JOIN with no results produces entity with nulled properties

Issue type:

[x] question [ ] bug report [ ] feature request [ ] documentation issue

Database system/driver:

[ ] cordova [ ] mongodb [ ] mssql [ ] mysql / mariadb [ ] oracle [x] postgres [ ] cockroachdb [ ] sqlite [ ] sqljs [ ] react-native [ ] expo

TypeORM version:

[x] latest [ ] @next [ ] 0.x.x (or put your version here)

First, thank you for providing this amazing ORM to the community. You guys are doing awesome work on this project.

Now, I have an issue with “custom” many-to-many that you hopefully can help me with.

I wanted to have a Many-to-many relationship setup using TypeORM, but I needed to add some extra properties to the pivot table between them and was therefore not able to use an “automatically” generated pivot table.

Instead, I ended up doing this:

@Entity()
export class User {

    ...other properties

    @OneToMany(type => Participant, participants => participants.user)
    events: Array<Participant>;

}

@Entity()
export class Participant {

    ...other properties

    @ManyToOne(type => CalendarEvent, calendarEvent => 
    calendarEvent.participants, { primary: true })
    event: CalendarEvent;

    @ManyToOne(type => User, user => user.events, { primary: true })
    user: User;

}

@Entity()
export class CalendarEvent {

    ...other properties

    @OneToMany(type => Participant, participants => participants.event)
    participants: Array<Participant>;

}

This works if I left JOIN from either CalendarEvent to pivot, or from User to pivot and will produce an empty array if there are no results. But if I left join once more to get the other entity as well, I get a pivot object back where all properties are null.

Joining once:

return this.entityManager.createQueryBuilder(User, "user")
                                .leftJoinAndSelect("user.events", "pivot")
                                .where("user.id = :ID", {
                                    ID: "UUID-in-here"
                                })
                                .getOne();

It produces empty arrays when there is no results:

{
    "id": "UUID-in-here"
    "events": []
}

Joining again to retreive the event data:

return this.entityManager.createQueryBuilder(User, "user")
                                .leftJoinAndSelect("user.events", "pivot")
                                .leftJoinAndSelect("pivot.event", "event")
                                .where("user.id = :ID", {
                                    ID: "UUID-in-here"
                                })
                                .getOne();

I get the following result:

{
    "id": "UUID-in-here"
    "events": [
        {
            ...extra pivot columns here with value = null
            "event": null
        }
    ]
}

This doesn’t happen if you left JOIN multiple times using “normal” many-to-many relationships. For instance, if I run this:

return this.entityManager.createQueryBuilder(User, "user")
                            .leftJoinAndSelect("user.teams", "team")
                            .leftJoinAndSelect("team.messages", "message")
                            .where("user.id = :ID", {
                                ID: "UUID-in-here"
                            })
                            .getOne();

Where user is many-to-many with teams, and team is many-to-many with messages, I get empty arrays if there is no relationship.

Either:

{
    "id": "UUID-in-here",
    "teams": []
}

or:

{
    "id": "UUID-in-here",
    "teams": [
        "id": "UUID-in-here",
        "messages": []
    ]
}

How do I setup the relationship/query to avoid having that object with nulled properties when there are no results?

[CarstenWalther]

I stumbled across the same problem yesterday. It has something to do with the composed primary key over two relations (over event and user in the example above). If there is a separate primary id column instead, the result does not contain the object with null properties.

[MardariG]

Omg, this issue is from before COVID era. Any milestone?