快速查询包含键的表（DynamoDB 和 Java）
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Quickly query a table if it contains a key (DynamoDB and Java)
提问by Chen Harel
I have a table with a hash and range complex key.
I can query an item using GetItemfrom AWS SDK for Java.
The GetItemreturns 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 .withAttributesToGetsuch as:
我有一个带有哈希和范围复杂键的表。
我可以使用GetItemAWS SDK for Java查询项目。将GetItem返回null如果没有找到对象，或作为项目Map<String, AttributeValue>。
我正在寻找检查对象是否确实存在的最快方法，
我想可能会提供.withAttributesToGet诸如：
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);
Another optimization is to not use the SDK JSON parser and parse the response myself to quickly check if the item has returned.
另一个优化是不使用 SDK JSON 解析器并自己解析响应以快速检查项目是否已返回。
Thanks
谢谢
采纳答案by Sony Kadavan
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.
我认为“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。如果项目可能太大，则限制返回的属性。
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.
瓶颈在于到达 Dynaamo 数据库服务器 (REST API) 和从索引中获取的延迟。所以获取和检查将是相似的速度。确保发出调用的服务器与 Dynamo DB 位于同一区域 - 这对速度影响最大。
回答by Ashwin Patti
By mentioning only the hash key as attributes to get, you could have better performance and don't waste your throughput.
通过仅提及哈希键作为要获取的属性，您可以获得更好的性能并且不会浪费您的吞吐量。
