title: Avoid SHOW FIELDS in ActiveRecord
body: <p>Is there any way to prevent ActiveRecord from issued a SHOW FIELDS to the database when it's not needed?</p>
  <p>I'm working on database performance critical application, and just noticed that on a typical query my SELECT takes 0.5 ms and the related SHOW FIELDS takes 2 ms -- 4 times longer! Even more importantly, it's not needed because I'm already specifying the only column I want to retrieve:</p>
  <p><code>UsersAddress.find(:all, :conditions =&gt; {:user_id =&gt; 1}, :select =&gt; :address_id)</code></p>
  <blockquote>
  <p>UsersAddress Load (0.5ms) SELECT address_id FROM <code>users_addresses</code> WHERE (<code>users_addresses</code>.<code>user_id</code> = 1)</p>
  <p>UsersAddress Columns (2.1ms) SHOW FIELDS FROM <code>users_addresses</code></p>
  </blockquote>
  <p>Granted, this only happens once each time some table is touched for the first time, but shouldn't it be avoidable complete? First of all, that info is already in my schema. Second, I don't need it.</p>
  <p>Any ideas how to optimize this so that Rails won't run a SHOW FIELDS unless it really needs it?</p>
  <p>Thanks!</p>