Batch DynamoDB Operations
Batch DynamoDB operations allow you to add multiple items in single mutation.
Step 1 - Define a custom mutation
import { type ClientSchema, a, defineData } from '@aws-amplify/backend';
const schema = a.schema({ // 1. Define your return type as a custom type or model Post: a.model({ id: a.id(), content: a.string(), likes: a.integer() }),
// 2. Define your mutation with the return type and, optionally, arguments BatchCreatePost: a .mutation() // arguments that this query accepts .arguments({ content: a.string().array() }) .returns(a.ref('Post').array()) // only allow signed-in users to call this API .authorization(allow => [allow.authenticated()])});
export type Schema = ClientSchema<typeof schema>;
export const data = defineData({ schema});Step 2 - Configure custom business logic handler code
After your query or mutation is defined, you need to author your custom business logic using a custom resolver powered by AppSync JavaScript resolver.
Custom resolvers work on a "request/response" basis. You choose a data source, map your request to the data source's input parameters, and then map the data source's response back to the query/mutation's return type. Custom resolvers provide the benefit of no cold starts, less infrastructure to manage, and no additional charge for Lambda function invocations. Review Choosing between custom resolver and function.
In your amplify/data/resource.ts file, define a custom handler using a.handler.custom.
import { type ClientSchema, a, defineData } from '@aws-amplify/backend';
const schema = a.schema({ Post: a.model({ id: a.id(), content: a.string(), likes: a.integer() }),
BatchCreatePost: a .mutation() .arguments({ contents: a.string().array() }) .returns(a.ref('Post').array()) .authorization(allow => [allow.authenticated()]) // 1. Add the custom handler .handler( a.handler.custom({ dataSource: a.ref('Post'), entry: './BatchCreatePostHandler.js', }) )});
export type Schema = ClientSchema<typeof schema>;
export const data = defineData({ schema});Amplify will store some values in the resolver context stash that can be accessed in the custom resolver.
| Name | Description |
|---|---|
| awsAppsyncApiId | The ID of the AppSync API. |
| amplifyApiEnvironmentName | The Amplify api environment name. (NONE in sandbox) |
The Amplify generated DynamoDB table names can be constructed from the variables in the context stash. The table name is in the format <model-name>-<aws-appsync-api-id>-<amplify-api-environment-name>. For example, the table name for the Post model would be Post-123456-dev where 123456 is the AppSync API ID and dev is the Amplify API environment name.
import { util } from '@aws-appsync/utils';
export function request(ctx) { var now = util.time.nowISO8601();
return { operation: 'BatchPutItem', tables: { [`Post-${ctx.stash.awsAppsyncApiId}-${ctx.stash.amplifyApiEnvironmentName}`]: ctx.args.contents.map((content) => util.dynamodb.toMapValues({ content, id: util.autoId(), createdAt: now, updatedAt: now, }) ), }, };}
export function response(ctx) { if (ctx.error) { util.error(ctx.error.message, ctx.error.type); } return ctx.result.data[`Post-${ctx.stash.awsAppsyncApiId}-${ctx.stash.amplifyApiEnvironmentName}`];}Step 3 - Invoke the custom query or mutation
From your generated Data client, you can find all your custom queries and mutations under the client.queries. and client.mutations. APIs respectively.
const { data, errors } = await client.mutations.BatchCreatePost({ contents: ['Post 1', 'Post 2', 'Post 3']});