Hi,

I'm trying to fetch a list of objects where each root object has its own collections. Since there will be hundreds of thousands of instances I'd need to read them iterating over each one by one or with some kind of pagination. So far, I've been unable to do this.

The problem is that ScrollableResults seems to read rows, not objects. Let's say you have a "Parent" object with a collection of three "Child" objects. You will get after the joins three rows. Each call to ScrollableResults.next() retrieves the next row that means that you will have three parents with a child each.

Even using a .setResultTransformer(Criteria.DISTINCT_ROOT_ENTITY) in the criteria doesn't solve this.

Another way would be to set the first result and the number of results like:



But this also doesn't work. Again, it's row oriented, not object oriented.

How are you handling this ? Any comment about this would be really welcome.

Regards,

- Juan

I've been trying several combinations without success. As far as I can see Hibernate relies completly on the rows of the resultset returned by the JDBC driver.

Just to know if I should continue investing more time on this, does anyone know if, at least, is possible to retrieve objects with collections using a batch approach ?

The Query interface has an iterate() method. It populates a root entity when hasNext() is called. So, if your query sets FetchMode to join I think you'll get the batch in question and only one parent object.

I've had success loading lazy collections like this:



This provides me 1 root entity and * the associated collection I tell it to get (via setFetchMode). You can also create an alias and get collections of the setFetchMode collection instance - if that makes any scence at all :-).

e.g. objectA has many objectB's and objectB has many objectC's. You can use objectA to get objectsB's and use the alias & setFetchMode on objectB to get it's objectC's.

How are you using iterate() ? You can't set the fetch to "join" in the Query and then iterate.

In the docs (http://www.hibernate.org/hib_docs/v3/reference/en/html_single/#queryhql) is clearly stated that: Note that the fetch construct may not be used in queries called using iterate() (though scroll() can be used).

Sorry my friend...,

partA where I mention iterate() is not concrete - meaning I haven't implemented it. I was just trying to brainstorm with you. You'll notice the words "if" and "I think".

You did the right thing by looking further into the docs to see if it's doable.

PartB where I have an actual example is concrete and works.

Thank you for your comments anyway.

So far, I think this is a limitation in Hibernate. I'm giving up on this.