How to create subcollection indexes at Cloud Firestore?

Question

I have googled and checked the Cloud Firestore documentation and found nothing about how to declare subcollections indexes. I have declared something like this

...{    
  "collectionId": "user/{uid}/feeds",
  "fields": [..]
}...

and in the indexes tab it is stored like this

__escuser~1{uid}~1feeds__

No idea if I created properly it or not.

Answer 1

When you go to create an index, it actually tells you to run the query you want to create an index for once manually and then it will generate a URL you can copy paste into the browser et voila!

This is how you do it:

1. Create a new dir
2. npm init
3. npm i --save firebase-admin
4. Create index.js

5. Put the following function in the document

   const admin = require('firebase-admin');
   const serviceAccount = require('./firebase-creds.json');
   
   admin.initializeApp({
     credential: admin.credential.cert(serviceAccount),
     databaseURL: 'https://projectId.firebaseio.com'
   });
   
   function runQuery() {
     db
     .collection('users')
     .doc(someRandomUserId)
     .collection('feed')
     .where('read', '==', false)
     .where('timestamp', '<=', 1509889854742) //Or something else
     .get()
     .then(doc => {
       console.log(doc.data());
     })
     .catch(error => console.log(error));
   };
   runQuery();
   

6. Run node index.js

This will spit someting like this out:

{ Error: The query requires an index. You can create it here: https://console.firebase.google.com/project/project-projectID/database/firestore/indexes?create_index=longRandomString ...}

Copy the link and paste it into your browser.

Update

To add the index manually (via the CLI) you can do the following:

{
  "indexes": [
    {
      "collectionId": "feed",
      "fields": [
        { "fieldPath": "read", "mode": "ASCENDING" },
        { "fieldPath": "timestamp", "mode": "ASCENDING" },
        ...
      ]
    }
  ]
}

Or simply go in to the admin panel in your database and add the index for feeds there.

Answer 2

This appears to be answered by @michael-bleigh here: https://stackoverflow.com/a/47165007/2511985

Cloud Firestore indexes are based on collection names, not full collection paths. So if you want to create indexes on users/{id}/messages, the correct way to do this is to create an index on messages.