问为什么PostgreSQL递归查询迭代不返回与手工创建的结果相同的结果？

EN

SELECT * FROM attempts order by id;

 id | user_id | name
----+---------+------
  1 |       1 | a
  2 |       2 | b
  3 |       1 | b
  4 |       1 | c
  5 |       2 | a
  6 |       1 | a
  7 |       1 | b
  8 |       1 | a
  9 |       3 | c
 10 |       4 | d
 11 |       3 | d
(11 rows)

WITH RECURSIVE t(iter_id, id, user_id, name, aname, iname) AS (
  select 1, min(id) - 1, user_id, null, null, null as name from attempts group by user_id
UNION ALL
  select * from (
    with iter as (select * from t),
    t_min as (select min(id) as id from iter),
    next_id as (
      select min(attempts.id) as id
      from attempts
      left join iter using(name)
      where attempts.id > (select id from t_min)
      and iter.name is null
    )
    select iter.iter_id + 1, next_id.id, iter.user_id, coalesce(attempts.name, iter.name) as name, attempts.name aname, iter.name as iname
    from iter cross join next_id left join attempts
    on (attempts.id = next_id.id)
    and (attempts.user_id = iter.user_id)
    where next_id.id is not null
  ) as t2
)
select *
from t
order by iter_id, user_id, id
;

 iter_id | id | user_id | name | aname | iname
---------+----+---------+------+-------+-------
       1 |  0 |       1 | NULL | NULL  | NULL
       1 |  1 |       2 | NULL | NULL  | NULL
       1 |  8 |       3 | NULL | NULL  | NULL
       1 |  9 |       4 | NULL | NULL  | NULL
       2 |  1 |       1 | a    | a     | NULL
       2 |  1 |       2 | NULL | NULL  | NULL
       2 |  1 |       3 | NULL | NULL  | NULL
       2 |  1 |       4 | NULL | NULL  | NULL
       3 |  2 |       1 | a    | NULL  | a
       3 |  2 |       2 | b    | b     | NULL
       3 |  2 |       3 | NULL | NULL  | NULL
       3 |  2 |       4 | NULL | NULL  | NULL
       4 |  4 |       1 | c    | c     | a
       4 |  4 |       2 | b    | NULL  | b
       4 |  4 |       3 | NULL | NULL  | NULL
       4 |  4 |       4 | NULL | NULL  | NULL
       5 |  5 |       1 | c    | NULL  | c
       5 |  5 |       2 | a    | a     | b
       5 |  5 |       3 | NULL | NULL  | NULL
       5 |  5 |       4 | NULL | NULL  | NULL
       6 |  7 |       1 | b    | b     | c
       6 |  7 |       2 | a    | NULL  | a
       6 |  7 |       3 | NULL | NULL  | NULL
       6 |  7 |       4 | NULL | NULL  | NULL
       7 |  9 |       1 | b    | NULL  | b
       7 |  9 |       2 | a    | NULL  | a
       7 |  9 |       3 | c    | c     | NULL
       7 |  9 |       4 | NULL | NULL  | NULL
       8 | 10 |       1 | b    | NULL  | b
       8 | 10 |       2 | a    | NULL  | a
       8 | 10 |       3 | c    | NULL  | c
       8 | 10 |       4 | d    | d     | NULL
(32 rows)

select * from tmp;

 id | user_id | name
----+---------+------
  5 |       1 | c
  5 |       2 | b
  5 |       3 | NULL
  5 |       4 | NULL
(4 rows)

with iter as (select * from tmp),
t_min as (select min(id) as id from iter),
next_id as (
  select min(attempts.id) as id
  from attempts
  left join iter using(name)
  where attempts.id > (select id from t_min)
  and iter.name is null
)
select next_id.id, iter.user_id, coalesce(attempts.name, iter.name) as name, attempts.name aname, iter.name as iname
from iter cross join next_id left join attempts
on (attempts.id = next_id.id)
and (attempts.user_id = iter.user_id)
where next_id.id is not null
;

 id | user_id | name | aname | iname
----+---------+------+-------+-------
  6 |       1 | a    | a     | c
  6 |       2 | b    | NULL  | b
  6 |       3 | NULL | NULL  | NULL
  6 |       4 | NULL | NULL  | NULL
(4 rows)