How to order documents by timestamp automatically in firebase?

Question

I've created an app and I am using firebase as well but I want to order the documents by timestamp such that my documents will be ordered from recently added ones to older ones.

I wonder if there is a solution rather than using orderBy method because my project is very big.

please help me.

Note: I am devolping the app using flutter & dart.

Solution

Firebase Realtime Database always returns results in ascending order. There is no way to order descending order.

This means you have two common options:

1. Reverse the nodes on the client.
2. Store an inverted value in a property, and order on that.

If you want to retrieve a subset of the items, keep in mind that you can combine any of these approaches with limitToFirst() and limitToLast. For example, to get the 10 most recent messages, you could:

1. order on timestamp
2. get the last 10 items
3. reverse them client-side

Also see:

• How to get data from firebase in descending order of value?, which shows an example of storing an inverted score.
• Sorting in descending order in Firebase database, which shows someone using the limitToLast approach mentioned above.
• Display posts in descending posted order, which shows how to invert a date value. Please ignore the use of priorities, as you'd nowadays just store the inverted value in a regular property and use orderByChild().
• Many more links from this list.

Comments

[dfdfdsfsd]

I did as you have mentioned above and I've created a field called time and it is equal to DateTime.now() (Dart) but it orders according to the current time of the users so this makes a disturbance in my app especially in chats

[Frank van Puffelen]

That sounds like a new problem problem to me. But if you want to have a consistent timestamp that is not dependent on the client-side click, use ServerValue.timestamp. Read more about it in the documentation here: firebase.google.com/docs/database/android/…