How to Delete Firebase Data Older Than Two Hours?

Delete Firebase Data Older Than 2 Hours

The Question:

To avoid latency and optimize database performance, it's important to efficiently delete outdated data. This question seeks a way to remove Firebase data that is over two hours old.

The Solution:

Firebase does not allow querying with dynamic parameters like "two hours ago." Instead, we can execute a query for a specific timestamp, such as "after a specific past date and time."

To delete old data, consider the following code snippet:

var ref = firebase.database().ref('/path/to/items/');
var now = Date.now();
var cutoff = now - 2 * 60 * 60 * 1000;
var old = ref.orderByChild('timestamp').endAt(cutoff).limitToLast(1);
var listener = old.on('child_added', function(snapshot) {
    snapshot.ref.remove();
});

Here's how it works:

• Use child_added instead of value.
• Set limitToLast(1) to ensure only the last item after the cutoff is deleted.
• As items are deleted, Firebase triggers child_added for the next "last" item until all outdated items are removed.

For Cloud Functions for Firebase:

exports.deleteOldItems = functions.database.ref('/path/to/items/{pushId}')
.onWrite((change, context) => {
  var ref = change.after.ref.parent;
  var now = Date.now();
  var cutoff = now - 2 * 60 * 60 * 1000;
  var oldItemsQuery = ref.orderByChild('timestamp').endAt(cutoff);
  return oldItemsQuery.once('value', function(snapshot) {
    var updates = {};
    snapshot.forEach(function(child) {
      updates[child.key] = null
    });
    return ref.update(updates);
  });
});

This function executes whenever data is modified under /path/to/items, deleting child nodes only when they are being modified.

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