[infinispan-dev] a dsl prototype for querying infinispan

[Emmanuel Bernard]

Hehe yes http://emmanuelbernard.com/blog/2013/05/28/autocompletion-is-crap/

On 12 juin 2013, at 18:07, Sanne Grinovero <sanne at hibernate.org> wrote:

> wish: please try them in Eclipse too as sometimes the usage experience is not the same.
> 
> On 12 Jun 2013 18:05, "Emmanuel Bernard" <emmanuel at hibernate.org> wrote:
>> I forgot to say that fluent APIs in java are awesome but a nightmare to maintain backward compatibility wise. If you think building was hard, wait till you have to fix it or retrofit it.
>> 
>> That is also why thinking about all possible future needs is important.
>> 
>> Emmanuel
>> 
>> On 12 juin 2013, at 17:44, Emmanuel Bernard <emmanuel at hibernate.org> wrote:
>> 
>> > A few comments in no particular order
>> >
>> > - nice work
>> > - try and cover all future possible extensions of the language to be
>> >  sure you are not heading to a trap
>> > - no cross type support
>> >  I suspect some kind of Union query could be useful
>> >  (from(User.class)....union().from(Dog.class)...)
>> > - projection
>> >  you must think about projection and aggregation from day one even if
>> >  you end up not offering it initially.
>> > - I'm skeptical about contains* as I don't see much value in them as
>> >  they seem quite specific. Do they work beyond collection of native
>> >  types?
>> > - I can't see how you will write complex predicate compositions (nested
>> >  ands and ors) while keeping your elegant flow.
>> >  I suspect you need some external reference? From where?
>> >  That's usually where these styles of fluent APIs wo params fall
>> >  apart and why we went differently in JPA.
>> > - static method entry point
>> >  I suspect that using a static method entry point is a mistake.
>> >  Yes it looks simpler and more elegant than qb.from() but you also lose
>> >  any ability to have a context passed and used during the query
>> >  construction (like the CacheManager or whatever).
>> >  I could be wrong though as I haven't seen how you will execute the
>> >  query.
>> >
>> > Emmanuel
>> >
>> > On Fri 2013-06-07 18:56, Adrian Nistor wrote:
>> >> Hi all,
>> >>
>> >> As per ISPN-3169 "Define a Query API that will be common for library
>> >> mode + remote" we set out to define a simple dsl for writing queries
>> >> against embedded and remote caches that should be agnostic to the
>> >> actual engine that executes the query (lucene in our case now but
>> >> might be others later) and yet be easy to be translated into the
>> >> native query language of the said engine.
>> >>
>> >> Our dsl aims to support filtering cached entities:
>> >>  * by attributes allowing equality and range filters (less than,
>> >> greater than, between)
>> >>  * some very simple collections tests (contains(value),
>> >> containsAll(setOfValues), containsAny(setOfValues)) that can be
>> >> applied to attributes that are collections of values
>> >>  * string 'like' operator similar to SQL
>> >>  * 'in' filter, to test if the attribute value belongs to a given
>> >> fixed set of values
>> >>  * The filters can be composed of subfilters connected by logical
>> >> and/or operators. Operator precedence can be changed using nested
>> >> subfilters.
>> >>  * Negation is also allowed of course
>> >>  * besides filtering based on attributes of the root entity it
>> >> should also be able to filter on attributes of embedded entities
>> >> (eg. person.address.postalCode == "123") at any nesting level
>> >>
>> >> As for type safety, the dsl should not allow the user to build
>> >> syntactically invalid queries.
>> >> Having a dsl that is also typesafe with regard to the domain model
>> >> is desirable, but not a must for this early stage.
>> >>
>> >> Here is a simple domain model I've used for writing some sample queries.
>> >>
>> >>   // a typesafe version User $user = $(User.class);
>> >>   Query q0 = from($user)
>> >>   .having($user.getName()).eq("John")
>> >>   .and()
>> >>   .having($user.getAddress().getPostCode()).eq("NW123")
>> >>   .build(); // non typesafe field references
>> >>   Query q1 = from(User.class)
>> >>   .having("name").eq("John")
>> >>   .and()
>> >>   .having("surname").eq("Doe")
>> >>   .build(); More query samples on github here:
>> >>   https://github.com/anistor/infinispan/blob/t_3169_m/query/src/main/java/org/infinispan/query/sandbox/sample_domain_model/QuerySamples.java
>> >>   This is just an interface sketch, not an implementation. Your
>> >>   thoughts and comments regarding this dsl are very welcome! I'll add
>> >>   all of the above to the wiki too. Cheers
>> >
>> >> _______________________________________________
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>> >
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