I'm tearing my hair out at the following problem.
I have a database of products. each product links to an imageSet object which I DO NOT want to be loaded unless I explicitly call getImages(). Hibernate3 claims to use lazy (proxy) fetching by default for associations, and I have even set lazy="true" for both the child class and the association but to no avail. Calling list() on a query for all products initializes the images too (causing a massive database hit).

Am I doing something stupid? Have I missed a setting?
I have grepped for any fetch or lazy settings just to check I hadn't changed any defaults, and I haven't.

Hibernate version:
3.0.5

Mapping documents:
<class name="org.trapdoor.bedsdirect.client.entities.Product">
<id name="id">
<column name="id"/>
<generator class="identity"/>
</id>
<version type="long" unsaved-value="undefined" name="version"/>
...
<many-to-one unique="true" lazy="true" name="images">
<column name="imageset"/>
</many-to-one>
<many-to-one unique="true" lazy="true" name="hoverImages">
<column name="hoverimageset"/>
</many-to-one>
...
</class>

<class lazy="true" name="org.trapdoor.bedsdirect.client.entities.ImageSet">
<id name="id">
<column name="id"/>
<generator class="identity"/>
</id>
<version type="long" unsaved-value="undefined" name="version"/>
<component name="small">
<property name="mimeType" column="small_mimeType"/>
<property name="base64Data" type="text" column="small_base64Data"/>
</component>
<component name="medium">
<property name="mimeType" column="medium_mimeType"/>
<property name="base64Data" type="text" column="medium_base64Data"/>
</component>
<component name="large">
<property name="mimeType" column="large_mimeType"/>
<property name="base64Data" type="text" column="large_base64Data"/>
</component>
</class>

Code between sessionFactory.openSession() and session.close():
s.createQuery("select p from Product p").list();

Name and version of the database you are using:
MySql 4.1.12

The generated SQL (show_sql=true):
14:58:39,423 DEBUG SQL:324 - select product0_.id as id, product0_.version as version19_, product0_.name as name19_, product0_.shortDescription as shortDes4_19_, product0_.full14:58:41,766 DEBUG SQL:324 - select imageset0_.id as id0_, imageset0_.version as version11_0_, imageset0_.small_mimeType as small3_11_0_, imageset0_.small_base64Data as small41

Debug level Hibernate log excerpt:
...(145 products loaded)...
14:58:41,762 DEBUG Loader:528 - total objects hydrated: 145
14:58:41,763 DEBUG TwoPhaseLoad:96 - resolving associations for [org.trapdoor.bedsdirect.client.entities.Product#1]
14:58:41,764 DEBUG DefaultLoadEventListener:143 - loading entity: [org.trapdoor.bedsdirect.client.entities.ImageSet#1]
14:58:41,764 DEBUG DefaultLoadEventListener:290 - attempting to resolve: [org.trapdoor.bedsdirect.client.entities.ImageSet#1]
14:58:41,765 DEBUG DefaultLoadEventListener:326 - object not resolved in any cache: [org.trapdoor.bedsdirect.client.entities.ImageSet#1]
14:58:41,765 DEBUG BasicEntityPersister:2467 - Materializing entity: [org.trapdoor.bedsdirect.client.entities.ImageSet#1]
14:58:41,765 DEBUG Loader:1340 - loading entity: [org.trapdoor.bedsdirect.client.entities.ImageSet#1]
14:58:41,766 DEBUG AbstractBatcher:290 - about to open PreparedStatement (open PreparedStatements: 0, globally: 0)
14:58:41,767 DEBUG AbstractBatcher:378 - preparing statement
14:58:41,848 DEBUG LongType:59 - binding '1' to parameter: 1
14:58:42,378 DEBUG AbstractBatcher:306 - about to open ResultSet (open ResultSets: 0, globally: 0)
14:58:42,379 DEBUG Loader:405 - processing result set
14:58:42,379 DEBUG Loader:410 - result set row: 0
14:58:42,380 DEBUG Loader:828 - result row: EntityKey[org.trapdoor.bedsdirect.client.entities.ImageSet#1]

Well I THINK I've found the problem.
setting lazy=true JUST on the ImageSet (child) class works.
I has the association set to lazy=true as well, and this seems to break it.

Surely this is a hibernate bug?

read the doc, many-to-one lazy=true means something different than proxy

From the hibernate reference:



If I understand correctly, lazy="true" should still specify lazy fetching, just using bytecode instrumentation rather than proxies. It still shouldn't hit the database.

Also, having "true","false",and "proxy" options is more than a little confusing!

I am now having a similar problem where a collection is being fetched along with the parent.

I have a bidirectional (many-to-many) association, with each end (supposedly) defaulting to lazy (I have also tried setting lazy=true).

doing a "from child" causes a select on the association table for each child returned! Surely this should happen on a per-child basis, when the collection is accessed?

Thanks for your help[/quote]

You probably did not enhance your classes, so <many-to-one lazy="true" just cannot work.

Hmm, not sure what you mean by not enhancing my classes. This is done at runtime by hibernate IIRC. Anyway, the many-to-one lazy="true" does now work, it's the many-to-many I'm having problems with.

Both ends of the bidirectional association are defined as "<set...<many-to-many...", and querying for the parents does NOT initiate a series of selects on the association table. Querying for the children DOES however. I've tried without overriding fetch and lazy settings, and also by overriding fetch="select" lazy="true" and just fetch="select". Nothing seems to make a difference - retrieving the children always hits the database.

Thanks again for your time/help

Ok, having read the docs more thoroughly:

<set> has lazy and fetch attributes, which default to "true" and "select" respectively, which is what I want.
<many-to-many> has only a fetch attribute which defaults to "join". I don't understand how this works, since now the set and many-to-many defaults conflict.

I set fetch="select" on the many-to-many tag but it makes no difference (and the SQL was showing multiple selects, not joins anyway.

Why isn't the collection being lazily fetched?

Oops, slightly embarassing. I had a debugging method hidden away that accessed the size of the collection. Sorry!