class metal_revision(osv.osv): _name = 'metal.revision' _rec_name = 'revision_no'

def _return_revision(self, cursor, user, field, context=None):            
#values=False  
#if not context.get('metal_revision_relation'):
   #return False        

qur=("""select revision_no from metal_revision where metal_revision_relation=3""" )
cursor.execute(qur)
    r = cursor.fetchall()
values=r[0]
return values   

_columns = {

    'revision_no': fields.char('Revsion No.', size=50,required=True,),
    'description':fields.char('Description', size=250),
    'residual_total':fields.float('Residucal Total',digits=(16,2)),
    'active':fields.boolean('Active'),
     'elements_line_ids':fields.many2many           ('metal.element','metal_elements_relation','metal_element_id','elements_line_ids','Elements'),
    'metal_revision_relation' : fields.many2one('metal.metal', 'Revision metal id'),        

}

i want only the selected field values(revision_no) should be return in '_rec_name' for dat i wrote sql query but how to call function in _rec_name