Debugging Functions Reference

Debugging Functions

Name	Description
`EXISTS`	Returns `TRUE` if the value is not an absent value
`IS_ABSENT`	Returns `TRUE` if the value is an absent value
`IF_ABSENT`	Replaces the value with an expression if it is absent
`IS_ERROR`	Catches and checks if an error has been thrown by the underlying expression
`IF_ERROR`	Replaces the value with an expression if it has thrown an error

EXISTS

Syntax:

 exists(value: ANY) -> BOOLEAN

Description:

Returns TRUE if value is not the absent value.

Examples:

`value`	`exists(value)`
0L	`TRUE`
"foo"	`TRUE`
`NULL`	`TRUE`
`ABSENT`	`FALSE`

Node.js

 const 
  
 result 
  
 = 
  
 await 
  
 db 
 . 
 pipeline 
 () 
  
 . 
 collection 
 ( 
 "books" 
 ) 
  
 . 
 select 
 ( 
 field 
 ( 
 "rating" 
 ). 
 exists 
 (). 
 as 
 ( 
 "hasRating" 
 )) 
  
 . 
 execute 
 (); 
   test 
 . 
 firestore 
 . 
 js

Web

Example:

 const 
  
 result 
  
 = 
  
 await 
  
 execute 
 ( 
 db 
 . 
 pipeline 
 () 
  
 . 
 collection 
 ( 
 "books" 
 ) 
  
 . 
 select 
 ( 
 field 
 ( 
 "rating" 
 ). 
 exists 
 (). 
 as 
 ( 
 "hasRating" 
 )) 
 ); 
   test 
 . 
 firestore 
 . 
 js

Swift

 let 
  
 result 
  
 = 
  
 try 
  
 await 
  
 db 
 . 
 pipeline 
 () 
  
 . 
 collection 
 ( 
 "books" 
 ) 
  
 . 
 select 
 ([ 
 Field 
 ( 
 "rating" 
 ). 
 exists 
 (). 
 as 
 ( 
 "hasRating" 
 )]) 
  
 . 
 execute 
 () 
   PipelineSnippets 
 . 
 swift

Kotlin
Android

Example:

 val 
  
 result 
  
 = 
  
 db 
 . 
 pipeline 
 () 
  
 . 
 collection 
 ( 
 "books" 
 ) 
  
 . 
 select 
 ( 
 field 
 ( 
 "rating" 
 ). 
 exists 
 (). 
 alias 
 ( 
 "hasRating" 
 )) 
  
 . 
 execute 
 () 
   DocSnippets 
 . 
 kt

Java
Android

Example:

 Task<Pipeline 
 . 
 Snapshot 
>  
 result 
  
 = 
  
 db 
 . 
 pipeline 
 () 
  
 . 
 collection 
 ( 
 "books" 
 ) 
  
 . 
 select 
 ( 
 field 
 ( 
 "rating" 
 ). 
 exists 
 (). 
 alias 
 ( 
 "hasRating" 
 )) 
  
 . 
 execute 
 (); 
   DocSnippets 
 . 
 java

Python

 from 
  
 google.cloud.firestore_v1.pipeline_expressions 
  
 import 
 Field 
 result 
 = 
 ( 
 client 
 . 
 pipeline 
 () 
 . 
 collection 
 ( 
 "books" 
 ) 
 . 
 select 
 ( 
 Field 
 . 
 of 
 ( 
 "rating" 
 ) 
 . 
 exists 
 () 
 . 
 as_ 
 ( 
 "hasRating" 
 )) 
 . 
 execute 
 () 
 ) 
   firestore_pipelines 
 . 
 py

Java

 Pipeline 
 . 
 Snapshot 
  
 result 
  
 = 
  
 firestore 
  
 . 
 pipeline 
 () 
  
 . 
 collection 
 ( 
 "books" 
 ) 
  
 . 
 select 
 ( 
 exists 
 ( 
 field 
 ( 
 "rating" 
 )). 
 as 
 ( 
 "hasRating" 
 )) 
  
 . 
 execute 
 () 
  
 . 
 get 
 (); 
   PipelineSnippets 
 . 
 java

IS_ABSENT

Syntax:

 is_absent(value: ANY) -> BOOLEAN

Description:

Returns TRUE if value is the absent value, and FALSE otherwise. Absent values are values that are missing from the input, such as a missing document field.

Examples:

`value`	`is_absent(value)`
0L	`FALSE`
"foo"	`FALSE`
`NULL`	`FALSE`
`ABSENT`	`TRUE`

IF_ABSENT

Syntax:

 if_absent(value: ANY, replacement: ANY) -> ANY

Description:

If value is an absent value, evaluates and returns replacement . Otherwise returns value .

Examples:

`value`	`replacement`	`if_absent(value, replacement)`
5L	0L	5L
`NULL`	0L	`NULL`
`ABSENT`	0L	0L

IS_ERROR

Syntax:

 is_error(try: ANY) -> BOOLEAN

Description:

Returns TRUE if an error is thrown during the evaluation of try . Returns FALSE otherwise.

IF_ERROR

Syntax:

 if_error(try: ANY, catch: ANY) -> ANY

Description:

If an error is thrown during the evaluation of try , evaluates and returns replacement . Otherwise returns the resolved value of try .

What's next

See the Pipeline Queries overview

Debugging Functions Reference