Hi,

When I debug a open source project, I found that the underlying hibernate works weirdly: A simple query will cause related tables rows be deleted and re-inserted.
Maybe this behavior is to keep data in memory and database synchronized?
But this behavior will cause performance problem and unexpected result, I think.
Can anyone give some hints to avoid the unnecessary delete/insert?

Thanks,
Xiong

Hibernate version:3.1.3

Mapping documents:
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping>

<class name="org.blojsom.blog.database.DatabaseBlog" table="Blog" lazy="false">


<id name="id">
<column name="id" sql-type="integer" not-null="true" unique="true"/>
<generator class="identity"/>
</id>

<property name="blogId">
<column name="blog_id" sql-type="string" not-null="true" unique="true"/>
</property>

<map name="templates" table="Template" cascade="all" inverse="false" lazy="false">
<key column="blog_id" not-null="true"/>
<map-key column="template_flavor" type="string"/>
<element column="template_value" type="string"/>
</map>

<map name="plugins" table="Plugin" cascade="all" inverse="false" lazy="false">
<key column="blog_id" not-null="true"/>
<map-key column="plugin_flavor" type="string"/>
<element column="plugin_value" type="string"/>
</map>

<map name="properties" table="Properties" cascade="all" inverse="false" lazy="false">
<key column="blog_id" not-null="true"/>
<map-key column="property_name" type="string"/>
<element column="property_value" type="text"/>
</map>

</class>

<sql-query name="blog.id.list">
select blog_id from Blog
</sql-query>

</hibernate-mapping>

CREATE TABLE `Plugin` (
`blog_id` int(11) NOT NULL,
`plugin_flavor` varchar(50) NOT NULL,
`plugin_value` varchar(4096) default NULL,
`plugin_id` int(11) NOT NULL auto_increment,
PRIMARY KEY(`plugin_id`),
KEY `plugin_blog_blogidfk` (`blog_id`),
CONSTRAINT `plugin_blog_blogidfk` FOREIGN KEY (`blog_id`) REFERENCES `Blog` (`id`) ON DELETE CASCADE
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

CREATE TABLE `Properties` (
`blog_id` int(11) NOT NULL,
`property_name` varchar(255) NOT NULL,
`property_value` longtext,
`property_id` int(11) NOT NULL auto_increment,
PRIMARY KEY(`property_id`),
KEY `properties_blog_blogidfk` (`blog_id`),
CONSTRAINT `properties_blog_blogidfk` FOREIGN KEY (`blog_id`) REFERENCES `Blog` (`id`) ON DELETE CASCADE
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

CREATE TABLE `Template` (
`blog_id` int(11) NOT NULL,
`template_flavor` varchar(50) NOT NULL,
`template_value` varchar(255) default NULL,
`template_id` int(11) NOT NULL auto_increment,
PRIMARY KEY(`template_id`),
KEY `template_blog_blogidfk` (`blog_id`),
CONSTRAINT `template_blog_blogidfk` FOREIGN KEY (`blog_id`) REFERENCES `Blog` (`id`) ON DELETE CASCADE
) ENGINE=InnoDB DEFAULT CHARSET=utf8;



Code between sessionFactory.openSession() and session.close():
Session session = _sessionFactory.openSession();
Transaction tx = null;

Blog blog = null;

try {
tx = session.beginTransaction();
Criteria blogCriteria = session.createCriteria(org.blojsom.blog.database.DatabaseBlog.class);
blogCriteria.add(Restrictions.eq("blogId", blogId));
blog = (Blog) blogCriteria.uniqueResult();

tx.commit();

if (blog == null) {
throw new FetcherException("Blog id: " + blogId + " not found");
}
} catch (HibernateException e) {
if (tx != null) {
tx.rollback();
}

if (_logger.isErrorEnabled()) {
_logger.error(e);
}

throw new FetcherException(e);
} finally {
session.close();
}



Name and version of the database you are using:mysql 5.0.27-community-nt

The generated SQL (show_sql=true):
五月 10 17:24:37 DEBUG [http-8080-Processor25] hibernate.SQL - select this_.id a
id10_0_, this_.blog_id as blog2_10_0_ from Blog this_ where this_.blog_id=?
五月 10 17:24:37 DEBUG [http-8080-Processor25] hibernate.SQL - select properties
_.blog_id as blog1_0_, properties0_.property_value as property2_0_, properties0
.property_name as property3_0_ from Properties properties0_ where properties0_.
log_id=?
五月 10 17:24:37 DEBUG [http-8080-Processor25] hibernate.SQL - select plugins0_.
log_id as blog1_0_, plugins0_.plugin_value as plugin2_0_, plugins0_.plugin_flav
r as plugin3_0_ from Plugin plugins0_ where plugins0_.blog_id=?
五月 10 17:24:37 DEBUG [http-8080-Processor25] hibernate.SQL - select templates0
.blog_id as blog1_0_, templates0_.template_value as template2_0_, templates0_.t
mplate_flavor as template3_0_ from Template templates0_ where templates0_.blog_
d=?
五月 10 17:24:37 DEBUG [http-8080-Processor25] hibernate.SQL - delete from Templ
te where blog_id=?
五月 10 17:24:37 DEBUG [http-8080-Processor25] hibernate.SQL - delete from Plugi
where blog_id=?
五月 10 17:24:37 DEBUG [http-8080-Processor25] hibernate.SQL - insert into Templ
te (blog_id, template_flavor, template_value) values (?, ?, ?)
...
五月 10 17:24:37 DEBUG [http-8080-Processor25] hibernate.SQL - insert into Plugi
n (blog_id, plugin_flavor, plugin_value) values (?, ?, ?)
...