相关疑难解决方法(0)

DynamoDBMapper提供了从表中读取一个项目的不同方法:

• 询问
• 加载

是否有推荐,哪些可以使用？在快速测试中,以下两个代码段为具有主键= hash和range key = date的表返回相同的"MyEntry"项,而查询方法大约快10%.

加载

public MyEntry getEntryForDay(final Integer hash, final LocalDate date) {
    return mapper.load(MyEntry.class, hash, date);
}

询问

public MyEntry getEntryForDay(final Integer hash, final LocalDate date) {
    final MyEntry hashKeyValues = new MyEntry ();
    hashKeyValues.setHash(hash);
    final Condition rangeKeyCondition = new Condition()//
            .withComparisonOperator(ComparisonOperator.EQ.toString())//
            .withAttributeValueList(new AttributeValue().withS(new LocalDateMarshaller().marshall(date)));
    final DynamoDBQueryExpression<MyEntry> queryExpression = new DynamoDBQueryExpression<MyEntry>()//
            .withHashKeyValues(hashKeyValues)//
            .withRangeKeyCondition("date", rangeKeyCondition)//
            .withLimit(1);
    final List<MyEntry> storedEntries = mapper
            .query(MyEntry.class, queryExpression);
    if (storedEntries.size() == 0) {
        return null;
    }
    return storedEntries.get(0);
}