SelectWithUnionQuery (children 1)
 ExpressionList (children 1)
  SelectQuery (children 2)
   ExpressionList (children 1)
    Function mapAdd (children 1)
     ExpressionList (children 2)
      Function tuple (children 1)
       ExpressionList (children 2)
        Literal Array_[\'a\', \'b\']
        Literal Array_[UInt64_1, UInt64_1]
      Function tuple (children 1)
       ExpressionList (children 2)
        Function array (children 1)
         ExpressionList (children 1)
          Identifier key
        Literal Array_[UInt64_1]
   TablesInSelectQuery (children 1)
    TablesInSelectQueryElement (children 1)
     TableExpression (children 1)
      Function values (children 1)
       ExpressionList (children 4)
        Literal \'key String\'
        Literal \'b\'
        Literal \'c\'
        Literal \'d\'
