title: How to remove unique constraint for a model attribute of an abstract model after inheritance?
body: <p>I have an abstract class as:</p>
  
  <pre><code>class AbstractExecutive(models.Model):
      mobile = models.CharField(max_length=10,unique=True,
                                verbose_name='*Mobile')
  
     #other attributs not required....
      class Meta:
          abstract = True
  </code></pre>
  
  <p>I am inheriting this class to create different instances like Client,Vendor etc. For a class instance Client, I require that the unique constraint is dropped, while it exists for other class objects. I am using postgresql 9.1 I I dropped the the client table constraint using psql, but since the model is inherited, it always has unique constraint on it. Please note the Client table has data and cannot be disturbed. How can I get rid of the constraint in the table. Client class model:</p>
  
  <pre><code>class Client(AbstractAddress,AbstractExecutive):
  
      number = models.CharField(max_length=10,verbose_name='number',
                                    unique=True)
      #other attributes...
  </code></pre>