Add Firestore Vector Search to your mobile apps with Firebase Extensions

1. Overview

In this codelab, you will learn how to add powerful search features to your app using Firestore vector similarity search. You will implement a semantic search feature for a note-taking app written in Swift and SwiftUI.

Cloud Firestore console showing some documents, which also are visible in the iOS app on the right hand side.

What you will learn

  • How to install the Vector Search with Firestore extension to compute vector embeddings.
  • How to call Firebase Cloud Functions from a Swift application.
  • How to pre-filter data based on the signed-in user.

What you will need

  • Xcode 15.3
  • The codelab sample code. You will download this in a later step of the codelab.

2. Create and set up a Firebase project

To use the Firebase Vector Search extension, you need a Firebase project. In this part of the codelab, you will create a new Firebase project, and activate the required services such as Cloud Firestore and Firebase Authentication.

Create a Firebase project

  1. Sign in to Firebase
  2. In the Firebase console, click Add project, then name your project Firestore Vector Search LabCreate a project, step 1 of 3: choosing the project name
  3. Click through the project creation options. Accept the Firebase terms if prompted.
  4. On the Google Analytics screen, uncheck the Enable Google Analytics for this project box, because you won't be using Analytics for this app.
  5. Finally, click on Create project.

To learn more about Firebase projects, see Understand Firebase projects.

Enable and set up Firebase products in the console

The app that you're building uses several Firebase products that are available for Apple apps:

  • Firebase Authentication to easily allow your users to sign in to your app.
  • Cloud Firestore to save structured data on the cloud and get instant notification when data changes.
  • Firebase Security Rules to secure your database.

Some of these products need special configuration or need to be enabled using the Firebase console.

Enable anonymous authentication for Firebase Authentication

This application makes use of anonymous authentication to allow users to start using the app without first having to create an account. This results in a low-friction onboarding process. To learn more about anonymous authentication (and how to upgrade to a named account), see Best Practices for anonymous authentication.

  1. In the left-side panel of the Firebase console, click Build > Authentication. Then click Get started.Enabling Firebase Autentication
  2. You're now in the Authentication dashboard, where you can see signed-up users, configure sign-in providers, and manage settings.
  3. Select the Sign-in method tab (or click here to go directly to the tab).
  4. Click Anonymous from the provider options, toggle the switch to Enable, and then click Save.

Set up Cloud Firestore

This Swift application uses Cloud Firestore to save notes. Here is how to set up Cloud Firestore:

  1. In the left-side panel of the Firebase console, click Build > Firestore Database. Then click Create database.Enabling Cloud Firestore
  2. Select the location for your database, making sure you pick a location where Gemini is available (you can just use us-central1). Note, though, that this location can't be changed later. Click Next.
  3. Select the Start in test mode option. Read the disclaimer about the security rules. Test mode ensures that you can freely write to the database during development.Setting up Security Rules for Firestore in test mode
  4. Click Create to create the database.

3. Connect the mobile app

In this section of the codelab, you will download the source code for a simple note-taking app, and connect it to the Firebase project you just created.

Download the sample app

  1. Go to, and clone the repository to your local machine
  2. Open the Notes.xcodeproj project in Xcode

Connect the app to your Firebase project

For your app to be able to access Firebase services, you will need to set up the app in the Firebase console. You can connect multiple client applications to the same Firebase project, for example if you create an Android or web app, you should connect them to the same Firebase project.

To learn more about Firebase projects, see Understand Firebase projects.

  1. In the Firebase console, go to the overview page of your Firebase project.The overview page of the Firebase console
  2. Click on the iOS+ icon to add your iOS app.
  3. In the Add Firebase to your Apple app screen, insert the bundle ID from the Xcode project (
  4. If you like, you can enter an app nickname (Notes for iOS).
  5. Click on Register app to advance to the next step.
  6. Download the GoogleServices-Info.plist file.
  7. Drag GoogleServices-Info.plist into the Notes folder of your Xcode project. A good way to do this it to drop it beneath the Assets.xcassets file.Dragging the plist file into Xcode
  8. Select Copy items if needed, make sure that the Notes target is selected in Add to targets, and click on Finish.Selecting “Copy if needed” in the choose options for adding files dialog
  9. In the Firebase console, you can now click through the rest of the setup process: the sample you downloaded in the beginning of this section already has the Firebase Apple SDK installed, and the initialisation set up. You can finish the process by clicking Continue to console.

Run the app

It's now time to take the app for a spin!

  1. Back in Xcode, run the app on the iOS Simulator. In the Run Destinations drop-down, first select one of the iOS Simulators.Selecting an iOS Simulator in the Run Destinations drop-down
  2. Then, click the Run button, or press ⌘ + R
  3. Once the app has successfully launched on the Simulator, add a couple of notes.
  4. In the Firebase console, navigate to the Firestore data browser, so you can see new documents being created as you add new notes in the app.Cloud Firestore console showing some documents, alongside the iOS Simulator which shows the same documents

4. Install the Vector Search with Firestore extension

In this part of the codelab, you will install the Vector Search with Firestore extension, and configure it to the requirements of the note-taking app you're working on.

