Many of WordPress users are unaware of Post Revisions, whenever you edit any particular post in your blog then a new row get created in wp_posts table, it shows the number of times a particular post have been edited. If you are only a author on your blog, then there is no need of this service as because it fillup the wp_posts table.

Well, if you wish you can delete the Pre-existing Post Revisions from a wordpress Plugin named as WP-Optimize. It let you to delete all post revisions from the wordpress dashboard panel.

Get WP-Optimize Plugin from here

After Activating it, Just go to → WordPress Dashboard panel → Scroll the Dashboard menu → Wp-Optimize → Select “Remove all Post revisions” → Process.

Remember: Take backup before deleting or optimizing database with WP-Optimize.

Also take a look @ WordPress section for more tricks & themes