How Can I Retrieve Subcollection Names in Cloud Firestore?

Finding Subcollection Names in Cloud Firestore

In Cloud Firestore, you'll often organize your data into a hierarchy with documents and subcollections. Retrieving subcollection names is essential for navigating this data structure.

Issue:

Retrieving subcollection names from within a document might seem intuitive, but it's not possible in mobile and web client SDKs. When you fetch a document with get(), it only returns the field values, not any nested collection names.

Reason:

Firestore's client SDKs prioritize security and performance. Exposing subcollection names could introduce potential vulnerabilities and impact performance.

Solution for Server-Side SDKs:

In Node.js and other server-side SDKs, you can access subcollection names using the Collection.listCollectionIds() method. This method provides a secure and performant way to retrieve subcollection names within a document.

Example:

const firestore = require('firestore.v1beta1');

const client = firestore.v1beta1({
  // optional auth parameters.
});

const formattedParent = client.anyPathPath("PROJECT", "DATABASE", "DOCUMENT", "ANY_PATH");

client.listCollectionIds({parent: formattedParent}).then((responses) => {
    const resources = responses[0];
    for (var i = 0; i < resources.length; ++i) {
        // doThingsWith(resources[i])
    }
})
.catch((err) => {
    console.error(err);
});

This solution provides a secure and efficient way to retrieve subcollection names in server-side environments. For mobile and web clients, you may need to consider alternative data structures or carefully manage subcollection names.

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