protected  void flushEverythingToExecutions(FlushEvent event) throws HibernateException 
{
		log.trace("flushing session");
		EventSource session = event.getSession();
		final PersistenceContext persistenceContext = session.getPersistenceContext();
		session.getInterceptor().preFlush( new LazyIterator( persistenceContext.getEntitiesByKey() ) );
		prepareEntityFlushes(session);
		// we could move this inside if we wanted to
		// tolerate collection initializations during
		// collection dirty checking:
		prepareCollectionFlushes(session);
		// now, any collections that are initialized
		// inside this block do not get updated - they
		// are ignored until the next flush
		persistenceContext.setFlushing(true);
		try {
			flushEntities(event);
			flushCollections(session);
		}
		finally {
			persistenceContext.setFlushing(false);
		}
		//some statistics
		if ( log.isDebugEnabled() ) {
			log.debug( "Flushed: " +
					session.getActionQueue().numberOfInsertions() + " insertions, " +
					session.getActionQueue().numberOfUpdates() + " updates, " +
					session.getActionQueue().numberOfDeletions() + " deletions to " +
					persistenceContext.getEntityEntries().size() + " objects"
				);
			log.debug( "Flushed: " +
					session.getActionQueue().numberOfCollectionCreations() + " (re)creations, " +
					session.getActionQueue().numberOfCollectionUpdates() + " updates, " +
					session.getActionQueue().numberOfCollectionRemovals() + " removals to " +
					persistenceContext.getCollectionEntries().size() + " collections"
				);
			new Printer( session.getFactory() ).toString( 
					persistenceContext.getEntitiesByKey().values().iterator(), 
					session.getEntityMode() 
				);
		}
}

Coordinates the processing necessary to get things ready for executions as db calls by preping the session caches and moving the appropriate entities and collections to their respective execution queues.

 protected Object getAnything() 
{
 return null;
}

 protected CascadingAction getCascadingAction() 
{
		return CascadingAction.SAVE_UPDATE;
}

 protected  void performExecutions(EventSource session) throws HibernateException 
{
		log.trace("executing flush");
		try {
			session.getJDBCContext().getConnectionManager().flushBeginning();
			// we need to lock the collection caches before
			// executing entity inserts/updates in order to
			// account for bidi associations
			session.getActionQueue().prepareActions();
			session.getActionQueue().executeActions();
		}
		catch (HibernateException he) {
			log.error("Could not synchronize database state with session", he);
			throw he;
		}
		finally {
			session.getJDBCContext().getConnectionManager().flushEnding();
		}
}

Execute all SQL and second-level cache updates, in a special order so that foreign-key constraints cannot be violated:
1. Inserts, in the order they were performed
2. Updates
3. Deletion of collection elements
4. Insertion of collection elements
5. Deletes, in the order they were performed

 protected  void postFlush(SessionImplementor session) throws HibernateException 
{
		log.trace( "post flush" );
		final PersistenceContext persistenceContext = session.getPersistenceContext();
		persistenceContext.getCollectionsByKey().clear();
		persistenceContext.getBatchFetchQueue()
				.clearSubselects(); //the database has changed now, so the subselect results need to be invalidated
		Iterator iter = persistenceContext.getCollectionEntries().entrySet().iterator();
		while ( iter.hasNext() ) {
			Map.Entry me = (Map.Entry) iter.next();
			CollectionEntry collectionEntry = (CollectionEntry) me.getValue();
			PersistentCollection persistentCollection = (PersistentCollection) me.getKey();
			collectionEntry.postFlush(persistentCollection);
			if ( collectionEntry.getLoadedPersister() == null ) {
				//if the collection is dereferenced, remove from the session cache
				//iter.remove(); //does not work, since the entrySet is not backed by the set
				persistenceContext.getCollectionEntries()
						.remove(persistentCollection);
			}
			else {
				//otherwise recreate the mapping between the collection and its key
				CollectionKey collectionKey = new CollectionKey( 
						collectionEntry.getLoadedPersister(), 
						collectionEntry.getLoadedKey(), 
						session.getEntityMode() 
					);
				persistenceContext.getCollectionsByKey()
						.put(collectionKey, persistentCollection);
			}
		}
		session.getInterceptor().postFlush( new LazyIterator( persistenceContext.getEntitiesByKey() ) );
}

1. Recreate the collection key -> collection map 2. rebuild the collection entries 3. call Interceptor.postFlush()