Is there a multi-valued keystore?

Question

Is there a specialized storage for storing tuples, i.e. t = (clicks, impressions, ctr) hashed by several values ​​- say, pageId, categoryId, userId, sessionId et cetera.

I know I can do this using MySQL, MongoDb and so on. But I'm more looking for a specialized and mabye even built-in (in Java) store. It should not offer a complex query language or transaction such as RDMBS. But atomicity and durability would be pro .;)

I believe this may also be useful for applications like DWH that store aggregated data in multiple dimensions, but I have not found such a product.

Answer 1

Your best bet - either use

HashMap<Key1Type, HashMap<Key2Type, ValueType>> 

or if your objects can be represented via a string, you can combine their values ​​and save them all in

HashMap<string, ValueType>

Answer 2

If you can live with a periodic boot process, an OLAP server such as Mondrian or SQL Server Analysis Services may work for you. They do just such things, although the underlying data structure is not a hash table. In practice, you will need to generate data in the database and load the data from the database into the cube.

Answer 3

, . wiredtiger .

Key composition is the principle of packing multiple values ​​in one value. The simplest composition uses char as a delimiter, such as ":".