Thorsten Möller, yes, I think we should use executeUpdate() for update().

If you try to run Query#executeUpdate() with OGM you'll get an UnsupportedOperationException, so that'd be the starting point. Essentially, from there you'd have to run the query through the grid dialect. We'll need a new method on QueryableGridDialect which doesn't return an iterator but just the number of affected rows.

As far as findAndModify() is concerned, yes, a normal query is probably as good as it gets.

Also check out this document with some more general info on getting started with contributing to Hibernate OGM. If you run into any issues, just let me know; We hang out on #hibernate-dev on FreeNode or you send a mail to the "hibernate-dev" mailing list.