title: Is it a good practice to add indexing on a boolean field in a Django model
body: <p>Suppose we have model with boolean field:</p>
  
  <pre><code>class AModel(models.Model):
      flag = models.BoleanField()
  </code></pre>
  
  <p>Is there any reason to add index on this field?</p>
  
  <p>I think it hasn't reason because there will be small profit in search(this only split two) but large overhead with recording. But my colleague thinks different.</p>
  
  <p>Is there any rule of thumb for this?</p>