Firebase Firestore add data without overwrite

Question

I am trying to add data to my firestore database. The firestore is this:

Firestore db

I have my php file that loads data into it with this code db.collection('events').doc('documentNameUsingUniqueEventID').set({id1:data1, id2:data2, id3:data3, ...});

but when I load new data and old still exists the documents gets overwrite and I lose the changes I made. Is there a way to add data avoiding overwrite existing ones?

Answer 1

The set() method on DocumentReference has a second parameter for SetOptions that allows you to say that you want to merge data into an existing document rather than overwrite it:

db.collection('events')
    .doc('documentNameUsingUniqueEventID')
    .set(data, { merge: true });