Data model

Data model

Firestore is a NoSQL, document-oriented database. Unlike a SQL database, there are no tables or rows. Instead, you store data in documents, which are organized into collections.

Each document contains a set of key-value pairs. Firestore is optimized for storing large collections of small documents.

All documents must be stored in collections. Documents can contain subcollections and nested objects, both of which can include primitive fields like strings or complex objects like lists.

Collections and documents are created implicitly in Firestore. Simply assign data to a document within a collection. If either the collection or document does not exist, Firestore creates it.

Documents

In Firestore, the unit of storage is the document. A document is a lightweight record that contains fields, which map to values. Each document is identified by a name.

A document representing a user alovelace might look like this:

• alovelace

  first : "Ada"
last : "Lovelace"
born : 1815
  

Note: Firestore supports a variety of data types for values: boolean, number, string, geo point, binary blob, and timestamp. You can also use arrays or nested objects, called maps, to structure data within a document.

Complex, nested objects in a document are called maps. For example, you could structure the user's name from the example above with a map, like this:

• alovelace

  name :
    first : "Ada"
    last : "Lovelace"
born : 1815
  

You may notice that documents look a lot like JSON. In fact, they basically are. There are some differences (for example, documents support extra data types and are limited in size to 1 MB), but in general, you can treat documents as lightweight JSON records.

Collections

Documents live in collections, which are simply containers for documents. For example, you could have a users collection to contain your various users, each represented by a document:

• users

  • alovelace

    first : "Ada"
last : "Lovelace"
born : 1815
    

  • aturing

    first : "Alan"
last : "Turing"
born : 1912
    

Firestore is schemaless, so you have complete freedom over what fields you put in each document and what data types you store in those fields. Documents within the same collection can all contain different fields or store different types of data in those fields. However, it's a good idea to use the same fields and data types across multiple documents, so that you can query the documents more easily.

A collection contains documents and nothing else. It can't directly contain raw fields with values, and it can't contain other collections. (See Hierarchical Data for an explanation of how to structure more complex data in Firestore.)

The names of documents within a collection are unique. You can provide your own keys, such as user IDs, or you can let Firestore create random IDs for you automatically.

You do not need to "create" or "delete" collections. After you create the first document in a collection, the collection exists. If you delete all of the documents in a collection, it no longer exists.

References

Every document in Firestore is uniquely identified by its location within the database. The previous example showed a document alovelace within the collection users. To refer to this location in your code, you can create a reference to it.

Web version 9

Learn more about the tree-shakeable modular Web API and upgrade from the namespaced API.

import { doc } from "firebase/firestore";

const alovelaceDocumentRef = doc(db, 'users', 'alovelace');
doc_reference.js

Web version 8

Learn more about the tree-shakeable modular Web API and upgrade from the namespaced API.

var alovelaceDocumentRef = db.collection('users').doc('alovelace');
test.firestore.js

Swift

Note: This product is not available on watchOS and App Clip targets.

let alovelaceDocumentRef = db.collection("users").document("alovelace")
ViewController.swift

Objective-C

Note: This product is not available on watchOS and App Clip targets.

FIRDocumentReference *alovelaceDocumentRef =
    [[self.db collectionWithPath:@"users"] documentWithPath:@"alovelace"];
ViewController.m

Kotlin+KTX
Android

val alovelaceDocumentRef = db.collection("users").document("alovelace")
DocSnippets.kt

Java
Android

DocumentReference alovelaceDocumentRef = db.collection("users").document("alovelace");
DocSnippets.java

Dart

final alovelaceDocumentRef = db.collection("users").doc("alovelace");
firestore.dart

Java

// Reference to a document with id "alovelace" in the collection "users"
DocumentReference document = db.collection("users").document("alovelace");
References.java

Python

a_lovelace_ref = db.collection("users").document("alovelace")
snippets.py

Python
(Async)

a_lovelace_ref = db.collection("users").document("alovelace")
snippets.py

C++

DocumentReference alovelace_document_reference =
    db->Collection("users").Document("alovelace");
snippets.cpp

Node.js

const alovelaceDocumentRef = db.collection('users').doc('alovelace');
index.js

Go

import (
	"cloud.google.com/go/firestore"
)

func createDocReference(client *firestore.Client) {

	alovelaceRef := client.Collection("users").Doc("alovelace")

	_ = alovelaceRef
}
retrieve_data_reference_document.go

PHP

PHP

To authenticate to Firestore, set up Application Default Credentials. For more information, see Set up authentication for a local development environment.

$document = $db->collection('samples/php/users')->document('alovelace');

Unity

DocumentReference documentRef = db.Collection("users").Document("alovelace");

C#

C#

To authenticate to Firestore, set up Application Default Credentials. For more information, see Set up authentication for a local development environment.