Initiate installing the extension

  1. Still in the Firestore section, click on the Extensions tab.Selecting the Firebase Extensions tab in the Firestore console
  2. Click on Explore Extensions Hub.Firebase Extensions tab in the Firestore console
  3. Type in "vector".
  4. Click on "Vector Search with Firestore extension".The Firebase Extensios Hub landing page This will take you to the extension's details page, where you can read more about the extension, how it works, which Firebase services it requires, and how you can configure it.
  5. Click on Install in Firebase console.The install button for the Vector Search with Firestore extension
  6. You will be presented with a list of all your projects.
  7. Pick the project you created in the first step of this codelab.The Firebase project selector screen

Configure the extension

Firebase Extensions make use of Cloud Functions for Firebase, which require your project to be on the pay-as-you-go Blaze plan. Before you can use the Vector Search with Firestore extension, you need to upgrade your project.

  1. Click on Upgrade project to continue. Upgrading the project to the Blaze plan
  2. Select an existing billing account, or create a new one. Click continue.Selecting a billing account
  3. Set a budget (e.g. 10 USD), click on Continue, then click on Purchase.Setting up a budget
  4. Review the APIs enabled and resources created.Reviewing the enabled APIs
  5. Enable the required services.Enabling the required services
  6. When enabling Cloud Storage, select test mode for the security rules.
  7. Confirm that Cloud Storage will use the same location as your Cloud Firestore instance.
  8. Once all services are enabled, click on Next.Click next after enabling all services
  9. Review access granted to this extension.
  10. Configure the extension:
    • Select Vertex AI as the LLM
    • Collection path: notes
    • Default query limit: 3
    • Input field name: text
    • Output field name: embedding
    • Status field name:* *status*
    • Embed existing documents: Yes
    • Update existing documents: Yes
    • Cloud Function location: us-central1
  11. Click on Install extension to finish the installation.

This might take a couple of minutes. While you're waiting for the installation to complete, feel free to advance to the next section of the tutorial and read some background information about vector embeddings.

5. Background

While you're waiting for the installation to finish, here's some background information about how the Vector Search with Firestore extension works.

What are Vectors, Embeddings, and Vector Databases?

  • Vectors are mathematical objects that represent the magnitude and direction of a quantity. They can be used to represent data in a way that makes it easier to compare and search.
  • Embeddings are vectors that represent the meaning of a word or phrase. They are created by training a neural network on a large corpus of text and learning the relationships between words.
  • Vector databases are databases that are optimized for storing and searching vector data. They allow for efficient nearest neighbor search, which is the process of finding the most similar vectors to a given query vector.

How does Vector Search work?

Vector search works by comparing the query vector to all of the vectors in the database. The vectors that are most similar to the query vector are returned as the search results.

The similarity between two vectors can be measured using a variety of distance metrics. The most common distance metric is the cosine similarity, which measures the angle between two vectors.

6. Try the Vector Search with Firestore extension

Before using the Vector Search with Firestore extension in the iOS app you downloaded earlier in this codelab, you can try out the extension in the Firebase console.

Read the documentation

Firebase Extensions include documentation on how they work.

  1. Once the extension has finished installing, click on the Get started button. The Firebase Extension overview page in the Firebase console
  2. Check out the "How this extension works" tab - it explains:
    • how to compute embeddings for documents by adding them to the notes collection,
    • how to query the index by calling the ext-firestore-vector-search-queryCallable callable function,
    • or how to query the index by adding a query document to the _firestore-vector-search/index/queries collection.
    • It also explains how to set up a custom embedding function - this is useful if none of the LLMs supported by the extension meets your requirements, and you would like to use a different LLM to compute embeddings. The documentation for the Vector Search with Firestore extension
  3. Click on the Cloud Firestore dashboard link to go to your Firestore instance
  4. Navigate to the _firestore-vector-search/index document. It should show that the extension has finished computing the embeddings for all of the notes documents you created in an earlier step in this codelab.The index configuration inside the Firestore console
  5. To verify this, open one of the notes documents, and you should see an additional field named embedding of type vector<768>, as well as a status field.A vector embedding field inside the Firestore console

Create a sample document

You can create a new document in the Firebase console to see the extension in action.

