Union (Transformation Stage)

Description

Merges the documents from another pipeline with those in the current pipeline.

Syntax

Node.js

  const 
  
 results 
  
 = 
  
 await 
  
 db 
 . 
 pipeline 
 () 
  
 . 
 collection 
 ( 
 "cities/SF/restaurants" 
 ) 
  
 . 
 union 
 ( 
 db 
 . 
 pipeline 
 (). 
 collection 
 ( 
 "cities/NYC/restaurants" 
 )) 
  
 . 
 execute 
 ();

Client examples

Node.js

  
 const 
  
 results 
  
 = 
  
 await 
  
 db 
 . 
 pipeline 
 () 
  
 . 
 collection 
 ( 
 "cities/SF/restaurants" 
 ) 
  
 . 
 where 
 ( 
 eq 
 ( 
 "type" 
 , 
  
 "chinese" 
 )) 
  
 . 
 union 
 ( 
 db 
 . 
 pipeline 
 () 
  
 . 
 collection 
 ( 
 "cities/NYC/restaurants" 
 ) 
  
 . 
 where 
 ( 
 eq 
 ( 
 "type" 
 , 
  
 "italian" 
 ))) 
  
 . 
 where 
 ( 
 gte 
 ( 
 "rating" 
 , 
  
 4.5 
 )) 
  
 . 
 execute 
 ();

Web

 const 
  
 results 
  
 = 
  
 await 
  
 execute 
 ( 
 db 
 . 
 pipeline 
 () 
  
 . 
 collection 
 ( 
 "cities/SF/restaurants" 
 ) 
  
 . 
 where 
 ( 
 field 
 ( 
 "type" 
 ). 
 equal 
 ( 
 "Chinese" 
 )) 
  
 . 
 union 
 ( 
 db 
 . 
 pipeline 
 () 
  
 . 
 collection 
 ( 
 "cities/NY/restaurants" 
 ) 
  
 . 
 where 
 ( 
 field 
 ( 
 "type" 
 ). 
 equal 
 ( 
 "Italian" 
 ))) 
  
 . 
 where 
 ( 
 field 
 ( 
 "rating" 
 ). 
 greaterThanOrEqual 
 ( 
 4.5 
 )) 
  
 . 
 sort 
 ( 
 field 
 ( 
 "__name__" 
 ). 
 descending 
 ()) 
 ); 
   test 
 . 
 firestore 
 . 
 js

Swift

 let 
  
 results 
  
 = 
  
 try 
  
 await 
  
 db 
 . 
 pipeline 
 () 
  
 . 
 collection 
 ( 
 "cities/SF/restaurants" 
 ) 
  
 . 
 where 
 ( 
 Field 
 ( 
 "type" 
 ). 
 equal 
 ( 
 "Chinese" 
 )) 
  
 . 
 union 
 ( 
 with 
 : 
  
 db 
 . 
 pipeline 
 () 
  
 . 
 collection 
 ( 
 "cities/NY/restaurants" 
 ) 
  
 . 
 where 
 ( 
 Field 
 ( 
 "type" 
 ). 
 equal 
 ( 
 "Italian" 
 ))) 
  
 . 
 where 
 ( 
 Field 
 ( 
 "rating" 
 ). 
 greaterThanOrEqual 
 ( 
 4.5 
 )) 
  
 . 
 sort 
 ([ 
 Field 
 ( 
 "__name__" 
 ). 
 descending 
 ()]) 
  
 . 
 execute 
 () 
   PipelineSnippets 
 . 
 swift

Kotlin
Android

 val 
  
 results 
  
 = 
  
 db 
 . 
 pipeline 
 () 
  
 . 
 collection 
 ( 
 "cities/SF/restaurants" 
 ) 
  
 . 
 where 
 ( 
 field 
 ( 
 "type" 
 ). 
 equal 
 ( 
 "Chinese" 
 )) 
  
 . 
 union 
 ( 
 db 
 . 
 pipeline 
 () 
  
 . 
 collection 
 ( 
 "cities/NY/restaurants" 
 ) 
  
 . 
 where 
 ( 
 field 
 ( 
 "type" 
 ). 
 equal 
 ( 
 "Italian" 
 ))) 
  
 . 
 where 
 ( 
 field 
 ( 
 "rating" 
 ). 
 greaterThanOrEqual 
 ( 
 4.5 
 )) 
  
 . 
 sort 
 ( 
 field 
 ( 
 "__name__" 
 ). 
 descending 
 ()) 
  
 . 
 execute 
 () 
   DocSnippets 
 . 
 kt

Java
Android

 Task<Pipeline 
 . 
 Snapshot 
>  
 results 
  
 = 
  
 db 
 . 
 pipeline 
 () 
  
