[infinispan-dev] a dsl prototype for querying infinispan

[Sanne Grinovero]

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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