Tips to remove unwanted post revision and disable post revision features on WordPress:
1. SQL command to delete post revisions
DELETE FROM wp_posts WHERE post_type = “revision”;
2. Disable Post Revision features on WordPress
Add define(‘WP_POST_REVISIONS’, false); in your wp-config.php before the closing ?> tag
The original post is in http://www.techmixer.com/disable-and-remove-wordpress-revision-post-features/