SelectWithUnionQuery (children 1)
 ExpressionList (children 1)
  SelectQuery (children 1)
   ExpressionList (children 2)
    Function match (children 1)
     ExpressionList (children 2)
      Function materialize (children 1)
       ExpressionList (children 1)
        Literal \'a key="v" \'
      Literal \'key="(.*?)"\'
    Function REGEXP_MATCHES (children 1)
     ExpressionList (children 2)
      Function materialize (children 1)
       ExpressionList (children 1)
        Literal \'a key="v" \'
      Literal \'key="(.*?)"\'