Being new to Google Cloud Datastore I would like to make sure that I am on a right track.
What I need:
- many-to-many relationship
- the relationship itself has to hold data describing the relation
- strong consistency is required both ways:
- from user entity to all the data entities that this user has permissions to
- from data entity to all the users that have permission to it
This is what I came up with:
@Entity
public class User {
@Id String userId;
}
@Entity
public class PermissionIndex {
@Id long id;
@Parent Key<User> user;
List<Ref<Permission>> permissions;
}
@Entity
public class Permission {
@Id long id;
boolean writePermission;
boolean managePermission;
@Load Ref<Data> data; //So that Data entities can be retrieved with strong
//consistency after looking up Permission entities
//for a specific User entity
@Load Ref<User> user; //So that User entities can be retrieved with strong
//consistency after looking up Permission entities
//for a specific Data entity
}
@Entity
public class DataIndex {
@Id long id;
@Parent Key<Data> data;
List<Ref<Permission>> permissions;
}
@Enti.
public class Data {
@Id String dataId;
@Id String actualData;
}
If I understand right with this implementation the only way to filter Data Entities of a specific user is to get all Permission entities and filter Data entities in memory, am I right?
Is there a better way to implement it still fulfilling the requirements?
UPDATE:
In my understanding this implementation will allow me to implement logic that will retrieve data assuring strong consistency (having user id - ancestor query to retrieve all Permission entities and then using get_by_key to retrieve the Data entities).
I am wondering if I should approach it in a different way - since I do not have a lot of expierience with datastore/objectify.
