[infinispan-dev] Design change in Infinispan Query

[Emmanuel Bernard]

On 25 Feb 2014, at 16:08, Mircea Markus <mmarkus at redhat.com> wrote:

> 
> On Feb 25, 2014, at 9:28 AM, Emmanuel Bernard <emmanuel at hibernate.org> wrote:
> 
>>> On 24 févr. 2014, at 17:39, Mircea Markus <mmarkus at redhat.com> wrote:
>>> 
>>> 
>>>> On Feb 17, 2014, at 10:13 PM, Emmanuel Bernard <emmanuel at hibernate.org> wrote:
>>>> 
>>>> By the way, Mircea, Sanne and I had quite a long discussion about this one and the idea of one cache per entity. It turns out that the right (as in easy) solution does involve a higher level programming model like OGM provides. You can simulate it yourself using the Infinispan APIs but it is just cumbersome.
>>> 
>>> Curious to hear the whole story :-)
>>> We cannot mandate all the suers to use OGM though, one of the reasons being OGM is not platform independent (hotrod). 
>> 
>> Then solve all the issues I have raised with a magic wand and come back to me when you have done it, I'm interested.
> 
> People are going to use infinispan with one cache per entity, because it makes sense:
> - different config (repl/dist | persistent/non-persistent) for different data types
> - have map/reduce tasks running only the Person entires not on Dog as well, when you want to select (Person) where age > 18
> I don't see a reason to forbid this, on the contrary. The way I see it the relation between (OGM, ISPN) <=> (Hibernate, JDBC). Indeed OGM would be a better abstraction and should be recommended as such for the Java clients, but ultimately we're a general purpose storage engine that is available to different platforms as well.
> 

I do disagree on your assessment.
I did write a whole essay on why I think your view is problematic - I was getting tired of repeating myself ;P
https://github.com/infinispan/infinispan/wiki/A-continuum-of-data-structure-and-query-complexity

To anecdotally answer your specific example, yes different configs for different entities is an interesting benefit but it has to outweigh the drawbacks.
If you have to do a map reduce for tasks so simple as age > 18, I think you system better have to be prepared to run gazillions of M/R jobs.
I think that Dogs and any domestic animal is fundamentally related to humans - Person in your case. So queries involving both will be required - a cross cache M/R is not doable today AFAIK and even if it was, it’s still M/R and all its drawbacks.

To me, the Cache API and Hot Rod are well suited for what I call self contained object graph (i.e. where Dog would be an embedded object of Person and not a separate Entity). In that situation, there is a single cache.
One cache per entity does make sense for API that do support what I call connected entities. Hibernate OGM specifically.
But please read the wiki page first before commenting. I did spend a lot of time on it
https://github.com/infinispan/infinispan/wiki/A-continuum-of-data-structure-and-query-complexity

Emmanuel