  1. Still in the Firestore data browser, navigate to the notes collection and click on + Add document in the middle column.Adding a new document
  2. Click Auto-ID to generate a new unique document ID.
  3. Add a field named text of type string, and paste some text into the value field. It's important that this is not lorem ipsum or some other random text. Pick a news article, for example.Adding a text field
  4. Click Save.
    • Notice how the extension adds a status field to indicate it is processing data.
    • After a short moment, you should see a new field embedding with a value of vector<768>.
    Vector embeddings status update for the new document

Perform a query

The Vector Search with Firestore extension has a nifty little feature that allows you to query the document index without having to connect an app.

  1. In the Firestore section of the Firebase console, go to the _firestore-vector-search/index document
  2. Click on + Start collectionAdding a new sub-collection
  3. Create a new sub-collection named queries
  4. Create a new document and set the query field to a text that occurs in one of your documents. This works best for semantic queries, like "How can I map Firestore documents with Swift" (provided at least one of the notes you added contains text that discusses this topic).Adding a query field
  5. You might see an error in the statusAn error occurred
  6. This is due to a missing index. To set up the missing index configuration, go to the Google Cloud console for your project by following this link, and then selecting your project from the listSelecting the correct project
  7. In the Cloud Log Explorer, you should now see an error message saying "FAILED_PRECONDITION: Missing vector index configuration. Please create the required index with following gcloud command: ..."Error message in the log explorer
  8. The error message also contains a gcloud command that you need to run to configure the missing index.
  9. Run the following command from your command line. If you don't have the gcloud CLI installed on your machine, follow the instructions here to install it.
    gcloud alpha firestore indexes composite create --project=INSERT-YOUR=PROJECT-ID-HERE --collection-group=notes --query-scope=COLLECTION --field-config=vector-config='{"dimension":"768","flat": "{}"}',field-path=embedding
    Creating the index takes a few minutes. You can check the progress on the Indexes tab in the Firestore section of the Firebase console.Status of the new index
  10. Once the index is set up, you can create a new query document.
  11. You should now see a list of matching document IDs in the results fieldResult of performing a semantic query
  12. Copy one of those IDs, and go back to the notes collection.
  13. Use ⌘+F to search for the document ID you copied - this document is the one that best matches your query.Finding the document ID in the list of documents

7. Implement semantic search

It's finally time to connect your mobile app to the Vector Search with Firestore extension and implement a semantic search feature that will allow your users to search their notes using natural language queries.

Connect the callable function for performing queries

The Vector Search with Firestore extension includes a Cloud Function that you can call from your mobile app to query the index you created earlier in this codelab. In this step, you will establish a connection between your mobile app and this callable function. Firebase's Swift SDK includes APIs that make calling remote functions seamless.

  1. Go back to Xcode, and make sure you're in the project you cloned in a previous step in this codelab.
  2. Open the NotesRepository.swift file.
  3. Find the line containing private lazy var vectorSearchQueryCallable: Callable = functions.httpsCallable("")

To invoke a callable Cloud Function, you need to provide the name of the function you want to call.

  1. Go to the Firebase console for your project, and open the Functions menu item in the Build section.
  2. You will see a list of functions that have been installed by the extension.
  3. Search for the one named ext-firestore-vector-search-queryCallable, and copy its name.
  4. Paste the name into your code. It should now read
    private lazy var vectorSearchQueryCallable: Callable<String, String> = functions.httpsCallable("ext-firestore-vector-search-queryCallable")

Call the query function

  1. Find the method performQuery
  2. Call your callable function by invoking
    let result = try await vectorSearchQueryCallable(searchTerm)

As this is a remote call, it might fail.

  1. Add some basic error handling to catch any errors and log them to Xcode's console.
    private func performQuery(searchTerm: String) async -> [String] {
      do {
        let result = try await vectorSearchQueryCallable(searchTerm)
        return [result]
      catch {
        return []

Connect the UI

To allow users to search their notes, you will implement a search bar in the notes list screen. When the user types in a search term, you need to invoke the performQuery method you implemented in the previous step. Thanks to the searchable and task view modifiers provided by SwiftUI, this only requires a couple of lines of code.

  1. First, open NotesListScreen.swift
  2. To add a search box to the list view, add the .searchable(text: $searchTerm, prompt: "Search") view modifier just above the line .navigationTitle("Notes")
  3. Then, invoke the search function by adding the following code just below:
.task(id: searchTerm, debounce: .milliseconds(800)) {
  await notesRepository.semanticSearch(searchTerm: searchTerm)

This code snippet calls your semanticSearch method asynchronously. By providing a timeout of 800 milliseconds, you instruct the task modifier to debounce the user's input by 0.8 seconds. This means that semanticSearch will only be called once the user pauses typing for more than 0.8 seconds.

