Auto-generated list resolver templates limits before filtering

It was kinda weird discovering that auto-generated appsync list query resolvers limit the scanned result before it filters. Part of this weirdness could be attributed to ignorance on dynamo usage on my part but part of this is also due to un-intuitive behavior which was not expected.

I ran this particular query :-

query ListRounds{
  listRounds(
    limit:10,
    filter:{
    	jobOpeningId:{
    		eq:"jobOpening-Company1College1drive1"
      }
  	})
  {
    items{
      id
    }
    nextToken
  }
}

It did not return rounds, even though they exist as the filter was applied on the limited result.

The default request resolver is:-

#set( $limit = $util.defaultIfNull($context.args.limit, 10) )
#set( $ListRequest = {
  "version": "2017-02-28",
  "limit": $limit
} )
#if( $context.args.nextToken )
  #set( $ListRequest.nextToken = "$context.args.nextToken" )
#end
#if( $context.args.filter )
  #set( $ListRequest.filter = $util.parseJson("$util.transform.toDynamoDBFilterExpression($ctx.args.filter)") )
#end
#if( !$util.isNull($modelQueryExpression) && !$util.isNullOrEmpty($modelQueryExpression.expression) )
  $util.qr($ListRequest.put("operation", "Query"))
  $util.qr($ListRequest.put("query", $modelQueryExpression))
#else
  $util.qr($ListRequest.put("operation", "Scan"))
#end
$util.toJson($ListRequest)

Q1 - What is $modelQueryExpression in this template?

Q2 - How can this template be modified to use query expression with indexName i.e query instead of scan?

What AWS Services are you utilizing? aws-amplify version 1.7.8

[RossWilliams]

Regarding Q1, that is an object that holds data only if you are doing a query operation in dynamodb. Its properties are populated here, it is set as the parameter ‘queryExprReference’ Because you are doing a scan operation, this value should not be set. If you expect your tables to be large, or be accessed frequently you will almost always want to be doing a query rather than a scan.

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