[hibernate-dev] JBoss Cache Searchable interfaces

[Manik Surtani]

Hi guys - a few comments on the public interfaces of SearchableCache -

1) IMO, I think that the SearchableCache.createQuery() method should  
*not* return a FullTextQuery, but instead a JBCS-specific CacheQuery  
interface with a subset of the methods in FullTextQuery.

I think the only methods in FullTextQuery that are relevant and that  
should be carried across to CacheQuery are:

* list()
* iterator();
* setFirstResult(int i);
* setMaxResults(int i);
* setFetchSize(int i);
* getResultSize();
* setSort();

I think all of the rest - such as filters, criteria and projections -  
are irrelevant to a query on a cache.  WDYT?  Emmanuel?

2) Also, rather than implement FullTextQuery.scroll() to return a  
ScrollableResults instance, I'd rather that iterator() returns an  
instance of a new interface, QueryResultsIterator, which extends  
j.u.ListIterator.  This gives us the ability to scroll back and forth  
over a result set, and we could add additional methods to jump to a  
specific point in the result set and helpers such as isLast(),  
isFirst(), isBeforeLast(), isAfterFirst(), first(), last(),  
afterFirst(), beforeLast().

I think that any benefit of a scrollable result set window preventing  
loading unnecessary objects from a DB are lost when your backing store  
is a cache and the objects are in memory anyway.  And besides, any  
further optimisations can be in the iterator implementation, such as  
just maintaining a list of CachedEntityIds (a composite of Fqn and  
key) and fetching the objects from the cache lazily, as required.

Also, with the above, 2, we don't leak any Hibernate or Hibernate  
Search interfaces into the user API which again IMO is a good thing.

Thoughts, comments?

Cheers
Manik




On 24 Jun 2008, at 11:47, Navin Surtani wrote:

>
>
> Begin forwarded message:
>
>> From: Emmanuel Bernard <emmanuel at hibernate.org>
>> Date: 24 June 2008 08:19:03 BST
>> To: Navin Surtani <navin at surtani.org>
>> Subject: Re: More hibernate questions
>>
>> Scroll is more important than iterate because it allows to read  
>> objects s a window and get rid of them on a regular basis without  
>> facing out of memory exception.
>> I think it's used more often than iterate
>>
>> On  Jun 23, 2008, at 18:17, Navin Surtani wrote:
>>
>>> Hey again -
>>>
>>> I have a CacheQueryImpl class that extends the FullTextQuery  
>>> interface and I am implementing the methods as similar as possible.
>>>
>>> A couple of problems occur when you are taking in and using  
>>> certain Hibernate objects for example. A problem lies with the  
>>> scroll() method. I think it is very similar to the iterate()  
>>> method and does not need to be implemented in CacheQueryImpl. Do  
>>> you know if Hibernate users generally use this method and find  
>>> that they need it? If so then I will try and implement it  
>>> otherwise then I will just make it throw an exception.
>>>
>>> Thanks again :)
>>> Navin.
>>
>

--
Manik Surtani
Lead, JBoss Cache
manik at jboss.org






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