title: How to check MySQL performance?
body: <p>i have mysql that is used on production server for php webshop application.</p>
  
  <p>sometimes it works very slow. so, i will change indexes for several tables.</p>
  
  <p>but before that, i have to make some kind of "snapshot" of current performances (several times per day). after that, i will change indexes, and create new "performance snapshot". then i will made some more changes in database, and made another "performance snapshot".</p>
  
  <p>how can i make that "performance snapshot"? is it possible to use some kind of tool, or to ckeck some logs, or...?</p>
  
  <p>if you can help me how to do that.</p>
  
  <p>thank you in advance!</p>