How Can I Retrieve Subcollection Names from a Cloud Firestore Document?

How to retrieve subcollection names from a Cloud Firestore document

Retrieving the names of subcollections from a document in Cloud Firestore is a common task when working with complex document structures. While it may seem like a straightforward operation, it's not currently supported in the client SDKs for web and mobile platforms.

The Limitation

As per the official documentation, retrieving subcollection names directly from the client SDKs is not feasible. The documentation explicitly states that this functionality should be reserved for trusted server environments where administrative tasks are performed.

Why This Limitation Exists

The primary reason for this limitation is security. Subcollection names can be sensitive information, and allowing direct access to them in the client SDKs could pose security risks.

Solution for Server-Side SDKs

If you need to list subcollections in a document using server-side SDKs, such as Node.js, you can utilize the ListCollectionIds method. Here's an example:

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

firestore.collection('rootCollection/aDocument/subCollection1').listCollections().then((collections) => {
  for (const collection of collections) {
    console.log(`Found subcollection: ${collection.id}`);
  }
});

Managing Subcollection Names Predictably

Since you cannot retrieve subcollection names directly in the client SDKs, it's essential to design your data structure accordingly. Consider using predictable naming conventions for your subcollections to ensure you can manage them effectively without the need for direct lookups.

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