How to update row using increment either way set or add in amplify gen2? data client

[jaimeardp]

Amplify CLI Version

10.8.1

Question

Environment information

System:
  OS: Windows 11 10.0.22631
  CPU: (12) x64 12th Gen Intel(R) Core(TM) i7-1255U
  Memory: 1.11 GB / 15.73 GB
Binaries:
  Node: 20.16.0 - C:\Program Files\nodejs\node.EXE
  Yarn: undefined - undefined
  npm: 10.8.1 - C:\Program Files\nodejs\npm.CMD
  pnpm: undefined - undefined
NPM Packages:
  @aws-amplify/backend: 1.0.4
  @aws-amplify/backend-cli: 1.1.1
  aws-amplify: 6.4.0
  aws-cdk: 2.149.0
  aws-cdk-lib: 2.149.0
  typescript: 5.5.3
AWS environment variables:
  AWS_NODEJS_CONNECTION_REUSE_ENABLED = 1
  AWS_SDK_LOAD_CONFIG = 1
  AWS_STS_REGIONAL_ENDPOINTS = regional

Actually, searching in documentation, I found a simple example of update, just only "replace" old value by new value.

import { generateClient } from 'aws-amplify/data';
import { type Schema } from '../amplify/data/resource';

const client = generateClient<Schema>();

const todo = {
  id: 'some_id',
  content: 'Updated content',
};

const { data: updatedTodo, errors } = await client.models.Todo.update(todo);

But my use case is a increment, because i need to update column like views or counter in post. I understand that i can first to use "client.models.Blog.get" and after to use "client.models.Blog.update". But then is needed to perfom both requests for to update one simple "Atomic counters" in DynamoDB ?

Please if you face use case, recommend me, thanks.

I hope this in amplify gen2 data client.

aws dynamodb update-item \
--table-name counter \
--key '{"pk":{"S":"abc123"}}' \
--update-expression "ADD quantity :change" \
--expression-attribute-values file://values.json

json file

{
    ":change" : { "N" : "-5" }
}

[chrisbonifacio]

Hi @jaimeardp in order to implement an atomic counter with Amplify Gen 2, I would recommend adding a custom mutation to your schema and execute the DynamoDB operation in an AppSync JS resolver.

Please refer to our docs on custom operations and let us know if you run into any issues along the way:
https://docs.amplify.aws/react/build-a-backend/data/custom-business-logic/