 . 
 collection 
 ( 
 "cities/SF/restaurants" 
 ) 
  
 . 
 where 
 ( 
 field 
 ( 
 "type" 
 ). 
 equal 
 ( 
 "Chinese" 
 )) 
  
 . 
 union 
 ( 
 db 
 . 
 pipeline 
 () 
  
 . 
 collection 
 ( 
 "cities/NY/restaurants" 
 ) 
  
 . 
 where 
 ( 
 field 
 ( 
 "type" 
 ). 
 equal 
 ( 
 "Italian" 
 ))) 
  
 . 
 where 
 ( 
 field 
 ( 
 "rating" 
 ). 
 greaterThanOrEqual 
 ( 
 4.5 
 )) 
  
 . 
 sort 
 ( 
 field 
 ( 
 "__name__" 
 ). 
 descending 
 ()) 
  
 . 
 execute 
 (); 
   DocSnippets 
 . 
 java

Python

 from 
  
 google.cloud.firestore_v1.pipeline_expressions 
  
 import 
 Field 
 results 
 = 
 ( 
 client 
 . 
 pipeline 
 () 
 . 
 collection 
 ( 
 "cities/SF/restaurants" 
 ) 
 . 
 where 
 ( 
 Field 
 . 
 of 
 ( 
 "type" 
 ) 
 . 
 equal 
 ( 
 "Chinese" 
 )) 
 . 
 union 
 ( 
 client 
 . 
 pipeline 
 () 
 . 
 collection 
 ( 
 "cities/NY/restaurants" 
 ) 
 . 
 where 
 ( 
 Field 
 . 
 of 
 ( 
 "type" 
 ) 
 . 
 equal 
 ( 
 "Italian" 
 )) 
 ) 
 . 
 where 
 ( 
 Field 
 . 
 of 
 ( 
 "rating" 
 ) 
 . 
 greater_than_or_equal 
 ( 
 4.5 
 )) 
 . 
 sort 
 ( 
 Field 
 . 
 of 
 ( 
 "__name__" 
 ) 
 . 
 descending 
 ()) 
 . 
 execute 
 () 
 ) 
   firestore_pipelines 
 . 
 py

Java

 Pipeline 
 . 
 Snapshot 
  
 results 
  
 = 
  
 firestore 
  
 . 
 pipeline 
 () 
  
 . 
 collection 
 ( 
 "cities/SF/restaurants" 
 ) 
  
 . 
 where 
 ( 
 field 
 ( 
 "type" 
 ). 
 equal 
 ( 
 "Chinese" 
 )) 
  
 . 
 union 
 ( 
  
 firestore 
  
 . 
 pipeline 
 () 
  
 . 
 collection 
 ( 
 "cities/NY/restaurants" 
 ) 
  
 . 
 where 
 ( 
 field 
 ( 
 "type" 
 ). 
 equal 
 ( 
 "Italian" 
 ))) 
  
 . 
 where 
 ( 
 field 
 ( 
 "rating" 
 ). 
 greaterThanOrEqual 
 ( 
 4.5 
 )) 
  
 . 
 sort 
 ( 
 descending 
 ( 
 field 
 ( 
 "__name__" 
 ))) 
  
 . 
 execute 
 () 
  
 . 
 get 
 (); 
   PipelineSnippets 
 . 
 java

Behavior

This stage runs multiple pipelines in parallel and concatenates the results together.

Non-Deterministic Order of Results

The order in which results are combined between the two pipelines is non-deterministic. Any perceived order is unstable and shouldn't be relied upon. A following sort stage can be added if a stable order is required.

Node.js

  
 const 
  
 results 
  
 = 
  
 await 
  
 db 
 . 
 pipeline 
 () 
  
 . 
 collection 
 ( 
 "cities/SF/restaurants" 
 ) 
  
 . 
 where 
 ( 
 eq 
 ( 
 "type" 
 , 
  
 "chinese" 
 )) 
  
 . 
 union 
 ( 
 db 
 . 
 pipeline 
 () 
  
 . 
 collection 
 ( 
 "cities/NYC/restaurants" 
 ) 
  
 . 
 where 
 ( 
 eq 
 ( 
 "type" 
 , 
  
 "italian" 
 ))) 
  
 . 
 where 
 ( 
 gte 
 ( 
 "rating" 
 , 
  
 4.5 
 )) 
  
 . 
 sort 
 ( 
 Field 
 . 
 of 
 ( 
 "__name__" 
 )) 
  
 . 
 execute 
 ();

Kotlin
Android

 val 
  
 results 
  
 = 
  
 db 
 . 
 pipeline 
 () 
  
 . 
 collection 
 ( 
 "cities/SF/restaurants" 
 ) 
  
