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// Copyright 2017 Google Inc. All Rights Reserved.
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// See the License for the specific language governing permissions and
// limitations under the License.
// DO NOT EDIT doc.go. Modify internal/doc.template, then run make -C internal.
Package firestore provides a client for reading and writing to a Cloud Firestore
See for an introduction
to Cloud Firestore and additional help on using the Firestore API.
Note: you can't use both Cloud Firestore and Cloud Datastore in the same
Creating a Client
To start working with this package, create a client with a project ID:
ctx := context.Background()
client, err := firestore.NewClient(ctx, "projectID")
if err != nil {
// TODO: Handle error.
CollectionRefs and DocumentRefs
In Firestore, documents are sets of key-value pairs, and collections are groups of
documents. A Firestore database consists of a hierarchy of alternating collections
and documents, referred to by slash-separated paths like
This client is built around references to collections and documents. CollectionRefs
and DocumentRefs are lightweight values that refer to the corresponding database
entities. Creating a ref does not involve any network traffic.
states := client.Collection("States")
ny := states.Doc("NewYork")
// Or, in a single call:
ny = client.Doc("States/NewYork")
Use DocumentRef.Get to read a document. The result is a DocumentSnapshot.
Call its Data method to obtain the entire document contents as a map.
docsnap, err := ny.Get(ctx)
if err != nil {
// TODO: Handle error.
dataMap := docsnap.Data()
You can also obtain a single field with DataAt, or extract the data into a struct
with DataTo. With the type definition
type State struct {
Capital string `firestore:"capital"`
Population float64 `firestore:"pop"` // in millions
we can extract the document's data into a value of type State:
var nyData State
if err := docsnap.DataTo(&nyData); err != nil {
// TODO: Handle error.
Note that this client supports struct tags beginning with "firestore:" that work like
the tags of the encoding/json package, letting you rename fields, ignore them, or
omit their values when empty.
To retrieve multiple documents from their references in a single call, use
docsnaps, err := client.GetAll(ctx, []*firestore.DocumentRef{
states.Doc("Wisconsin"), states.Doc("Ohio"),
if err != nil {
// TODO: Handle error.
for _, ds := range docsnaps {
_ = ds // TODO: Use ds.
For writing individual documents, use the methods on DocumentReference.
Create creates a new document.
wr, err := ny.Create(ctx, State{
Capital: "Albany",
Population: 19.8,
if err != nil {
// TODO: Handle error.
The first return value is a WriteResult, which contains the time
at which the document was updated.
Create fails if the document exists. Another method, Set, either replaces an existing
document or creates a new one.
ca := states.Doc("California")
_, err = ca.Set(ctx, State{
Capital: "Sacramento",
Population: 39.14,
To update some fields of an existing document, use Update. It takes a list of
paths to update and their corresponding values.
_, err = ca.Update(ctx, []firestore.Update{{Path: "capital", Value: "Sacramento"}})
Use DocumentRef.Delete to delete a document.
_, err = ny.Delete(ctx)
You can condition Deletes or Updates on when a document was last changed. Specify
these preconditions as an option to a Delete or Update method. The check and the
write happen atomically with a single RPC.
docsnap, err = ca.Get(ctx)
if err != nil {
// TODO: Handle error.
_, err = ca.Update(ctx,
[]firestore.Update{{Path: "capital", Value: "Sacramento"}},
Here we update a doc only if it hasn't changed since we read it.
You could also do this with a transaction.
To perform multiple writes at once, use a WriteBatch. Its methods chain
for convenience.
WriteBatch.Commit sends the collected writes to the server, where they happen
writeResults, err := client.Batch().
Create(ny, State{Capital: "Albany"}).
Update(ca, []firestore.Update{{Path: "capital", Value: "Sacramento"}}).
You can use SQL to select documents from a collection. Begin with the collection, and
build up a query using Select, Where and other methods of Query.
q := states.Where("pop", ">", 10).OrderBy("pop", firestore.Desc)
Call the Query's Documents method to get an iterator, and use it like
the other Google Cloud Client iterators.
iter := q.Documents(ctx)
for {
doc, err := iter.Next()
if err == iterator.Done {
if err != nil {
// TODO: Handle error.
To get all the documents in a collection, you can use the collection itself
as a query.
iter = client.Collection("States").Documents(ctx)
Use a transaction to execute reads and writes atomically. All reads must happen
before any writes. Transaction creation, commit, rollback and retry are handled for
you by the Client.RunTransaction method; just provide a function and use the
read and write methods of the Transaction passed to it.
ny := client.Doc("States/NewYork")
err := client.RunTransaction(ctx, func(ctx context.Context, tx *firestore.Transaction) error {
doc, err := tx.Get(ny) // tx.Get, NOT ny.Get!
if err != nil {
return err
pop, err := doc.DataAt("pop")
if err != nil {
return err
return tx.Update(ny, []firestore.Update{{Path: "pop", Value: pop.(float64) + 0.2}})
if err != nil {
// TODO: Handle error.
See examples of authorization and authentication at
package firestore