SelectWithUnionQuery (children 1)
 ExpressionList (children 1)
  SelectQuery (children 1)
   ExpressionList (children 1)
    Function countSubstrings (children 1)
     ExpressionList (children 2)
      Function materialize (children 1)
       ExpressionList (children 1)
        Literal \'aaa\'
      Function materialize (children 1)
       ExpressionList (children 1)
        Literal \'\'