title: Django models ForeignKey on_delete attribute: full meaning?
body: <p>Here some models:</p>
  
  <pre><code>class UserProfile(models.Model):  
      name = models.CharField(max_length=30)
      email = models.EmailField(unique=True, db_index=True) 
      birthday = models.DateField()
  
  class Photo(models.Model):
      user = models.ForeignKey(UserProfile)
      description = models.TextField(blank=True)
      photo = models.ImageField(upload_to='img/photo')
  </code></pre>
  
  <p>Let's say a user has 10 photos (10 objects of <code>Photo</code> model). When user deletes himself will all those 10 <code>Photo</code> database rows delete themselves automatically? (I've read docs, but English is not my native language, so I didn't understand everything about the <a href="https://docs.djangoproject.com/en/dev/ref/models/fields/#django.db.models.ForeignKey.on_delete"><code>on_delete</code></a> attribute.)</p>