I was scrolling down a page of about 225 tables in PHPMyAdmin this morning, and I finally asked myself what the fuck the ‘Overhead’ column was supposed to mean. You know, that last, cryptic column in the listing of tables that has ‘–’ or ‘## bytes’ in it?

So I did some Googling and figured out what the fuck it is.

The overhead you’re seeing in phpMyAdmin isn’t anything to do with the MySQL settings. When records are deleted in MySQL, the space is never reclaimed until you optimize the table. Thus phpMyAdmin shows you how much space is “wasted” due to stuff that has been deleted. The user’s database frequently gets stuff deleted from it, (if you are using the email verification, alot [sic] of signups never get verified and automatically deleted. The online table and search results table hold tempoary info and so they bloat quite regularly. The busier the site, the more this will happen. That’s why optimizing those tables with high overhead frequently is important.

Thanks to JoshPet over at Ubb.Dev.