NHibernate QueryOver - 结果太多的集合 [英] NHibernate QueryOver - collection with too many results

问题描述

尊敬的 NHibernate 用户:

Dear NHibernate users,

我已经尝试、阅读和诸如此类的东西已经 2 天了，但仍然无法解决这个问题，尽管我认为使用 QueryOver API 是一件容易的事.

I've been trying, reading and whatnot for 2 days now, but still can't figure this out, even though I presumed it to be an easy task with QueryOver API.

这是我的两个实体:

ATTRIBUTE
---------------------------
public int Id { get; set; }
public int LanguageId { get; set; }
public string Title { get; set; }
public IList<Option> Options { get; set; }


OPTION
---------------------------
public int Id { get; set; }
public Attribute Attribute { get; set; }
public int LanguageId { get; set; }
public string Title { get; set; }

映射如下:

<class name="Attribute" lazy="false" table="attribute" dynamic-insert="true" dynamic-update="true" select-before-update="true">
    <id name="Id" column="attribute_id" type="System.Int32">
        <generator class="native"/>
    </id>

    <bag name="Options" lazy="false" cascade="all">
        <key column="attribute_id" not-null="true" />
        <one-to-many class="Option" not-found="ignore" />
    </bag>

    <join table="attribute_i18n" inverse="true" fetch="join">
        <key column="attribute_id" not-null="true"/>
        <property name="LanguageId" column="language_id" type="System.Int32" not-null="true" />
        <property name="Title" column="title" type="System.String" length="255" not-null="true" />
    </join>
</class>

<class name="Option" lazy="false" table="options" dynamic-insert="true" dynamic-update="true" select-before-update="true">
    <id name="Id" column="option_id" type="System.Int32">
        <generator class="native"/>
    </id>

    <many-to-one name="Attribute" class="Attribute" column="attribute_id" not-null="true" />

    <join table="option_i18n" inverse="true" fetch="join">
        <key column="option_id" not-null="true"/>
        <property name="LanguageId" column="language_id" type="System.Int32" not-null="true" />
        <property name="Title" column="title" type="System.String" length="255" not-null="true" />
    </join>
</class>

请注意，两个表都连接到自己的i18n"表(支持多语言条目)，并引用其 language_id 列.

Note that both tables join towards its own "i18n"-table (support of multilingual entries), and refer to its language_id column.

此外，我尝试使用 QueryOver API，并在 LanguageId 设置为 1 的情况下查询 Options-property 的那些选项.

Furthermore, I try to use the QueryOver API, and query the Options-property for those options with LanguageId set to 1.

拉了很多头发后，我的查询又回到了我开始的地方:

After a lot of hair pulling, my query is back to what I started with:

Attribute attribute = null;
Option option = null;

result = Session.QueryOver(() => attribute)
                .Where(() => attribute.LanguageId == 1)
                .Left.JoinAlias(i => i.Options, () => option)
                .Where(() => option.LanguageId == 1)
                .TransformUsing(Transformers.DistinctRootEntity)
                .List();

所以，对于我的问题:这个查询一直在我的选项列表中给我一组双选项(对于 language_id 1 和 2).我只想选择 language_id = 1，但令我沮丧的是 API 不理解我(..或者相反?).

So, to my problem: This query keeps on giving me a double set of options in my option list (for language_id 1 and 2). I want to select only language_id = 1, but to my frustration the API doesn't understand me (..or was it the other way around?).

非常感谢有关如何使我的查询与我的 OPTION 包集合相匹配的任何帮助！:-) 谢谢！

Any help on how to make my query work against my bag-collection of OPTIONs is greatly appreciated! :-) Thanks!

米卡尔

推荐答案

我担心，他不会工作.根据 的设计和性质.如文档中所述:

I am afraid, that his won't work. By design and the nature of the <join>. As stated in the documentation:

5.1.19.加入

使用 元素，可以将一个类的属性映射到多个表，当表之间存在 1 对 1 关系.

Using the <join> element, it is possible to map properties of one class to several tables, when there's a 1-to-1 relationship between the tables.

如何(我愿意)解决这个问题的方式有点不同.我有一个对象 Language，Option 有语言的集合

The way how to (I do) solve this issue is a bit different. I have an object Language, the Option has colleciton of languages

public virtual IList<Language> Languages {get; set;}

映射例如

<bag name="Languages"  batch-size="25"
  cascade="all-delete-orphan" inverse="true" >
  <key column="option_id" />
  <one-to-many class="Language" />

  <filter name="LanguagFilter" condition=":languageId = LanguageId" />
</bag>

诀窍在于过滤器.这是 where 映射属性(18.1. NHibernate 过滤器)

The trick is in the filter. This is a dynamic version of the where mapping-attribute (18.1. NHibernate filters)

<filter-def name="LanguageFilter" >
  <filter-param name="languageId" type="Int32" />
</filter-def>

然后，我们可以为当前会话的所有操作打开过滤器.每个请求(如果是 Web 应用程序)只有一次，在某个 AOP 中，我们知道语言 ID:

Then, we can turn the filter on, for all operations of the current session. Only once per request (if web app), inside some AOP, where we know the language id:

var filter = session.EnableFilter("LanguageFilter");
filter.SetParameter("languageId", theCurrentLanguageIdFromUser);

最后，我们知道，Languages 集合只包含一条记录，我们总是可以访问 .First().更多语言不再有多重结果

And finally, we know, that the collection Languages contains only one record and we can always access .First(). No more multiple results with more languages

另见:https://stackoverflow.com/a/16625867/1679310、https://stackoverflow.com/a/18479266/1679310

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