as v ) cross join lateral (.....)

QueryB: (select 3 as v ) cross join lateral (.....)

Query A 3 row + Query B 3 row. So the total is 6 rows.