iunique.py

class IUniqueIndex(models.Index):
    suffix = 'iuq'
    sql_template = 'CREATE UNIQUE INDEX %(name)s ON %(table)s (%(columns)s);'

    def create_sql(self, model, schema_editor, using=''):
        assert schema_editor.connection.vendor == 'postgresql'

        fields = [model._meta.get_field(field_name) for field_name, _ in self.fields_orders]
        quote_name = schema_editor.quote_name

        return self.sql_template % ({
            'name': quote_name(self.name),
            'table': quote_name(model._meta.db_table),
            'columns': ", ".join(['UPPER(%s)' % quote_name(field.column) for field in fields])
        })