Add fields

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"))
);
test.firestore.js
Swift
let result = try await db.pipeline()
  .collection("books")
  .select([Field("soldBooks").add(Field("unsoldBooks")).as("totalBooks")])
  .execute()
PipelineSnippets.swift

Kotlin

val result = db.pipeline()
    .collection("books")
    .select(Expression.add(field("soldBooks"), field("unsoldBooks")).alias("totalBooks"))
    .execute()
DocSnippets.kt

Java

Task<Pipeline.Snapshot> result = db.pipeline()
    .collection("books")
    .select(Expression.add(field("soldBooks"), field("unsoldBooks")).alias("totalBooks"))
    .execute();
DocSnippets.java
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()
)
firestore_pipelines.py
Java
Pipeline.Snapshot result =
    firestore
        .pipeline()
        .collection("books")
        .select(add(field("soldBooks"), field("unsoldBooks")).as("totalBooks"))
        .execute()
        .get();
PipelineSnippets.java

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.