SelectWithUnionQuery (children 1)
 ExpressionList (children 1)
  SelectQuery (children 2)
   ExpressionList (children 1)
    Identifier _shard_num
   TablesInSelectQuery (children 1)
    TablesInSelectQueryElement (children 1)
     TableExpression (children 1)
      Function cluster (children 1)
       ExpressionList (children 2)
        Literal \'test_shard_localhost\'
        Identifier system.one
