Hello ,

Please let me know if I can have selective retrieval of attributes. For example, if I have a Catalog table which contains say 20 columns. There is one column of type CLOB which contains heavy data.While loading catalogs I do not want to fetch the CLOB for performance reasons. DOES HIBERNATE PROVIDES THIS FUNCTIONALITY ?????

I read Hibernate referencve guide and it mentions of FetchGroup.LAZY
I tried using this for the CLOB column but it doesnt work for me. Can I have lazy loading of simple attributes (which are not collections/entities)

The mapping file and the code snippet is provided : PlSSS let me know if I am missing something ?

<class name="com.aceva.rms.knowledge.config.Catalog" table="Catalog">
<id name="id" column="catalog_id" type="long" unsaved-value="null">
<generator class="sequence"/>
</id>
<property name="definition" column="definition" type="clob"/>
<property name="name" column="name" type="string" length="30"/>
</class>

try{
session = HibernateUtils.currentSession();
Criteria criteria = session.createCriteria(Catalog.class)
.setFetchMode("definition", FetchMode.LAZY);
List list = criteria.list();
for (int i = 0; i < list.size(); i++)
{
Catalog catalog = (Catalog) list.get(i);
logMessage("Catalog Fetched!");
Clob clob = catalog.getDefinition();
logMessage("asked for definition! " + clob.getClass().getName());
}
}

Help is urgently required!!!

Thanks in advance

Anjali

Maybe that you can use a lightweight and an heavyweight object with explicit polymorphism.

[url]http://www.hibernate.org/41.html [/url]

Mauro.

or projection

Clobs are lazy by definition! If your JDBC driver implements Clob support correctly, you should /not/ need to do anything special.

Thanks Everybody for the help ..

Yeah I went through the link which tells about the LightWeightPattern and I have implemented that and it worked for me. But this is not feasible
to implement in my current system at certain places
Q.1) I guess Hibernate must be providing some way to specify that these columns/atttributes should be lazily fteched . Either the user can specify it in configuration mapping file or like.. I guess JDO supports this Lazy fetching through mapping file.

Q.2) I read about FetchMode . Its provides diff fetch modes like LAZY, DEFAULT, EAGER. Are these not related to this ? Will they work only with associations ?? Not very clear on the usage of this.

Q.3) Can you quote me an example or any reference how projection can help me ? Are you talking about writing queries like select doc_id, doc_name, acc_no from document table (where document table has say 20 columns)
So in this case Hibernate is not providing me anything except the Pattern mentioned . Because for reporting and bulk load , this is a very important requirement and we need this greatly :-)

Hoping to get a reply soon

Thanks
Anjali

We don't really agree with that. loading a property is not really an overload except for huge amount of binary or txt in a field.
It was long discussed and we're quite happy with the previous workarounds.


Yes this is what projection is.