Your code should now look like this:

List(repository.notes) { note in
  NavigationLink(value: note) {
    NoteRowView(note: note)
  .swipeActions {
    Button(role: .destructive, action: { deleteNote(note: note) }) {
      Label("Delete", systemImage: "trash")
.searchable(text: $searchTerm, prompt: "Search")
.task(id: searchTerm, debounce: .milliseconds(800)) {
  await notesRepository.semanticSearch(searchTerm: searchTerm)

Run the app

  1. Press ⌘ + R (or click on the Run button) to launch the app on the iOS Simulator
  2. You should see the same notes you added in the app earlier in this codelab, as well as any notes you added via the Firebase console
  3. You should see a search field at the top of the Notes list
  4. Type in a term that appears in one of the documents you added. Again, this works best for semantic queries, like "How can I call asynchronous Firebase APIs from Swift" (provided at least one of the notes you added contains text that discusses this topic).
  5. You probably expect to see the search result, but instead, the list view is empty, and the Xcode console displays an error message: "The function was called with an invalid argument"

The Notes app, with an empty results list

This means you sent the data in the wrong format.

Analyze the error message

  1. To find out what's wrong, go to the Firebase console
  2. Go to the Functions section
  3. Find the ext-firestore-vector-search-queryCallable function, open the overflow menu by clicking on the three vertical dots
  4. Select View logs to go to the logs explorer
  5. You should see an error
Unhandled error ZodError: [
    "code": "invalid_type",
    "expected": "object",
    "received": "string",
    "path": [],
    "message": "Expected object, received string"

This means you sent the data in the wrong format.

Use the correct data types

To find out which format the extension expects the parameters to be in, check out the extension's documentation.

  1. Go to the Extensions section on the Firebase console
  2. Click on Manage ->Managing the Vector Search with Firestore extension
  3. In the How this extension works section, you will find a specification of the input and output parameters.Documentation of the input parameter and result value
  4. Go back to Xcode, and navigate to NotesRepository.swift
  5. Add the following code at the beginning of the file:
    private struct QueryRequest: Codable {
      var query: String
      var limit: Int?
      var prefilters: [QueryFilter]?
    private struct QueryFilter: Codable {
      var field: String
      var `operator`: String
      var value: String
    private struct QueryResponse: Codable {
      var ids: [String]
    QueryRequest matches the structure of the input parameter the extension expects, according to the extension's documentation. It also contains a nested prefilter attribute that you will need later.QueryResponse matches the structure of the extension's response.
  6. Find the callable function specification and update the input and output types
    private lazy var vectorSearchQueryCallable: Callable<QueryRequest, QueryResponse> = functions.httpsCallable("ext-firestore-vector-search-queryCallable")
  7. Update the invocation of the callable function in performQuery
    private func performQuery(searchTerm: String) async -> [String] {
      do {
        let queryRequest = QueryRequest(query: searchTerm,
                                        limit: 2)
        let result = try await vectorSearchQueryCallable(queryRequest)
        return result.ids
      catch {
        return []

Run the app again

  1. Run the app again
  2. Type a search query that contains terms included in one of your notes
  3. You should now see a filtered list of notes

Screenshot of the app with the expected result

Pre-filter user data

Before you break out in dance to celebrate - there is a problem with the current version of the app: the result set contains data by all users.

You can verify this by running the app on a different simulator and adding more documents. The new documents will only show up in that simulator, if you run the app again on the other simulator, you will only see documents you created the first time around.

If you perform a search, you will notice that the call to vectorSearchQueryCallable returns document IDs that might belong to the other user. To prevent this, we need to use a prefilter.

In performQuery, update your code as follows:

  let prefilters: [QueryFilter] = if let uid = user?.uid {
    [QueryFilter(field: "userId", operator: "==", value: uid)]
  else {

  let queryRequest = QueryRequest(query: searchTerm,
                                  limit: 2,
                                  prefilters: prefilters)

This will pre-filter the data based on the logged-in user's ID As you might expect, this requires the Firestore index to be updated.

Run the following command from the command line to define a new Firestore index that includes both the userId and the vector embeddings in the embedding field.

gcloud alpha firestore indexes composite create --project=INSERT-YOUR-PROJECT-ID-HERE --collection-group=notes --query-scope=COLLECTION --field-config=order=ASCENDING,field-path=userId --field-config=vector-config='{"dimension":"768","flat": "{}"}',field-path=embedding

Once the index has finished building, run the app again to verify it works as expected

Prefiltered result set

8. Congratulations

Congratulations - on successfully completing this codelab!

In this codelab, you learned how to:

  • Set up a Cloud Firestore database with semantic search enabled.
  • Create a simple SwiftUI app to interact with the database.
  • Implement a search bar using SwiftUI's searchable view modifier and the task modifier.
  • Call a Cloud Function to perform a semantic search on the database, using the Firestore SDK's Callable interface.

With the knowledge you gained in this codelab, you can now build powerful applications that leverage the semantic search capabilities of Cloud Firestore to provide users with a more intuitive and efficient search experience.

To learn more about Firestore's new vector field and how to compute vector embeddings, check out the documentation.