AlterQuery  mt_with_pk (children 2)
 ExpressionList (children 1)
  AlterCommand ADD_INDEX (children 1)
   Index (children 2)
    Function plus (children 1)
     ExpressionList (children 2)
      Identifier z
      Identifier w
    Function minmax (children 1)
     ExpressionList
 Identifier mt_with_pk