Hibernate version: 3.2.6

Could someone please clarify what the expected behavior of generated update statements are when you close a session? Currently if I do the following:

open a session
perform a query
close the session
open a session
call saveorupdate
close the session

then it generates a SQL updating most of my tables. However, if I don't close the session the first time:

open a session
perform a query
call saveorupdate
close the session

then it will just generate the sql for updating the one table I changed.

Is this the correct behavior? I can't find anything definitive in the documentation as to whether or not this is happening. I found in the documentation that this isn't how we should be doing it but it would be nice to get some clarification.

It seems, that this happens because your object-graph is detached after you close first session.
When you call saveOrUpdate in your second session, hibernate does not know, which objects have changed, it just does what you want it to do: saveOrUpdate.

You could call merge instead or enable select-before-update, but in either case your graph will be reloaded. Another solution would be disabling cascade-behaviour and update only the objects, which were modified by yourself.

Does closing the session automatically detach the session? I'm not calling session.detach() anywhere.

Object can only be persistent inside a session, when you close it the objects become detached.

Hibernate does not know if you manipulate 1 or 100 objects outside the session scope so it has to assume the worst.

Working as intended as far as i know

Why does hibernate need to form one query per object when using select-before-update?

Why can't it optimize that query into one select?