How to get only updated data Firebase

Question

I tried 2 ways.

First:

getUserReference()?.get()?.addOnSuccessListener {}

Second:

getUserReference()?.addListenerForSingleValueEvent(object : ValueEventListener {
    override fun onDataChange(snapshot: DataSnapshot) {}
    override fun onCancelled(error: DatabaseError) {}
})

But as I understand it, it returns all the data. Regardless of whether there was a data update or not. I want to upload data only if there have been changes on the server. How can this be done? Or I don't understand something.

score 2 · Answer 1 · answered Oct 06 '21 at 16:30

There is nothing built into Firebase for only getting updated data. If you want that, you will have to:

Add a timestamp to each child node, indicated when it was last updated.
Use a query to only get the updated data: ref.orderByChild("lastUpdated").startAt(System.currentTimeMillis())

This has been covered quite a few times before, so I recommend checking out the answers to some of these questions, including:

How to get only updated data Firebase

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