Optional Query.getDestinationsByState

[idkjs]

Hey folks. Thanks for sharing this. So many good bits, especially on resolver mapping.

I can't get the optional resolver to resolve.

Using the suggested mapping:

{
    "version": "2017-02-28",
    "operation": "Query",
    "index":"state-index",
    "query":{
    	"expression":"#state = :state",
        "expressionNames":{
        	"#state":"state"
        },
        "expressionValues":{
        	":state" :{
            	"S": $util.dynamodb.toDynamoDBJson($ctx.args.state),
            }
        }
    }
}

with this default request mapping template:

## Pass back the result from DynamoDB. **
$util.toJson($ctx.result.items)

• called with this query:

query GetByState {
  getDestinationsByState(state:"Florida"){
    id
    description
  }
}

• returns this error:

{
  "data": {
    "getDestinationsByState": null
  },
  "errors": [
    {
      "path": [
        "getDestinationsByState"
      ],
      "data": null,
      "errorType": "MappingTemplate",
      "errorInfo": null,
      "locations": [
        {
          "line": 14,
          "column": 3,
          "sourceName": null
        }
      ],
      "message": "Value for field '$[query][expressionValues][:state][S]' must be text."
    }
  ]
}

• example from aws docs

{
    "version": "2017-02-28",
    "operation": "Query",
    "index": "todoid-index",
    "query": {
        "expression": "todoid = :todoid",
        "expressionValues": {
            ":todoid": {
                "S": "$context.source.id"
            }
        }
    }
}

I'm thinking the solution is to create an index called state-index. We can only create a secondary index when we create the dynamodb table. What would you suggest is the best way to go about setting up the optional query?

Thanks.

[idkjs]

Solution

1. Change the suggested mapping expressionValues key to the following to deal with

 "message": "Value for field '$[query][expressionValues][:state][S]' must be text."

error:

{
    "version": "2017-02-28",
    "operation": "Query",
    "index":"state-index",
    "query":{
    	"expression":"#state = :state",
        "expressionNames":{
        	"#state":"state"
        },
        "expressionValues":{
        	":state" : $util.dynamodb.toDynamoDBJson($ctx.args.state),
            
        }
    }
}

2. Create state-index index with partition key state.

3. Running query from above returns:

{
  "data": {
    "getDestinationsByState": [
      {
        "id": "b7214nf8-4242-40nc-b68a-15f212xxxxx",
        "description": "Disney World"
      }
    ]
  }
}

This works but is it the best way?

Thanks.