I'm using Firestore to store messages. In order to optimize the mobile application performances, I would like to set a limit(50) in the firestore query.
It works well and implemented the onLoadEarlier React-native-gifted-chat available in the props.

All is working fine.

But, when I send a new message in the chat, after scrolled up to see the earliers messages, only the 50 last messages with the new one, off course, are available.

So, each time I'm adding a message in the Firestore database, the onSnapshot (in the useeffect) is executed and apply the limit query.

Is there a way to avoid this ?

Thanks.

Here my useEffect :

```
useEffect(() => {
    const messagesListener = firestore()
    .collection('groups')
    .doc(group._id)
    .collection('messages')
    .orderBy('createdAt', 'desc')
    .limit(50)
    .onSnapshot(querySnapshot => {
        const newMessages = querySnapshot.docs.map(doc => {
            const firebaseData = doc.data();

            const data = {
                _id: doc.id,
                text: '',
                createdAt: new Date().getTime(),
                ...firebaseData
            };

            return data;
        });

        setMessages(previousMessages => {
            return GiftedChat.append(previousMessages, newMessages);
        });
    });

    return () => messagesListener();
}, []);

```