title: Indexing boolean fields
body: <p>Is there going to be much benefit in indexing a boolean field in a database table?</p>
  <p>Given a common situation, like &quot;soft-delete&quot; records which are flagged as inactive, and hence most queries include <code>WHERE deleted = 0</code>, would it help to have that field indexed on its own, or should it be combined with the other commonly-searched fields in a different index?</p>