DocumentReference documentRef = db.Collection("users").Document("alovelace");

Ruby

document_ref = firestore.col("users").doc("alovelace")
data_model.rb

A reference is a lightweight object that just points to a location in your database. You can create a reference whether or not data exists there, and creating a reference does not perform any network operations.

You can also create references to collections:

Web version 9

Learn more about the tree-shakeable modular Web API and upgrade from the namespaced API.

import { collection } from "firebase/firestore";

const usersCollectionRef = collection(db, 'users');
collection_reference.js

Web version 8

Learn more about the tree-shakeable modular Web API and upgrade from the namespaced API.

var usersCollectionRef = db.collection('users');
test.firestore.js

Swift

Note: This product is not available on watchOS and App Clip targets.

let usersCollectionRef = db.collection("users")
ViewController.swift

Objective-C

Note: This product is not available on watchOS and App Clip targets.

FIRCollectionReference *usersCollectionRef = [self.db collectionWithPath:@"users"];
ViewController.m

Kotlin+KTX
Android

val usersCollectionRef = db.collection("users")
DocSnippets.kt

Java
Android

CollectionReference usersCollectionRef = db.collection("users");
DocSnippets.java

Dart

final usersCollectionRef = db.collection("users");
firestore.dart

Java

// Reference to the collection "users"
CollectionReference collection = db.collection("users");
References.java

Python

users_ref = db.collection("users")
snippets.py

Python
(Async)

users_ref = db.collection("users")
snippets.py

C++

CollectionReference users_collection_reference = db->Collection("users");
snippets.cpp

Node.js

const usersCollectionRef = db.collection('users');
index.js

Go

import (
	"cloud.google.com/go/firestore"
)

func createCollectionReference(client *firestore.Client) {
	usersRef := client.Collection("users")

	_ = usersRef
}
retrieve_data_reference_collection.go

PHP

PHP

To authenticate to Firestore, set up Application Default Credentials. For more information, see Set up authentication for a local development environment.

$collection = $db->collection('samples/php/users');

Unity

CollectionReference collectionRef = db.Collection("users");

C#

C#

To authenticate to Firestore, set up Application Default Credentials. For more information, see Set up authentication for a local development environment.

CollectionReference collectionRef = db.Collection("users");

Ruby

collection_ref = firestore.col "users"
data_model.rb

Note: Collection references and document references are two distinct types of references and let you perform different operations. For example, you could use a collection reference for querying the documents in the collection, and you could use a document reference to read or write an individual document.

For convenience, you can also create references by specifying the path to a document or collection as a string, with path components separated by a forward slash (/). For example, to create a reference to the alovelace document:

Web version 9

Learn more about the tree-shakeable modular Web API and upgrade from the namespaced API.

import { doc } from "firebase/firestore"; 

const alovelaceDocumentRef = doc(db, 'users/alovelace');
doc_reference_alternative.js

Web version 8

Learn more about the tree-shakeable modular Web API and upgrade from the namespaced API.

var alovelaceDocumentRef = db.doc('users/alovelace');
test.firestore.js

Swift

Note: This product is not available on watchOS and App Clip targets.

let aLovelaceDocumentReference = db.document("users/alovelace")
ViewController.swift

Objective-C

Note: This product is not available on watchOS and App Clip targets.

FIRDocumentReference *aLovelaceDocumentReference =
    [self.db documentWithPath:@"users/alovelace"];
ViewController.m

Kotlin+KTX
Android

val alovelaceDocumentRef = db.document("users/alovelace")
DocSnippets.kt

Java
Android

DocumentReference alovelaceDocumentRef = db.document("users/alovelace");
DocSnippets.java

Dart

final aLovelaceDocRef = db.doc("users/alovelace");
firestore.dart

Java

// Reference to a document with id "alovelace" in the collection "users"
DocumentReference document = db.document("users/alovelace");
References.java

Python

a_lovelace_ref = db.document("users/alovelace")
snippets.py

Python
(Async)

a_lovelace_ref = db.document("users/alovelace")
snippets.py

C++

DocumentReference alovelace_document = db->Document("users/alovelace");
snippets.cpp

Node.js

const alovelaceDocumentRef = db.doc('users/alovelace');
index.js

Go

import (
	"cloud.google.com/go/firestore"
)

func createDocReferenceFromString(client *firestore.Client) {
	// Reference to a document with id "alovelace" in the collection "users"
	alovelaceRef := client.Doc("users/alovelace")

	_ = alovelaceRef
}
retrieve_data_reference_document_path.go

PHP

PHP

To authenticate to Firestore, set up Application Default Credentials. For more information, see Set up authentication for a local development environment.

$document = $db->document('users/alovelace');

Unity

DocumentReference documentRef = db.Document("users/alovelace");

C#

C#

To authenticate to Firestore, set up Application Default Credentials. For more information, see Set up authentication for a local development environment.

