This patch fixes an issue with Magento bizarre way of constructing queries to join all data required for category listings causing MySQL's table indexes to fail and queries to take 5 to 40 times longer than normal when using MySQL/MariaDB/Percona 5.7 and up.
I've only tested it on Magento 1.9.x. After installing this fix and flushing all your caches, your category pages (and other things that use category listings (think Megamenu or other stuff) will become really fast (again).
I'm pretty sure the problem still exists in Magento 2.x if they build their queries the same way as in one, for which I have no reason to believe that they don't.. feel free to correct me if I'm wrong.
Either copy the contents of the src folder to your Magento installation folder or deploy this module with modman.