[SQL] Using null values in em.find's FilterQuery leads to unexpected results

[darkbasic]

@Entity()
export class Message extends BaseIdEntity {
  @ManyToMany({pivotTable: 'message_to_deletion'})
  deletions: Collection<User> = new Collection<User>(this);

This is a query which matches a non-null value on the M:N deletions field:

em.find(Message, {
  group: groupId,
  deletions: 1,
});

This is the sql that gets generated:

select "e0".*, "e1"."message_id", "e1"."user_id"
from "message" as "e0"
left join "message_to_deletion" as "e1"
on "e0"."id" = "e1"."message_id"
where "e0"."group_id" = 1 and "e1"."user_id" = 1

So far so good.

Now let's try to match a null value instead:

em.find(Message, {
  group: groupId,
  deletions: null,
});

This is what gets generated:

select "e0".*, "e1"."message_id", "e1"."user_id"
from "message" as "e0"
left join "message_to_deletion" as "e1"
on "e0"."id" = "e1"."message_id"
where "e0"."group_id" = 25 and "e0"."deletions" is null

This obviously won't work, because deletions is not a column.

Expected behavior

select "e0".*, "e1"."message_id", "e1"."user_id"
from "message" as "e0"
left join "message_to_deletion" as "e1"
on "e0"."id" = "e1"."message_id"
where "e0"."group_id" = 1 and "e1"."user_id" is null

Additional context

em.find(Message, {
  group: groupId,
  deletions: {id: null},
});

The previous workaround works, but with some caveats: in fact having to explicitly specify the PK column will trigger an unnecessary join, see #549

Versions

Dependency	Version
node	v13.14.0
typescript	3.8.3
mikro-orm	3.6.11
pg	8.0.3

[B4nan]

Closing as fixed in dev via fdc9e06