Version Cleaning

following scenario:

I sometimes have to get a database dump from a client environment (author).

What is the fastest possible way to get rid of all versions in all workspaces?

And, way more important, to clear / run gc on the datastore somehow afterwards, as obviously the most data is assets and i want to not simple get rid of version info but of course as well of the related binaries of the versions.
I tried the version cleaner module, but that somehow runs into stackoverflow errors.
Also tried deleting the content of the version tables and the indexes of that and afterwards using the repository tools app to clear the repository (as i understand this triggers the datastore GC) but still my datastore table shows no change in size.

Regards,

Christoph