[hibernate-dev] Process and requirements for contributing to Hibernate & feature proposal

[Marcin Mościcki]

Hi,

Some time ago I submitted a minor bug having to do with named sql query
mapping/binding (
http://opensource.atlassian.com/projects/hibernate/browse/HHH-3108) and
subsequently fixed it. Hibernate page mentions that contributions should be
submitted in patch format, but doesn't say to what version / svn tag - I
presume last stable one, that is 3.2.6.ga?

As I already spent some time debugging and got a basic understanding of the
code, I thought I might add some functionality I heavily miss. The question
is, is it possible for such a user contribution to make it to be
incorporated into the code? If so, what would be the procedure and
requirements?

My issues with hibernate I'd like to improve concern efficiency and control
of fetching whole graphs of objects with many associations:

1. First of all, a possibility of specifying a custom collection loader for
fetch='subselect' on a per-query basis. The root query would be able to
define a subselect query used to fetch collections owned by returned
entities (ideally also nested associations). If original query is
complicated (involves joins or subselects), current solution is highly
ineffective and I found I could often write optimized queries returning the
same data. This is especially pronounced when a large percentage of total
data in the table is returned by associated queries.

2. Do some automatic optimization for fetch="subselect". Most notable
example is fetching collections defined in subclasses of an entity returned
by a polymorphic query. When using table-per-concrete-subclass approach,
first query results in an SQL with a couple of joins, and is then used
literally as a subselect in the query for associated objects. In most cases
it would be sufficient to do the subselect only against the base class
table.

3. Allow to use HQL queries as collection loaders, not only SQL queries. I
don't know, maybe you're currently working on it - it seems so natural and
I've seen a feature request in JIRA.

If you'd be interested in such improvements and find them compatible with
the project's roadmap, please let me know. I am very enthusiastic about
seeing them in hibernate - the lack of 1) pushed us to drop hibernate for a
more flexible, low-level solution in some projects having a complicated
object model (arguably exactly those which would really benefit from a
model-driven persistance approach). Unfortunately, there's no way my company
would allow usage of an in-house patched version of hibernate, so my work on
such a patch would be mostly a waste of time if it didn't make it to a
release one day.

Best regards,

-- 
c):-i Marcin Mościcki
---------------------------------------------------------------------------------------------------
It is, as far as he knows, the only way of coming downstairs,
but sometimes he feels that there really is another way,
if only he could stop bumping for a moment and think of it.
And then he feels that perhaps there isn't.
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