firestore: query data

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 get() or addSnapshotListener(), as described in Get Data and Get Realtime Updates.

Note:  While the code samples cover multiple languages, the text explaining the samples refers to the Web method names.

Example data

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

WEB

SWIFT

OBJECTIVE-C

ANDROID

JAVA

PYTHON

MORE

FIRCollectionReference * citiesRef = [ self . db collectionWithPath :@ "cities" ];
[[ citiesRef documentWithPath :@ "SF" ] setData :@{
  @ "name" : @ "San Francisco" ,
  @ "state" : @ "CA" ,
  @ "country" : @ "USA" ,
  @ "capital" : @( NO ),
  @ "population" : @ 860000
}];
[[ citiesRef documentWithPath :@ "LA" ] setData :@{
  @ "name" : @ "Los Angeles" ,
  @ "state" : @ "CA" ,
  @ "country" : @ "USA" ,
  @ "capital" : @( NO ),
  @ "population" : @ 3900000
}];
[[ citiesRef documentWithPath :@ "DC" ] setData :@{
  @ "name" : @ "Washington D.C." ,
  @ "country" : @ "USA" ,
  @ "capital" : @( YES ),
  @ "population" : @ 680000
}];
[[ citiesRef documentWithPath :@ "TOK" ] setData :@{
  @ "name" : @ "Tokyo" ,
  @ "country" : @ "Japan" ,
  @ "capital" : @( YES ),
  @ "population" : @ 9000000
}];
[[ citiesRef documentWithPath :@ "BJ" ] setData :@{
  @ "name" : @ "Beijing" ,
  @ "country" : @ "China" ,
  @ "capital" : @( YES ),
  @ "population" : @ 21500000
}];

ViewController.m

 

Simple queries

The following query returns all cities with state CA:

WEB

SWIFT

OBJECTIVE-C

ANDROID

JAVA

PYTHON

MORE

// Create a reference to the cities collection
FIRCollectionReference * citiesRef = [ self . db collectionWithPath :@ "cities" ];
// Create a query against the collection.
FIRQuery * query = [ citiesRef queryWhereField :@ "state" isEqualTo :@ "CA" ];

ViewController.m

 

The following query returns all the capital cities:

WEB

SWIFT

OBJECTIVE-C

ANDROID

JAVA

PYTHON

MORE

FIRQuery * capitalCities =
    [[ self . db collectionWithPath :@ "cities" ] queryWhereField :@ "capital" isEqualTo : @YES ];

ViewController.m

 

The where() method takes three parameters: a field to filter on, a comparison operation, and a value. The comparison can be <, <=, ==, >, or >=. For iOS, Android, and Java, the comparison operator is explicitly named in the method.

Some example filters:

WEB

SWIFT

OBJECTIVE-C

ANDROID

JAVA

PYTHON

MORE

[ citiesRef queryWhereField :@ "state" isEqualTo :@ "CA" ];
[ citiesRef queryWhereField :@ "population" isLessThan :@ 100000 ];
[ citiesRef queryWhereField :@ "name" isGreaterThanOrEqualTo :@ "San Francisco" ];

ViewController.m

 

Compound queries

You can also chain multiple where() methods to create more specific queries (logical AND). However, to combine the equality operator (==) with a range comparison (<, <=, >, or >=), make sure to create a custom index.

WEB

SWIFT

OBJECTIVE-C

ANDROID

JAVA

PYTHON

MORE

[[ citiesRef queryWhereField :@ "state" isEqualTo :@ "CO" ]
    queryWhereField :@ "name" isGreaterThanOrEqualTo :@ "Denver" ];
[[ citiesRef queryWhereField :@ "state" isEqualTo :@ "CA" ]
    queryWhereField :@ "population" isLessThan :@ 1000000 ];

ViewController.m

 

Additionally, you can only perform range comparisons (<, <=, >, >=) on a single field:

Valid: Range filters on only one field

WEB

SWIFT

OBJECTIVE-C

ANDROID

JAVA

PYTHON

MORE

[[ citiesRef queryWhereField :@ "state" isGreaterThanOrEqualTo :@ "CA" ]
    queryWhereField :@ "state" isLessThanOrEqualTo :@ "IN" ];
[[ citiesRef queryWhereField :@ "state" isEqualTo :@ "CA" ]
    queryWhereField :@ "population" isGreaterThan :@ 1000000 ];

ViewController.m

 

Invalid: Range filters on different fields

WEB

SWIFT

OBJECTIVE-C

ANDROID

JAVA

PYTHON

MORE

[[ citiesRef queryWhereField :@ "state" isGreaterThanOrEqualTo :@ "CA" ]
    queryWhereField :@ "population" isGreaterThan :@ 1000000 ];

ViewController.m