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A very good W3school tutorial can be found here.

Javascript – Delete nodes in firebase realtime database based on nested values with random keys

I have a realtime database with following structure:

"keys" :
   "randomUserId1" :
       "randomKey1" : timestamp1
   "randomUserId2" :
       "randomKey2" : timestamp2
       "randomKey3" : timestamp3
   "randomUserId3" :
       "randomKey4" : timestamp4

The timestamp values are createdtime in milliseconds. I now want to delete all keys where timestamp is too old, using Firebase function and javascript. Timing is not that important, so the delete function may trigger on a suitable write somewhere else in the database.

I have tried modifying the example method delete old child nodes, but cannot understand how to make it work with above database structure.

How could I write a js function to accomplish above?

I could of course add a key/value pair ("timestamp" : timestamp) below "randomKey", if that makes things easier.

Tags:

2

Answers


  1. 0

    Firebase function (and using firebase-sdk) that deletes keys with timestamps that are older than a threshold value:

    const functions = require('firebase-functions');
const admin = require('firebase-admin');
admin.initializeApp();

exports.deleteOldKeys = functions.database.ref('/keys/{userId}/{key}')
  .onWrite(async (change, context) => {
    const timestampThreshold = Date.now() - (24 * 60 * 60 * 1000); // Change this to adjust the threshold
    const userId = context.params.userId;
    const key = context.params.key;
    if (!change.after.exists()) {
      // deleted key, no need to check timestamp
      return null;
    }
    const timestamp = change.after.val();
    if (timestamp < timestampThreshold) {
      // delete the key
      await admin.database().ref(`/keys/${userId}/${key}`).remove();
    }
    return null;
  });

    Source Reference/Inspiration

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  2. 0

    The link you provide is based on my answer to Delete firebase data older than 2 hours

    To make it work on your data structure, you can use orderByValue() rather than orderByChild("timestamp"). So:

    var oldItemsQuery = ref.orderByValue().endAt(cutoff);

    To learn more about this, see the Firebase documentation on sorting and filtering data.

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