快速查询表是否包含键（DynamoDB和Java）

问题描述

我有一个带有哈希和范围复杂键的表。

我可以使用Java版AWS开发工具包中的 GetItem 查询项目。
GetItem 如果找不到对象或作为 Map< String，AttributeValue> 。

我正在寻找最快的方法来检查对象是否存在

我在想也许提供 .withAttributesToGet ，例如：

I have a table with a hash and range complex key.
I can query an item using GetItem from AWS SDK for Java.The GetItem returns null if it doesn't find the object, or the item as a Map<String, AttributeValue>.
I am looking for the fastest approach to check whether the object does exist
I was thinking maybe supplying a .withAttributesToGet such as:

GetItemResult result =  dbClient.getItem(new GetItemRequest().
    withTableName(TABLE_NAME).
        withKey(new Key(new AttributeValue().withS(hashKey),
                        new AttributeValue().withS(rangeKey))).
        withAttributesToGet(new ArrayList<String>()));
Map<String, AttributeValue> item = result.getItem();
return (item != null);

另一种优化方法是不使用SDK JSON解析器，自己解析响应以快速检查项目已经返回。

Another optimization is to not use the SDK JSON parser and parse the response myself to quickly check if the item has returned.

谢谢

推荐答案

我认为在获取和检查它是否存在之间的速度差异可以忽略不计。您可以继续使用GetItem本身。如果该项目可能太大，则限制返回的属性。

I think there is negligible difference in speed between "getting" and checking if it exists. You can go ahead and use the GetItem itself. If the item is potentially too large, then limit the attributes being returned.

瓶颈在于到达Dynaamo DB服务器（REST API）的延迟以及从中获取数据。索引。因此，获取和检查将达到类似的速度。确保发出呼叫的服务器与Dynamo DB处于同一区域-这对速度有最大的影响。

The bottle neck is in latency to reach the Dynaamo DB servers (REST API) and in fetching from the index. So Getting and checking will be similar speed. Ensure that your server issuing the call is in the same region as Dynamo DB - This has max impact on the speed.

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