and so the engine calls current_thd to derive transaction information;
instead we now pass THD to those functions, it looks more logical
(it makes the implicit current_thd parameter more visible).
Approved by Brian and Monty.
Bugs fixed:
- Bug #20877: InnoDB data dictionary memory footprint is too big
- Bug #13544: Second delete of same row in transaction illustrates non-optimal locking
- Bug #20791: valgrind errors in InnoDB
In practice this means that handlerton is now created by the server and is passed to the engine. Plugin startups can now also control how plugins are inited (and can optionally pass values). Bit more flexibility to those who want to write plugin interfaces to the database.