I am new to AppSync and DynamoDB, sorry if this question is basic. I have an AppSync Resolver for this schema:

type Profile {
    name: String!
    location: String!
}

input ProfileInput {
    name: String!
    location: String!
}
type Mutation {
    createProfile(profileInput: ProfileInput!): Profile! @aws_cognito_user_pools @aws_api_key
    }

The resolvers are:

Request

{
    "version" : "2017-02-28",
    "operation" : "UpdateItem",
    "key" : {
        "name" : $util.dynamodb.toDynamoDBJson($ctx.identity.username),
        "attribute": $util.dynamodb.toDynamoDBJson("info")
    },
    "update" : {
        "expression" : "SET #p :da",
        "expressionNames" : {
            "#p" : "data"
        },
        "expressionValues" : {
            ":da" : $util.dynamodb.toDynamoDBJson($ctx.args.profileInput)
        }
    }
}

Response

$util.toJson($ctx.result)

The Request I am sending to Appsync :

mutation CreateProfileMutation {
  createProfile(profileInput: {location: "Updated Location", name: "Updated Username"}) {
    location
    name
  }
}

But Dynamodb is throwing this error:

{
  "data": null,
  "errors": [
    {
      "path": [
        "createProfile"
      ],
      "data": null,
      "errorType": "DynamoDB:DynamoDbException",
      "errorInfo": null,
      "locations": [
        {
          "line": 12,
          "column": 3,
          "sourceName": null
        }
      ],
      "message": "Invalid UpdateExpression: Syntax error; token: \":da\", near: \"#p :da\" (Service: DynamoDb, Status Code: 400, Request ID: some id, Extended Request ID: null)"
    }
  ]
}

The transformed template is:

{
"version" : "2017-02-28",
"operation" : "UpdateItem",
"key" : {
    "name" : {"S":"user#1"},
    "attribute": {"S":"info"}
},
"update" : {
    "expression" : "SET #p :da",
    "expressionNames" : {
        "#p" : "data"
    },
    "expressionValues" : {
        ":da" : {"M":{"name":{"S":"Updated Username"},"location":{"S":"Updated Location"}}}
    }
}

}

It looks like a syntax error, but I couldn't figure out what the error is. Any help is appreciated.

CodePudding user response：

The SET action in your update expression is missing the = operand.

It should be "expression" : "SET #p = :da" instead of "expression" : "SET #p :da".