[hibernate-dev] HSearch Projection queries & multiple fields with same name

[Ales Justin]

>>>> I think anything handled by not-Lucene is wrong.
>>> 
>>> I'm afraid Lucene won't do it, so we have no option. It's definitely
>>> not designed to do this: even a custom Collector can't return more
>>> results than Documents in its segment, as all representations work by
>>> using int as relative ids.
>> 
>> Even if we have Document(s) for every possible combination - all elements of cartesian product?
>> Where current impl basically handles 1 x 1 x 1 x ... x 1.
>> And new HS impl just needs to take this multi Document approach into account.
> 
> The problem with this approach is that it will makes things hard for
> most usecase except the one involving associated collections.
> We would need to filter out documents that refer to the same entity
> unless the query ought to be a cartesian one.
> this seems like a wrong thing to do as it would cost us more index size
> and speed as well as make the overall code more complex.
> I'd rather have a transformer cartesianize the end result. That would be
> much cheaper and code localized.

But this way you only know the real size once you expand the results into cartesian results.
Which, as we discussed, completely beaks any counters and possible lazy handling.
Not to mention you do this in-memory, which brings additional problems.