Adding fields in find() will produce extra SQL even LoadStrategy is JOINED

[michael-vascue]

Describe the bug
Adding fields in find() will produce extra SQL even LoadStrategy is JOINED.
Is it the expected behaviour?

Stack trace
N/A

To Reproduce
FYR: Initialise repo

constructor(
    @InjectRepository(User)
    private readonly userRepository: EntityRepository<User>,
}

Without fields will produce 1 query

await this.userRepository.find({}, {
      populate: ['roles'],
      strategy: LoadStrategy.JOINED,
      limit: 1,
});
/* Output:
select `e0`.`id`, `r1`.`id` as `r1__id`
from `user` as `e0` 
left join `user_roles` as `e2` on `e0`.`id` = `e2`.`user_id` 
left join `role` as `r1` on `e2`.`role_id` = `r1`.`id` limit 1
*/

With fields will produce 2 queries

await this.userRepository.find({}, {
      populate: ['roles'],
      fields: ['id', 'roles.id'], // id = users.id
      strategy: LoadStrategy.JOINED,
      limit: 1,
});
/* Output
select `e0`.`id` from `user` as `e0` limit 1 [took 5 ms]
select `e0`.`id`, `e1`.`role_id` as `fk__role_id` from `role` as `e0` left join `user_roles` as `e1` on `e0`.`id` = `e1`.`role_id` where `e1`.`user_id` in (7) limit 1 [took 6 ms]
*/

Expected behavior
Expected to produce 1 SQL whenever fields property is provided or not.

Additional context
N/A

Versions

Dependency	Version
node	14.15.0
typescript	4.2.4
mikro-orm	4.5.3
@mikro-orm/mysql	4.5.3
@mikro-orm/nestjs	4.2.0

[B4nan]

Yes, this combination is currently not implemented. Btw you can't use limit here if you want to use joined strategy and load to-many relation that way. You'd have to use QueryFlag.PAGINATE if you really need to restrict the SQL query limit, otherwise it will never select more than one entity at a level (so you would always end up with one role at most).

[michael-vascue]

Yes, this combination is currently not implemented. Btw you can't use limit here if you want to use joined strategy and load to-many relation that way. You'd have to use QueryFlag.PAGINATE if you really need to restrict the SQL query limit, otherwise it will never select more than one entity at a level (so you would always end up with one role at most).

Okay and Thanks for the recommendation.
BTW, MikroORM is great and we are using it to develop our product.