How To Use The Same GraphQL Query Multiple Times In A Single API Call. Amplify, DynamoDB

Question

The user will input multiple usernames and I would like to search my DynamoDB table for all each user's id in a single API call. The following is the important portion of the graphql user schema:

type User
  @model
  @key(name: "byName", fields: ["username"], queryField: "findUsername")
   {
  id: ID!
  email: AWSEmail!
  username: String!
  firstName: String
  lastName: String
  createdAt: AWSDateTime
  updatedAt: AWSDateTime
} 

I would like to create a query which takes the list of usernames and returns each user's user id in a single api call. I am not sure how to dynamically and separately add the usernames to a query. Btw, I am using aws-amplify to help with dynamodb and graphql. This is also a React Native project.

Answer 1

You can run multiple queries and mutations using batch operations in AWS AppSync. Eg: BatchGetItem

type Post {
    id: ID!
    title: String
}

type Query {
    batchGet(ids: [ID]): [Post]
}

Sample query

query get {
    batchGet(ids:[1,2,3]){
        id
        title
    }
}

batchGet.request.vtl

#set($ids = [])
#foreach($id in ${ctx.args.ids})
    #set($map = {})
    $util.qr($map.put("id", $util.dynamodb.toString($id)))
    $util.qr($ids.add($map))
#end

{
    "version" : "2018-05-29",
    "operation" : "BatchGetItem",
    "tables" : {
        "Posts": {
            "keys": $util.toJson($ids),
            "consistentRead": true
        }
    }
}

batchGet.response.vtl

$util.toJson($ctx.result.data.Posts)

For more details check out this tutorial. https://docs.aws.amazon.com/appsync/latest/devguide/tutorial-dynamodb-batch.html