使用dynamodb映射器将属性投影到索引

Question

I just can't find the way to project selected attributes (not hashkey) into indices using dynamodb mapper annotations.

Consider an example:

@DynamoDBTable(tableName = "scores")
public class DynaScoreItem {
    @DynamoDBHashKey
    int user;
    @DynamoDBRangeKey
    int level;
    @DynamoDBAttribute
    int score;
    @DynamoDBIndexRangeKey(localSecondaryIndexName = "sort_by_added")
    long added;
}

I just want to add score to "sort_by_added" index. How to do it using annotations?

Answer 1

Attribute projections are set on index creation, and not determined by annotations (currently). There is no way to mark attributes as part of an attribute projection with annotations. Looking at the Javadoc for the DynamoDBMapper.generateCreateTableRequest(Class<?> clazz) :

Parse the given POJO class and return the CreateTableRequest for the DynamoDB table it represents. Note that the returned request does not include the required ProvisionedThroughput parameters for the primary table and the GSIs, and that all secondary indexes are initialized with the default projection type - KEY_ONLY.

The key part of this is the default projection type - KEY_ONLY . If you create your table using this API, you would have to specify the projections yourself.