Add Fields (Transformation Stage)
Description
Add new fields to the documents produced by the previous stage.
The generated documents will contain all the fields from the previous stage
along with all newly added fields, overwriting any field that shares the same
name from the previous document. The add_fields(...)
stage allows updating
nested fields by specifying a nested field name as the alias.
Examples
Web
const result = await execute ( db . pipeline () . collection ( "books" ) . select ( field ( "soldBooks" ). add ( field ( "unsoldBooks" )). as ( "totalBooks" )) );
Swift
let result = try await db . pipeline () . collection ( "books" ) . select ([ Field ( "soldBooks" ). add ( Field ( "unsoldBooks" )). as ( "totalBooks" )]) . execute ()
Kotlin
Android
val result = db . pipeline () . collection ( "books" ) . select ( Expression . add ( field ( "soldBooks" ), field ( "unsoldBooks" )). alias ( "totalBooks" )) . execute ()
Java
Android
Task<Pipeline . Snapshot > result = db . pipeline () . collection ( "books" ) . select ( Expression . add ( field ( "soldBooks" ), field ( "unsoldBooks" )). alias ( "totalBooks" )) . execute ();
Python
from google.cloud.firestore_v1.pipeline_expressions import Field result = ( client . pipeline () . collection ( "books" ) . select ( Field . of ( "soldBooks" ) . add ( Field . of ( "unsoldBooks" )) . as_ ( "totalBooks" )) . execute () )
Java
Pipeline . Snapshot result = firestore . pipeline () . collection ( "books" ) . select ( add ( field ( "soldBooks" ), field ( "unsoldBooks" )). as ( "totalBooks" )) . execute () . get ();
Behavior
Overlapping Fields
Assigning an expression an alias that is already in the documents from the
previous stage will cause the add_fields(...)
stage to overwrite the previous
field. This can be used to chain up multiple expressions over the same field
name, like:
Node.js
const
results
=
await
db
.
pipeline
()
.
collection
(
"/users"
)
.
addFields
(
field
(
'age'
).
abs
().
as
(
'age'
))
.
addFields
(
field
(
'age'
).
add
(
10
).
as
(
'age'
))
.
execute
();
Nested Fields
Nested fields (e.g. those with .
syntax) can be updated as part of this
stage. This makes it possible to update a field "in-place" such as in:
Node.js
const
results
=
await
db
.
pipeline
()
.
collection
(
"/users"
)
.
addFields
(
field
(
'address.city'
).
toLower
().
as
(
'address.city'
))
.
execute
();
Assigning an expression to a nested field will implicitly create any missing parent fields as well.
