[hibernate-dev] Hibernate Search Projection

[Emmanuel Bernard]

On 18 mai 07, at 01:41, Max Rydahl Andersen wrote:

>> Projection
>
> What about .setCachedProjection  or .setIndexedProjection to  
> clearly signal
> it is not a "real" projection ?

But it *is* a real projection, just not from the database :-) The  
data is the same though
The API is in FullTextQuery.setProjection()
Do we need the redundancy?

>
>> Currently fields Store.NO or where the fieldbridge is one way are
>> ignored and return null.
>> The idea behind that is to be able to project across multiple
>> entities / index. Not sure if it's a useful feature.
>
> Shouldn't this result in an error ?! if the property is not  
> actually "mapped"
> shouldn't it fail ?

I couldn't make my mind.
My choice comes from the fact that Lucene is a totally unstructured  
data container.
For eg if you query
title:Hibernate summary:Rock
and if the documents don't have the summary field, it's silently  
ignored by lucene
It's kinda cool if you want to retrieve let's say Dvd and Book, some  
fields are shared and some are specific
But I will align with the majority here and better be strict first  
and relax later.

>
>> Custom query to load objects
>> You can define the Criteria query that will be use to load the
>> matching objects of a lucene query.
>> This is especially useful when an object graph (rather than an
>> object) is expected: you can refine the fetchMode.
>>
>> result = s.createFullTextQuery( query ).setCriteriaQuery(
>> 				s.createCriteria( Book.class ).setFetchMode( "authors",
>> FetchMode.JOIN )
>>                 ).list();
>>
>> will load the matching books and the associated authors.
>
> What happens if the query and the criteria are totally unrelated ?  
> And how are the link
> done between "query" and the Criteria ? you just add an in clause  
> on the "id" property "blindly" ?

It can't be, I read the Criteria entity root to filter the  
unstructured query
Yes I add an in clause (several actually, thanks Oracle) to the  
property marked as @DocumentId