How Get Rid of Revisions?

I think I’ve found how to prevent prior versions from being saved (per Codex, turning off the constant ‘wp_post_revisions’ in \htdocs\wordpress\wp-inclues\default-constants.php), but how do we get rid of the blizzard of revisions already there? There doesn’t seem to be any mechanism — even to eliminate them manually, one-by-one.