appwrite/docs/examples/1.8.x/server-dart/examples/databases/upsert-documents.md

import 'package:dart_appwrite/dart_appwrite.dart';

Client client = Client()
    .setEndpoint('https://<REGION>.cloud.appwrite.io/v1') // Your API Endpoint
    .setProject('<YOUR_PROJECT_ID>') // Your project ID
    .setKey('<YOUR_API_KEY>'); // Your secret API key

Databases databases = Databases(client);

DocumentList result = await databases.upsertDocuments(
    databaseId: '<DATABASE_ID>',
    collectionId: '<COLLECTION_ID>',
    documents: [],
    transactionId: '<TRANSACTION_ID>', // (optional)
);