Realm Delete Orphaned Objects in an Efficient Way

Question

I have a class BeaconBase containing list of BeaconData.

public class BeaconBase extends RealmObject {

    @PrimaryKey
    private Integer checkInID;

    @SerializedName("beacons")
    @Expose
    private RealmList<BeaconData> beacons;
}

public class BeaconData extends RealmObject {

    @SerializedName("scanId")
    @Expose
    private String scanId;

    @SerializedName("distance")
    @Expose
    private String distance;

}

BeaconData will usually be huge. May be around 100000 rows per hour. How do i efficiently delete BeaconData when i delete related BeaconBase record?

I have Primary Key only in BeaconBase.

So when i delete BeaconBase record, thousands of BeaconData records are being orphaned. How can i efficiently handle this situation?

Answer 1

try(Realm r = Realm.getDefaultInstance)) {
    r.executeTransaction((realm) -> {
        RealmResults<BeaconBase> beaconsToDelete = realm.where(BeaconBase.class)./*query here*/.findAll();
        for(int i = beaconsToDelete.size() - 1; i >= 0; i--) {
            BeaconBase beaconBase = beaconsToDelete.get(i);
            beaconBase.getBeacons().deleteAllFromRealm();
            beaconBase.deleteFromRealm();
        }
    });
}

Although to be slightly more of use, you could also do this:

public class BeaconBase extends RealmObject {

    @PrimaryKey
    private Integer checkInID;

    @SerializedName("beacons")
    @Expose
    private RealmList<BeaconData> beacons;
}

public class BeaconData extends RealmObject {

    @SerializedName("scanId")
    @Expose
    private String scanId;

    @SerializedName("distance")
    @Expose
    private String distance;

    @LinkingObjects("beacons")
    private final RealmResults<BeaconBase> beaconDataOf = null;
}

try(Realm r = Realm.getDefaultInstance)) {
    r.executeTransaction((realm) -> {
        realm.where(BeaconBase.class)./*query here*/.findAll().deleteAllFromRealm();
        realm.where(BeaconData.class).isEmpty("beaconDataOf").findAll().deleteAllFromRealm();
    });
}