How to query normalized firestore database

Question

I have a Firestore Database that looks like this:

Root
    Accounts
            username: UID1
    Friends
            id: SOME_ID
            members: {UID1, UID2}

I display all the friends in a RecyclerView. But how can I use the username field in the Accounts collection to query the Friends List?

score 1 · Accepted Answer · answered Nov 20 '21 at 15:23

With your current data model you'll have to load each friend's user profile separately based on their UID to get their username.

Alternatively you can change your data model to also include the user name for each member in the Friends document already. While this data duplication may seem unnatural if you come from a background in relational databases, it is really common in NoSQL databases - and one of the reasons they scale so well when reading data.

To learn more about this, also check out:

This article on NoSQL data modeling
Todd's excellent video series: Getting to know Cloud Firestore
My answer on How to write denormalized data in Firebase. While written for Realtime Database, it applies equally to Firestore.

score 0 · Answer 2 · answered Feb 24 '22 at 05:11

app.get("/player/:id", async (req, res) => {
  
  let { id: playerId } = req.params;
  if (!playerId) {
    res.status(400).send({
      success: false,
      message: "Kindly provide player ID",
    });
    return 0;
  }
  try {
    const snapshot = await admin
      .firestore()
      .collection("players")// players root user
      .doc(playerId)  //  sub folder   
      .get();
    let userData = snapshot.data();
    if (userData) {
      res.status(200).send({ ...userData });
      return 0;
    } else {
      res.status(400).send({
        success: false,
        message: "player does not exists in database",
      });
    }
  } catch (err) {
    res.status(400).send({ success: false, message: err.message });
  }
});

How to query normalized firestore database

2 Answers2