DocumentReference documentRef = db.Document("users/alovelace");

Ruby

document_path_ref = firestore.doc "users/alovelace"
data_model.rb

Hierarchical Data

To understand how hierarchical data structures work in Firestore, consider an example chat app with messages and chat rooms.

You can create a collection called rooms to store different chat rooms:

• rooms

  • roomA

    name : "my chat room"
    

  • roomB

    ...
    

Now that you have chat rooms, decide how to store your messages. You might not want to store them in the chat room's document. Documents in Firestore should be lightweight, and a chat room could contain a large number of messages. However, you can create additional collections within your chat room's document, as subcollections.

Subcollections

The best way to store messages in this scenario is by using subcollections. A subcollection is a collection associated with a specific document.

Note: You can query across subcollections with the same collection ID by using Collection Group Queries.

You can create a subcollection called messages for every room document in your rooms collection:

• rooms

  • roomA

    name : "my chat room"
    

    • messages

      • message1

        from : "alex"
msg : "Hello World!"
        

      • message2

        ...
        

  • roomB

    ...
    

In this example, you would create a reference to a message in the subcollection with the following code:

Web version 9

Learn more about the tree-shakeable modular Web API and upgrade from the namespaced API.

import { doc } from "firebase/firestore"; 

const messageRef = doc(db, "rooms", "roomA", "messages", "message1");
subcollection_reference.js

Web version 8

Learn more about the tree-shakeable modular Web API and upgrade from the namespaced API.

var messageRef = db.collection('rooms').doc('roomA')
                .collection('messages').doc('message1');
test.firestore.js

Swift

Note: This product is not available on watchOS and App Clip targets.

let messageRef = db
  .collection("rooms").document("roomA")
  .collection("messages").document("message1")
ViewController.swift

Objective-C

Note: This product is not available on watchOS and App Clip targets.

FIRDocumentReference *messageRef =
    [[[[self.db collectionWithPath:@"rooms"] documentWithPath:@"roomA"]
    collectionWithPath:@"messages"] documentWithPath:@"message1"];
ViewController.m

Kotlin+KTX
Android

val messageRef = db
    .collection("rooms").document("roomA")
    .collection("messages").document("message1")
DocSnippets.kt

Java
Android

DocumentReference messageRef = db
        .collection("rooms").document("roomA")
        .collection("messages").document("message1");
DocSnippets.java

Dart

final messageRef = db
    .collection("rooms")
    .doc("roomA")
    .collection("messages")
    .doc("message1");
firestore.dart

Java

// Reference to a document in subcollection "messages"
DocumentReference document =
    db.collection("rooms").document("roomA").collection("messages").document("message1");
References.java

Python

room_a_ref = db.collection("rooms").document("roomA")
message_ref = room_a_ref.collection("messages").document("message1")
snippets.py

Python
(Async)

room_a_ref = db.collection("rooms").document("roomA")
message_ref = room_a_ref.collection("messages").document("message1")
snippets.py

C++

DocumentReference message_reference = db->Collection("rooms")
    .Document("roomA")
    .Collection("messages")
    .Document("message1");
snippets.cpp

Node.js

const messageRef = db.collection('rooms').doc('roomA')
  .collection('messages').doc('message1');
index.js

Go

import (
	"cloud.google.com/go/firestore"
)

func createSubcollectionReference(client *firestore.Client) {
	messageRef := client.Collection("rooms").Doc("roomA").
		Collection("messages").Doc("message1")

	_ = messageRef
}
retrieve_data_reference_subcollection.go

PHP

PHP

To authenticate to Firestore, set up Application Default Credentials. For more information, see Set up authentication for a local development environment.

$document = $db
    ->collection('rooms')
    ->document('roomA')
    ->collection('messages')
    ->document('message1');

Unity

DocumentReference documentRef = db
	.Collection("Rooms").Document("RoomA")
	.Collection("Messages").Document("Message1");

C#

C#

To authenticate to Firestore, set up Application Default Credentials. For more information, see Set up authentication for a local development environment.

DocumentReference documentRef = db
    .Collection("Rooms").Document("RoomA")
    .Collection("Messages").Document("Message1");

Ruby

message_ref = firestore.col("rooms").doc("roomA").col("messages").doc("message1")
data_model.rb

Notice the alternating pattern of collections and documents. Your collections and documents must always follow this pattern. You cannot reference a collection in a collection or a document in a document.

Subcollections allow you to structure data hierarchically, making data easier to access. To get all messages in roomA, you can create a collection reference to the subcollection messages and interact with it like you would any other collection reference.

Documents in subcollections can contain subcollections as well, allowing you to further nest data. You can nest data up to 100 levels deep.

Warning: Deleting a document does not delete its subcollections!

When you delete a document that has subcollections, those subcollections are not deleted. For example, there may be a document located at coll/doc/subcoll/subdoc even though the document coll/doc no longer exists. If you want to delete documents in subcollections when deleting a parent document, you must do so manually, as shown in Delete Collections.