如何在HashKey和range Key的基础上在DynamoDB中进行查询？

Question

我是新手DynamoDb.我只想知道如何使用hashKey和查询DynamoDB中的表rangeKey.

假设我的表是TestTable,它的架构是这样的:

1.Id (HK of type String)
2 Date (RK of type String )
3 Name (attribute of type String)

现在,如果我想在此基础上对这个表查询hashKey是Id在这里,我们做出query如下:

假设我的查询是让所有项目都有 Id ="123".

TestTable testTable = new TestTable();
testTable.setId("123");

DynamoDBQueryExpression<TestTable> queryExpression = new DynamoDBQueryExpression<TestTable>()
                                                                .withHashKeyValues(TestTable)
                                                                .withConsistentRead(false);

现在我想得到所有物品Id ="123" and Date ="1234".

我怎么能查询这个东西 DynamoDB

我正在使用java我的编程语言.

Answer 1

我前段时间使用AWS Java SDK编写了一篇关于DynamoDB查询和索引的文章:http://labs.journwe.com/2013/12/15/dynamodb-secondary-indexes/

在您的情况下,它应该像这样工作(请参阅http://docs.aws.amazon.com/amazondynamodb/latest/developerguide/JavaQueryScanORMModelExample.html):

AmazonDynamoDBClient client = new AmazonDynamoDBClient(new ProfileCredentialsProvider());
DynamoDBMapper mapper = new DynamoDBMapper(client);

String hashKey = "123";
long twoWeeksAgoMilli = (new Date()).getTime() - (15L*24L*60L*60L*1000L);
Date twoWeeksAgo = new Date();
twoWeeksAgo.setTime(twoWeeksAgoMilli);
SimpleDateFormat dateFormatter = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSS'Z'");
dateFormatter.setTimeZone(TimeZone.getTimeZone("UTC"));
String twoWeeksAgoStr = dateFormatter.format(twoWeeksAgo);            
Condition rangeKeyCondition = new Condition()
        .withComparisonOperator(ComparisonOperator.GT.toString())
        .withAttributeValueList(new AttributeValue().withS(twoWeeksAgoStr.toString()));

Reply replyKey = new Reply();
replyKey.setId(hashKey);

DynamoDBQueryExpression<Reply> queryExpression = new DynamoDBQueryExpression<Reply>()
        .withHashKeyValues(replyKey)
        .withRangeKeyCondition("ReplyDateTime", rangeKeyCondition);

List<Reply> latestReplies = mapper.query(Reply.class, queryExpression);

有关详细信息,请查看DynamoDB文档的Java Object Persistence Model部分.

Answer 2

你可以使用dynamoDbMapper.load()如下:

TestTable testTable = new TestTable();
testTable.setId("123");
testTable.setDate("1234");
TestTable result = dynamoDBMapper.load(testTable);