How can I design a Firestore schema to sort friend relationships by username?

One common approach is to duplicate the friend’s display name in each relationship document so that each document has an easily sortable field from the perspective of the querying user.

Why We Need a New Field

Right now your document stores both usernames (for example, as name1 and name2). However, when fetching a relationship document you don’t know ahead of time whether the current user is represented in name1 or name2. This uncertainty makes it impossible to sort by a single field without additional logic.

The Proposed Schema Change

When creating a relationship, add a new field (for example, friendName) that always stores the display name of the friend—that is, the user who is not the current user. For instance, if a user with UID "A" is querying for friends, each document would include the display name of the other friend (the one that is not "A") in the friendName field.

Sample Document Structure

{
  uids: ["A", "B"],
  compositeKey: "A_B",  // always sorted alphabetically
  initiator: "A",
  status: "friends",
  name1: "Alice",
  name2: "Bob",
  friendName: "Bob"    // from the perspective of user A, when A is querying
}

When the friend with UID "B" creates or sees the same relationship document, you can either store a separate field (like friendNameB) or duplicate the relationship document with the correct perspective; however, typically you’ll store the data once and then derive the required ordering either by duplicating the field for both users or by creating a direction‑specific field.

Querying with orderBy

Using the new sorted field, you can query as follows:

JAVASCRIPTCopied
firestore.collection("relationships")
  .whereArrayContains("uids", myUID)
  .whereEqualTo("status", "friends")
  .orderBy("friendName")
  .limit(10)
  .get()
  .then(snapshot => {
    // Process snapshot.docs here
  });

Summary

• Why the Change?
  Without knowing which username belongs to the friend, Firestore cannot sort correctly.
• What to Do?
  Augment your schema to store the friend’s display name in its own field.
• How to Query?
  Use orderBy on the new field so that pagination works properly with sorted data.

This schema change enables you to maintain pagination and server‑side sorting while using the orderBy function as needed.