How to listen to the first of ToMany

[TinoGuo]

@Entity
class Session {
    @Id
    var id: Long = 0
    
    lateinit var messages: ToMany<Message>
}

In my app, there is a session list, we need to listen to the first of messages, but now I can't find any direct method to listen.

My question: Is there any simple workaround to listen? BTW, now I need to add a extra field latestContent to solve this problem. Just as below.

@Entity
class Session {
    @Id
    var id: Long = 0

    //when update messages, update this field
    lateinit var latestContent: String
    
    lateinit var messages: ToMany<Message>
}

[greenrobot-team]

You can subscribe to a query for your Session entity. Your code will get a new set or results (in this case one) each time the entity is modified then.

Does that work for you? -ut

[TinoGuo]

If the messages were very big amount of items for example 100,000 , will it be very slow? Thanks.

[greenrobot-team]

By default ToMany is loaded on access. But to get the first item you probably will do that. If there are many items then yes, it may be slow and require a lot of memory. Improvements may be part of #510.

Another approach might be to change your model and try subscribing to a query on the Message box instead. However, until #303 it is not possible to set a limit when subscribing to a Query. -ut

[TinoGuo]

@greenrobot-team For my situation, I need to subscribe the last message that means insert will change the message entity. I can't get benifit from the two approach.

BTW, any feature #510 or #303 will come in next release?