it is new in NH3.2

2011/3/26 José F. Romaniello <[email protected]>

> wow! didn't know about <subselect /> ... I learn something new about NH
> every day :)
>
>
> 2011/3/26 Fabio Maulo <[email protected]>
>
>>   <class name="Blog" mutable="false">
>>     <subselect>
>>       SELECT Blog.Id, Blog.Author, Blog.Title, Comment.Comment
>>       FROM Blog INNER JOIN Comment ON Blog.Id = Comment.Blog_id
>>       WHERE Comment.LanguageId = :blogcomment.languageId
>>     </subselect>
>>     <id name="Id">
>>       <generator class="assigned" />
>>     </id>
>>     <property name="Author" />
>>     <property name="Title" />
>>     <property name="Comment" />
>>   </class>
>>
>>   <filter-def name="blogcomment">
>>     <filter-param name="languageId" type="int"/>
>>   </filter-def>
>>
>>
>> 2011/3/25 Krzysztof Koźmic <[email protected]>
>>
>>> So I have a one-to-many tables in database that looks like the following
>>> (I'm on NHibernate 3.1):
>>>
>>> blog
>>>    id
>>>    title
>>>    author
>>>
>>> comments
>>>    id
>>>    blog_Id
>>>    languageid
>>>    comment
>>>
>>> and I want to map it to a *single* class with *single* comment property
>>> that maps to text column in comments table for current language.
>>>
>>> Basically the idea is identical to one ayende had few years back:
>>> http://ayende.com/Blog/archive/2006/12/26/localizingnhibernatecontextualparameters.aspx
>>>
>>> The difference is I try to accomplish this without subselect but using
>>> <join /> instead (mostly because the table with translations has more
>>> columns than just the text that I may need to include in my joined class).
>>>
>>> So I created a solution for that and I'm also using filter to pass
>>> language id to queries. I also have a noop property in my mapping for the
>>> languageid as well as where clause in my mapping that does the filtering.
>>>
>>> And here's the SQL that NHibernate generates:
>>>
>>> SELECT this_.Id           as Id0_0_,
>>>       this_.Author       as Author0_0_,
>>>       this_.Title        as Title0_0_,
>>>       this_1_.Comment    as Comment1_0_,
>>>       this_1_.LanguageId as LanguageId1_0_
>>> FROM   Blog this_
>>>       inner join Comment this_1_
>>>         on this_.Id = this_1_.Blog_id
>>> WHERE  (this_.LanguageId = 2 /* @p0 */)
>>>
>>> The SQL is invalid as the where should be on this_1_.LanguageId as the
>>> value comes from the joined table, not the main one.
>>>
>>> Also the LanguageId column is mapped as access="noop" which TTBOMK should
>>> mean it won't be queried for so I'm surprised to see NHibernate is trying to
>>> select it as well. To me it is just wasting bandwith.
>>>
>>> So I have two questions now.
>>>
>>> 1. How can I accomplish what I'm trying to get to.
>>> 2. Are those issues I mentioned (invalid where clause and ignoring noop
>>> access) bugs in NHibernate or am I looking at it from the wrong angle?
>>>
>>> Reproduction demo app (along with database dump) available here if
>>> someone wants to play with it: http://ge.tt/5xoiqYY
>>>
>>> cheers,
>>> Krzysztof
>>>
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>>>
>>
>>
>> --
>> Fabio Maulo
>>
>>
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-- 
Fabio Maulo

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