title: Query with where is not use index
body: <p>I have two tables, users and products. In users there are 4 users and products has a fk to users (column user_id).</p>
  <p>In products there are 2395288 records of which 765277 are with user_id = 4.</p>
  <p>Without index if I do</p>
  <blockquote>
  <p>explain select * from products where user_id = 4;</p>
  </blockquote>
  <p>I get</p>
  <p><a href="https://i.stack.imgur.com/HY80B.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/HY80B.png" alt="enter image description here" /></a></p>
  <p>So, I added an index</p>
  <blockquote>
  <p>CREATE INDEX userid ON products(user_id)</p>
  </blockquote>
  <p>After that, I executed again but the index doesn`t work:</p>
  <blockquote>
  <p>explain select * from products where user_id = 4;</p>
  </blockquote>
  <p><a href="https://i.stack.imgur.com/weKO5.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/weKO5.png" alt="enter image description here" /></a></p>
  <p>Only works if I do  select count(*) or select user_id</p>
  <p><a href="https://i.stack.imgur.com/x45xl.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/x45xl.png" alt="enter image description here" /></a></p>
  <p>But I need the index to select *  or select name, description to products where user_id = x</p>