I am having performance problems with my code, when trying to update a lot of records at once.

How to avoid retrieving the object if I want simply update it?
Simple code
Data data = myService.getData(dataId);
data.setSomething(something);
myService.save(data);

may produce unnecessary SELECT statements, when I need only one UPDATE statement.

I am running complex algorithms that basically generate clusters of data. Each piece of data then is supposed to updated with a cluster that it belongs to. Algorithm returns list of clusters, and each clusters has list of data ids, that belong to cluster. To update this data I use:

for(Long dataId : dataList) {

Data data = myService.getData(dataId);
data.setCluster(cluster);
myService.save(data);

}

Each iteration produce sth like this:

Hibernate: select need0_.id as id0_0_, need0_.created as created0_0_, ...............
Hibernate: select cluster0_.id as id3_0_, cluster0_.created ............
Hibernate: select user0_.id as id1_0_, user0_.created as created1_0_, .............
Hibernate: select project0_.id as id5_0_, project0_.created ..............
Hibernate: select joinedproj0_.user_id as user7_2_, joinedproj0_.id .........
Hibernate: update Need set updated=?, cluster_id=?, creator_id=?, project_id=?, score=?, text=? where id=?

I don't need all these SELECT's. I only want to do UPDATE per iteration. Imagine if I have 1000 iterations. Please help... I might still not understand some issues about hibernate, as I am new to it. If you need more details about the code let me know...

Thank you