通过Java中的主键列表查找cassandra [英] cassandra lookup by list of primary keys in java

问题描述

我正在实现一项功能，要求通过主键列表查找Cassandra。

I am implementing a feature which requires looking up Cassandra by a list of primary keys.

下面是一个示例数据，其中id是主键

Below is an example data where id is primary key

mytable
id          column1
1           423
2           542
3           678
4           45534
5           435634
6           2435
7           678
8           4564
9           546

我大多数人通过ID查询查询，但在某些特殊情况下，我想获取ID列表的数据。
我当前正在做的事情如下：

Most of my queries a lookup by id, but for some special cases I would like to get data for a list of ids. The way I am currently doing is a follows:

public Object fetchFromCassandraForId(int id);

int ids[] = {1, 3, 5, 7, 9};
List<Object> results;
for(int id: ids) {
  results.add(fetchFromCassandraForId(id));
}

这导致向cassandra发出多个网络调用，是否有可能以某种方式进行批处理，因此我想知道cassandra是否支持通过ID列表进行快速查找

This results in issuing multiple network call to cassandra, Is it possible to batch this somehow, therefore i would like to know if cassandra supports fast lookup by list of ids

select coulmn1 from mytable where id in (1, 3, 5, 7, 9);

？
任何帮助或指针将不胜感激？

? Any help or pointers would be appreciated?

推荐答案

如果 id 是完整的主键，然后Cassandra支持这一点，尽管从性能的角度上不建议这样做：

If the id is the full primary key, then Cassandra supports this, although it's not recommended from performance point of view:

• 请求发送到协调节点

• request is sent to coordinator node
• coordinator node finds a replica for each of the id, and send individual request to them
• wait for results from every node, collect them to result set & send back

结果：

• 所有子查询都需要等待对于最慢的副本


• 您还有一个从协调器到副本的网络希望


• 您需要对协调器节点施加更大的压力，因为它需要保持导致内存中出现

如果您对每个 id 进行大量并行，异步请求来自应用程序的值，则您：

If you do a lot of parallel, asynchronous requests for each of the id values from application, then you:

• 避免额外的跃点-如果您使用带有令牌感知负载平衡的准备好的语句，那么查询将直接发送到副本


• 您可能会在获取结果时开始处理结果，而不是等待所有事情

因此发送并行异步请求可能比使用 IN ...

So sending parallel asynchronous requests could be faster than sending one request with IN...

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