Explain EXPLAIN ESTIMATE (children 1)
 SelectWithUnionQuery (children 1)
  ExpressionList (children 1)
   SelectQuery (children 2)
    ExpressionList (children 1)
     Function any (children 1)
      ExpressionList (children 1)
       Function toTypeName (children 1)
        ExpressionList (children 1)
         Identifier s
    TablesInSelectQuery (children 2)
     TablesInSelectQueryElement (children 1)
      TableExpression (children 1)
       Subquery (alias t1) (children 1)
        SelectWithUnionQuery (children 1)
         ExpressionList (children 1)
          SelectQuery (children 1)
           ExpressionList (children 5)
            Literal \'bbbbbbbb\'
            Function toTypeName (children 1)
             ExpressionList (children 1)
              Identifier s
            Function CAST (children 1)
             ExpressionList (children 2)
              Literal \'\'
              Literal \'LowCardinality(String)\'
            Literal NULL
            Function CAST (alias s) (children 1)
             ExpressionList (children 2)
              Literal \'\\0\\0\\0\\0\\0\\0\\0\\0\\0\\0\\0\\0\\0\\0\\0\\0\\0\\0\\0\\0\\0\\0\\0\\0\\0\\0\\0\\0\\0\\0\\0\\0\'
              Literal \'String\'
     TablesInSelectQueryElement (children 2)
      TableExpression (children 1)
       Subquery (alias t2) (children 1)
        SelectWithUnionQuery (children 1)
         ExpressionList (children 1)
          SelectQuery (children 2)
           ExpressionList (children 2)
            Function CAST (children 1)
             ExpressionList (children 2)
              Literal \'bbbbb\\0\\0bbb\\0bb\\0bb\'
              Literal \'LowCardinality(String)\'
            Function CAST (alias s) (children 1)
             ExpressionList (children 2)
              Function CAST (children 1)
               ExpressionList (children 2)
                Literal \'a\'
                Literal \'String\'
              Literal \'LowCardinality(String)\'
           ExpressionList (children 1)
            Function CoNnEcTiOn_Id (children 1)
             ExpressionList
      TableJoin (children 1)
       ExpressionList (children 1)
        Identifier s