 . 
 where 
 ( 
 field 
 ( 
 "type" 
 ). 
 equal 
 ( 
 "Chinese" 
 )) 
  
 . 
 union 
 ( 
 db 
 . 
 pipeline 
 () 
  
 . 
 collection 
 ( 
 "cities/NY/restaurants" 
 ) 
  
 . 
 where 
 ( 
 field 
 ( 
 "type" 
 ). 
 equal 
 ( 
 "Italian" 
 ))) 
  
 . 
 where 
 ( 
 field 
 ( 
 "rating" 
 ). 
 greaterThanOrEqual 
 ( 
 4.5 
 )) 
  
 . 
 sort 
 ( 
 field 
 ( 
 "__name__" 
 ). 
 descending 
 ()) 
  
 . 
 execute 
 () 
   DocSnippets 
 . 
 kt

Java
Android

 Task<Pipeline 
 . 
 Snapshot 
>  
 results 
  
 = 
  
 db 
 . 
 pipeline 
 () 
  
 . 
 collection 
 ( 
 "cities/SF/restaurants" 
 ) 
  
 . 
 where 
 ( 
 field 
 ( 
 "type" 
 ). 
 equal 
 ( 
 "Chinese" 
 )) 
  
 . 
 union 
 ( 
 db 
 . 
 pipeline 
 () 
  
 . 
 collection 
 ( 
 "cities/NY/restaurants" 
 ) 
  
 . 
 where 
 ( 
 field 
 ( 
 "type" 
 ). 
 equal 
 ( 
 "Italian" 
 ))) 
  
 . 
 where 
 ( 
 field 
 ( 
 "rating" 
 ). 
 greaterThanOrEqual 
 ( 
 4.5 
 )) 
  
 . 
 sort 
 ( 
 field 
 ( 
 "__name__" 
 ). 
 descending 
 ()) 
  
 . 
 execute 
 (); 
   DocSnippets 
 . 
 java

Python

 from 
  
 google.cloud.firestore_v1.pipeline_expressions 
  
 import 
 Field 
 results 
 = 
 ( 
 client 
 . 
 pipeline 
 () 
 . 
 collection 
 ( 
 "cities/SF/restaurants" 
 ) 
 . 
 where 
 ( 
 Field 
 . 
 of 
 ( 
 "type" 
 ) 
 . 
 equal 
 ( 
 "Chinese" 
 )) 
 . 
 union 
 ( 
 client 
 . 
 pipeline 
 () 
 . 
 collection 
 ( 
 "cities/NY/restaurants" 
 ) 
 . 
 where 
 ( 
 Field 
 . 
 of 
 ( 
 "type" 
 ) 
 . 
 equal 
 ( 
 "Italian" 
 )) 
 ) 
 . 
 where 
 ( 
 Field 
 . 
 of 
 ( 
 "rating" 
 ) 
 . 
 greater_than_or_equal 
 ( 
 4.5 
 )) 
 . 
 sort 
 ( 
 Field 
 . 
 of 
 ( 
 "__name__" 
 ) 
 . 
 descending 
 ()) 
 . 
 execute 
 () 
 ) 
   firestore_pipelines 
 . 
 py

Java

 Pipeline 
 . 
 Snapshot 
  
 results 
  
 = 
  
 firestore 
  
 . 
 pipeline 
 () 
  
 . 
 collection 
 ( 
 "cities/SF/restaurants" 
 ) 
  
 . 
 where 
 ( 
 field 
 ( 
 "type" 
 ). 
 equal 
 ( 
 "Chinese" 
 )) 
  
 . 
 union 
 ( 
  
 firestore 
  
 . 
 pipeline 
 () 
  
 . 
 collection 
 ( 
 "cities/NY/restaurants" 
 ) 
  
 . 
 where 
 ( 
 field 
 ( 
 "type" 
 ). 
 equal 
 ( 
 "Italian" 
 ))) 
  
 . 
 where 
 ( 
 field 
 ( 
 "rating" 
 ). 
 greaterThanOrEqual 
 ( 
 4.5 
 )) 
  
 . 
 sort 
 ( 
 descending 
 ( 
 field 
 ( 
 "__name__" 
 ))) 
  
 . 
 execute 
 () 
  
 . 
 get 
 (); 
   PipelineSnippets 
 . 
 java

Duplicate Results

The union stage does not deduplicate results. A following distinct or aggregate stage can be added if duplicate results need to be removed.

Union (Transformation Stage)

Description

Syntax

Node.js

Client examples

Node.js

Web

Swift

Kotlin Android

Java Android

Python

Java

Behavior

Non-Deterministic Order of Results

Node.js

Kotlin Android

Java Android

Python

Java

Duplicate Results

Kotlin
Android

Java
Android

Kotlin
Android

Java
Android