Hi,
I'm looking at the EntityFinder, both on its own, and in relation to
querying of data in general. We have talked about that sometimes one
would want to do queries over other things than just entities, such as
iterables and events, and a question is whether it is possible to tweak
the EntityFinder to handle that as well.
AFAICT the main thing to change would be to rename it to just "Finder",
and change so that the returned type ("EntityReference") becomes a
generic type, so that it can be e.g. "EntityReference" or "Value" or
"DomainEvent" etc. The methods and exceptions would also be renamed
accordingly so that they are not entity specific.
Then, for entities one would extend "Finder<EntityReference>" and for
searching the event-store it would be "Finder<DomainEvent>" (or somesuch).
The last question is how to specify the dataset to apply a query to.
Today we do queryBuilder.newQuery(uow) and
queryBuilder.newQuery(Iterable). If the Finder concept is a bit more
generic it would make more sense to do it the other way round, i.e.
uow.newQuery(queryBuilder), and
Iterables.newQuery(iterable,queryBuilder), or something like that. Then
we could add a EventFinder.newQuery(queryBuilder) quite easily, as well
as other services that are capable of searching. The Query concept is
then not limited to entities at all, but is mostly just a convenient way
to build and handle queries, regardless of target. This is especially
true with the new API that allows custom operators.
One thing that is important in non-Qi4j settings is that the query can
actually return data straight, rather than having to go through entities
to load data. It would be possible to allow this by doing:
queryBuilderFactory.newQueryBuilder(SomeValue.class)
where the properties of SomeValue essentially dictate the list of
"columns" that you want to receive. The value itself becomes the
projection, but strongly typed. That could be incredibly efficient.
These are just some ideas on how to improve the Query API. Any
thoughts/suggestions on this?
/Rickard
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