title: Django save with update_fields and POSTGRESQL MVCC
body: <p>I search on internet but I don't find informations about that, if I look at Heroku Devcenter I have this information:</p>
  
  <p>url: <a href="https://devcenter.heroku.com/articles/postgresql-concurrency#disadvantages-of-mvcc" rel="nofollow noreferrer">https://devcenter.heroku.com/articles/postgresql-concurrency#disadvantages-of-mvcc</a></p>
  
  <p>"This is why an UPDATE actually creates a new row", </p>
  
  <p>So if Postgresql actually creates a new row for each update, does it make any sense to use update_fields to increase performance?</p>
  
  <p>I will in a few days create a little benchmark to test if there is any performance improvement in using update_fields.</p>