title: DynamoDBMappingException no HASH key for GSI
body: <p>This error that Dynamo throws is extremely vague but there is a way to narrow down the issue quickly. The code that throws this error can be found at <a href="https://github.com/aws/aws-sdk-java/blob/master/aws-java-sdk-dynamodb/src/main/java/com/amazonaws/services/dynamodbv2/datamodeling/DynamoDBMapperTableModel.java" rel="nofollow noreferrer">https://github.com/aws/aws-sdk-java/blob/master/aws-java-sdk-dynamodb/src/main/java/com/amazonaws/services/dynamodbv2/datamodeling/DynamoDBMapperTableModel.java</a> </p>
  
  <p>Which is currently the only google search result for "no HASH key for GSI" which is why I've been inspired to create this post.</p>