JPA: Get visible elements in a tree relantionship in same table - spring-boot

Question

I have a hierarchical table of people in which I will have three levels:
Level 1: Grandfather: This always has the parent attribute to NULL
Level 2: Father: The parent attribute is Grandfather (Level 1)
Level 3: Child: The parent attribute is Father (Level 2)
The Postgres database table is as follows:
CREATE TABLE person(
cod_person varchar NOT NULL,
cod_parent varchar NULL,
visible bool NOT NULL,
CONSTRAINT s_person_pk PRIMARY KEY (cod_person)
);
And the JPA entity is as follows:
#Getter
#Entity
#EqualsAndHashCode(exclude = {"nodes"})
#NoArgsConstructor
#AllArgsConstructor
#Table(name = "person")
public class Person implements Serializable {
#Id
#Column(name = "cod_person")
private String id;
#ManyToOne(fetch = FetchType.LAZY)
#JoinColumn(name = "cod_parent")
private Person parent;
#OneToMany(mappedBy = "parent", fetch = FetchType.LAZY)
#Fetch(FetchMode.JOIN)
private Set<Person> childs = new HashSet<>();
#Column(name = "visible")
private Boolean isVisible;
}
Using JPA/JPQL (but never native query) and execute only one query I need to retrieve the visible elements. Based on these examples:
Case A:
cod_person
cod_parent
visible
1
null
true
2
1
true
3
2
true
4
2
true
5
1
true
6
5
true
7
5
true
In this case, I need retrieve this object:
Person 1:
parent: null
childs:
Person 2:
parent: Person 1
childs:
Person 3
Person 4
Person 5:
parent: Person 1
childs:
Person 6
Person 7
Case B:
cod_person
cod_parent
visible
1
null
true
2
1
true
3
2
true
4
2
true
5
1
true
6
5
false
7
5
false
In this case, I need retrieve this object:
Person 1:
parent: null
childs:
Person 2:
parent: Person 1
childs:
Person 3
Person 4
Person 5:
parent: Person 1
childs: EMPTY LIST
I have this query in JPQL:
#Repository
public interface PersonRepository extends JpaRepository<Person, String> {
#Query("SELECT DISTINCT granfather " +
"FROM Person granfather " +
"LEFT JOIN FETCH granfather.childs father " +
"LEFT JOIN FETCH father.childs child " +
"LEFT JOIN FETCH child.parent child_parent " + // To avoid new query to parent
"WHERE granfather.parent IS NULL " +
"AND granfather.isVisible = true " +
"AND father.isVisible = true " +
"AND child.isVisible = true ")
List<Person> findFamily();
}
With this query, case A works correctly, since all the Parents have children. The problem is in case B. When a Parent has no children, the query does not return this Parent and Person 5 is missing:
Person 1:
parent: null
childs:
Person 2:
parent: Person 1
childs:
Person 3
Person 4
I need to return this object since it is visible, with an empty child list.
How can I achieve this goal?