What does "Clear All Sessions" actually do?

Hey,

I’ve just been looking into a problem for a friend with his site getting pretty slow – and found that there were quite a lot of WooCommerce sessions in the wp_options table (nearly two million, in fact). Now, I’ve taken some steps to stop bots spamming them (added /add-to-cart to the robots.txt), but now I have the trouble of actually getting rid of the sessions that are slowing the site down.

I assume that ‘Clear All Sessions’, next to ‘Customer Sessions’ will do this – but will it have any other side effects I was not expecting? Such as, will it interfere with orders or client profiles (beyond wiping their current baskets). Also, what will happen if somebody is in the middle of making a purchase and I clear the sessions.

Cheers in advance.

https://wordpress.org/plugins/woocommerce/