java embedded key-value data store for counters

Question

I am searching for an embedded key-value data store which

1. has Java API
2. easy to manipulate counters (aka SET value=value+10 WHERE key="k")
3. support multi-threads clients
4. High performance

I have found LevelDBJni , but it is designed for simple KV operation and unfriendly for counters. Are there better solutions?

Thanks.

Answer 1

With the Java library you can use a Map with an AtomicInteger as value.

In the following examples I use String as datatype for the key.

Eg

Map<String, AtomicInteger> kvStore = new ...

To manipulate the counters you can then use

kvStore.get("...").addAndGet(10);

To retrieve also the updated value

AtomicInteger value = kvStore.get("...").addAndGet(10);

As AtomicInteger is designed for concurrency a multi-threaded environmet should be no problem.

I cannot tell you how the performance of this is as I don't know your specific requirements so you have to determine this yourself.

Answer 2

嵌入式Java DB count-db（ https://github.com/koendeschacht/count-db ）在其API中提供了一个count方法，该方法应对此用例进行解答。

Answer 3

Take a look at http://www.mapdb.org . It is very high performance and offers a very familiar API (Java Map).