Explain EXPLAIN AST (children 1)
 SelectWithUnionQuery (children 1)
  ExpressionList (children 1)
   SelectQuery (children 2)
    ExpressionList (children 2)
     Function tupleElement (children 1)
      ExpressionList (children 2)
       Asterisk
       Literal UInt64_2
     Function tupleElement (children 1)
      ExpressionList (children 2)
       Identifier x
       Literal UInt64_1
    TablesInSelectQuery (children 1)
     TablesInSelectQueryElement (children 1)
      TableExpression (children 1)
       Subquery (children 1)
        SelectWithUnionQuery (children 1)
         ExpressionList (children 1)
          SelectQuery (children 1)
           ExpressionList (children 1)
            Function arrayJoin (alias x) (children 1)
             ExpressionList (children 1)
              Function array (children 1)
               ExpressionList (children 1)
                Literal Tuple_(UInt64_0, UInt64_1)
