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.
Syntax
Node.js
const
results
=
await
db
.
pipeline
()
.
collection
(
"/users"
)
.
addFields
(
field
(
'first_name'
).
concat
(
' '
,
field
(
'last_name'
)).
as
(
'full_name'
))
.
execute
();
Client 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
();
Nesting Fields
While the alias assigned to the newly added fields can contain special
characters like .
, these are treated as top-level fields. For example:
Node.js
const
results
=
await
db
.
pipeline
()
.
collection
(
"/users"
)
.
addFields
(
field
(
'address.city'
).
toLower
().
as
(
'address.city'
))
.
execute
();
adds a new top-level field address.city
rather than merging the result of
the expression back into the nested map under address
.
