How to List Subcollections in Cloud Firestore: Client vs. Server-Side Approaches?

How to list subcollections in a Cloud Firestore document

In Cloud Firestore, documents can have subcollections, which are essentially collections that are nested within a document. To retrieve the names of the subcollections within a document, there are different approaches depending on whether you're using a client-side or server-side SDK.

Client-side SDKs

In client-side SDKs (e.g., web, iOS, Android), getting a list of subcollection names is currently not supported. According to the Firestore documentation:

Retrieving a list of collections is not possible with the mobile/web client libraries. You should only look up collection names as part of administrative tasks in trusted server environments. If you find that you need this capability in the mobile/web client libraries, consider restructuring your data so that subcollection names are predictable.

Server-side SDKs

On the other hand, server-side SDKs provide methods to retrieve subcollection names. For example, in the Node.js SDK, you can use the listCollectionIds method:

const {Firestore} = require('@google-cloud/firestore');
const firestore = new Firestore();

const documentRef = firestore.doc('rootCollection/aDocument');

documentRef.listCollections().then((collections) => {
  const subcollectionNames = collections.map(collection => collection.id);
  console.log(subcollectionNames); // ['subCollection1', 'subCollection2']
});

Other options

If you need to retrieve subcollection names in a client-side environment, you could consider the following alternative approaches:

• Use a predictable naming convention: Define a consistent naming convention for your subcollections, making it easy to deduce the names based on the parent document.
• Maintain a metadata document: Create a separate document that stores the names of all subcollections within the document.

The above is the detailed content of How to List Subcollections in Cloud Firestore: Client vs. Server-Side Approaches?. For more information, please follow other related articles on the PHP Chinese website!