Hibernate out of memory exception while processing large collection of elements

Question

I am trying to process collection of heavy weight elements (images). Size of collection varies between 8000 - 50000 entries. But for some reason after processing 1800-1900 e

Answer 1

You have confused flushing with clearing:

• flushing a session executes all pending statements against the database (it synchronizes the in-memory state with the database state);

• clearing a session purges the session (1st-level) cache, thus freeing memory.

So you need to both flush and clear a session in order to recover the occupied memory.

In addition to that, you must disable the 2nd-level cache. Otherwise all (or most of) the objects will remain reachable even after clearing the session.