K.8 Simple and Compound Queries

Perform Simple and Compound Queries in Cloud Firestore

Cloud Firestore provides powerful query functionality for specifying which documents you want to retrieve from a collection. These queries can also be used with either read() or addSnapshotListener(), as described in Get Data and Get Realtime Updates.

Example data

To get started, write some data about cities so we can look at different ways to read it back:

var cities:CollectionReference = Firestore.collection("cities");

var data1:Object = {};
data1.name = "San Francisco";
data1.state = "CA";
data1.country = "USA";
data1.capital = false;
data1.population = 860000;
cities.document("SF").write(data1);

var data2:Object = {};
data2.name = "Los Angeles";
data2.state = "CA";
data2.country = "USA";
data2.capital = false;
data2.population = 3900000;
cities.document("LA").write(data2);

var data3:Object = {};
data3.name = "Washington D.C.";
data3.state = null;
data3.country = "USA";
data3.capital = true;
data3.population = 680000;
cities.document("DC").write(data3);

var data4:Object = {};
data4.name = "Tokyo";
data4.state = null;
data4.country = "Japan";
data4.capital = true;
data4.population = 9000000;
cities.document("TOK").write(data4);

var data5:Object = {};
data5.name = "Beijing";
data5.state = null;
data5.country = "China";
data5.capital = true;
data5.population = 21500000;
cities.document("BJ").write(data5);

Simple queries

The following query returns all cities with state CA:

// Create a reference to the cities collection
var citiesRef:CollectionReference = Firestore.collection("cities");

// Create a query against the collection.
var query:Query = citiesRef.whereEqualTo("state", "CA");

The following query returns all the capital cities:

var capitalCities:Query = Firestore.collection("cities").whereEqualTo("capital", true);

Some example filters:

citiesRef.whereEqualTo("state", "CA");
citiesRef.whereLessThan("population", 100000);
citiesRef.whereGreaterThanOrEqualTo("name", "San Francisco");

Compound queries

You can also chain multiple where() methods to create more specific queries (logical AND).

citiesRef.whereEqualTo("state", "CO").whereEqualTo("name", "Denver");
citiesRef.whereEqualTo("state", "CA").whereLessThan("population", 1000000);

To learn more about valid and invalid queries, read here.