[hibernate-issues] [Hibernate-JIRA] Commented: (HHH-2101) Can't use outer join in table with composite-id, key-many-to-one
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http://opensource.atlassian.com/projects/hibernate/browse/HHH-2101?page=c...
]
Hugo Zhu commented on HHH-2101:
-------------------------------
Just found "select this from BlogUserUrl this inner join fetch this.url where
this.blog=?" is a much better way.
Hugo
Can't use outer join in table with composite-id, key-many-to-one
----------------------------------------------------------------
Key: HHH-2101
URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-2101
Project: Hibernate3
Type: Improvement
Components: core
Versions: 3.1.3
Environment: MYSQL: 5.0.15-nt-log
mysql-connector-java-3.0.16-ga
Hibernate 3.1.3
Reporter: Hugo Zhu
MYSQL 5 database;
HBM like below:
<class name="Blog" table="blog"
dynamic-update="true">
<id column="id" name="id" type="long">
<generator class="native"/>
</id>
...
</class>
<class name="BlogUrl" table="blog_url"
dynamic-update="true">
<id column="id" name="id" type="long">
<generator class="native"/>
</id>
<property name="url" type="string" length="255"
not-null="true"/>
<property name="urlHash" type="string"
length="32" unique="true" not-null="true"/>
<property name="numOfHits" type="integer"/>
<property name="created" type="timestamp"/>
</class>
<class name="BlogUserUrl" table="blog_user_url"
dynamic-update="true">
<composite-id>
<key-many-to-one name="url" class="BlogUrl"/>
<key-many-to-one name="blog" class="Blog"/>
</composite-id>
<property name="title" type="string"
length="255" not-null="true"/>
<property name="description" type="string"
length="255"/>
<property name="created" type="timestamp"/>
</class>
But:
getSession().createCriteria(BlogUserUrl.class).setFetchMode("url",FetchMode.JOIN).add(Restrictions.eq("blog",
blog).setMaxResults(25).list();
Still generates 2 queries - query 1: query out BlogUserUrl, then query 2: possible 25 sub
queries for earch BlogUrl
The better way should be just 1 outer join.
I have set: <property name="max_fetch_depth">1</property> in
Hibernate configuration, but there is no join attribute in element: key-many-to-one.
The only way to solve this issue I can find out is:
HQL: select this,this.url from BlogUserUrl this where this.blog=?, but I have to add a
loop in results to conver the Object[] list to BlogUserUrl only list. Not ideal
Thanks for looking into this issue.
Hugo
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