Re: [infinispan-dev] Design change in Infinispan Query

On Feb 26, 2014, at 5:14 PM, Emmanuel Bernard <emmanuel(a)hibernate.org&gt; wrote: Thanks for writing this up, it is a good taxonomy of data storage schemes and querying. Using a single cache for all the types is practical at all :-) Just to expand my idea, people prefer using different caches for many reasons: - security: Account cache has a different security requirements than the News cache - data consistency: News is a non-transactional cache, Account require pessimistic XA transactions - expiry: expire last year's news from the system. Not the same for Accounts - availability: I want the Accounts cache to be backed up to another site. I don't want that for the News cache - logical data grouping: mixing Accounts with News doesn't make sense. I might want to know which account appeared in the news, though. I want to run a simple M/R job in the evening to determine who turns 18 tomorrow, to congratulate them. Once a day, not gazzilions of times, and I don't need to index the age filed just for that. Also when it comes to Map/Reduce, the drawback of holding all the data in a single cache is two-folded: - performance: you iterate over the data that is not related to your query. - programming model: the Map/Reduce implementation has a dependency on both Dog and Person. If I add Cats to the cache, I'll need to update the M/R code to be aware of that as well. Same if I rename/remove Dog. Not nice. I see where you come from but I don't think requiring people to use a single cache for all the entities is an option. Besides a natural logical separation, different data has different storage requirements: security, access patterns, consistency, durability, availability etc. For most of the non-trivial use cases, using a single cache just wont do. OGM does a great job covering this, but it is very specific: java only and OOP - our C/S mode, hotrod specifically, is language independent and not OOP. Also I would like to comment on the following statements: "I believe a cache API and Hot Rod are well suited to address up to the self contained object graph use case with a couple of relations maintained manually by the application but that cannot be queried. For the connected entities use case, only a high level paradigm is suited like JPA." I don't think storing object graphs should be under scrutiny here: Infinispan C/S mode (and there's where most of the client focus is BTW) has a schema (prtobuf) that does not support object graphs. I also think expecting people to use multiple caches for multiple data types is a solid assumption to start from. And here's me speculating: these data types have logical relations between them so people will ask for querying. In order to queries on multiple data types, you can either merge them together (your suggestion) or support some sort of new cross-cache indexing/querying/api. x-cache querying is more flexible and less restraining than merging data, but from what I understand from you has certain implementation challenges. There's no pressure to take a decision now around supporting queries spreading multiple caches - just something to keep an eye on when dealing with use cases/users. ATM merging data is the only solution available, let's wait and see if people ask for more. I do read your comments and I really appreciate your feedback. We come from slightly different worlds and look at things from different angles, but discussions like this raise many good points. Cheers, -- Mircea Markus Infinispan lead (www.infinispan.org)