In the WordPress database, one of the most heavily and intensively used tables is the posts table. It contains virtually all your content, and WordPress constantly queries it for your posts, pages, products, and other content types. Each type of content is represented by a post type (such as post, page, or product).

Having a large volume of data in this table is a common performance bottleneck for many WordPress sites. That’s why it’s important to determine whether some of your post types have become obsolete—perhaps used by plugins you’ve since uninstalled—or if they can be safely emptied from time to time.

You will see, for each post type, which plugin is using the table and how many posts are registered under that post type. If a post type exists but the associated plugin is not found on your installation, it will be highlighted in red.

The Clean action will delete all of the posts listed under that post type, so use it with caution.