CODEWITHSUNDEEP
hazelcast
KIC
KIC

Reputation: 6121

Defining a Hazelcast MapStore for Key-Ranges

When we want to implement the MapStore interface we only have the method loadAll for initializing the map. Therefore you have to provide a set of keys to load into the map. How do you handle the situation when you have date / time as primary key. Intuitively one would define a key range where tst between a and b. But since we only can provide a Set we have to pre-fetch all the possible date-time values (via SQL or whatever). And the next time the IMap will start to hammer the database fetching every key one by one. Is this the best approach? Isn't there a more convenient way to do this?

Upvotes: 0

Views: 647

Answers (1)

Juan José Vázquez Delgado
Juan José Vázquez Delgado

Reputation: 121

My advice would be to stop thinking about the maps as if they were tables in a relational database. Try to think in terms that conform to the semantics of a Map (if you are using a Map as there are other distributed collections in Hazelcast). For example, you have to keep in mind that you can only make queries about objects that are available in memory as the semantics of query applies only to the case in which Hazelcast is used as a data grid and not as a cache. If semantics is the use of a cache, you should limit your access by key, as you would proceed with a traditional map in Java.

For example, when it comes to a data grid, you must think that access to the database will occur typically only to respond to disaster recovery scenarios. Therefore, the initial data loading from disk to memory may strongly hit the database, but that would only occur in cases of recovery, so that it is not such a major handicap. In the case of use of caching, yes it would be important to be very efficient when planning your persistence strategy since access to the database will be more frequent.

If you provide further information about what it's your particular use case, especially regarding eviction policies, maybe I might help you more.

Hope this helps.

Upvotes: 3

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