SelectWithUnionQuery (children 1)
 ExpressionList (children 1)
  SelectQuery (children 2)
   ExpressionList (children 1)
    Function toBool (alias should_be_equal) (children 1)
     ExpressionList (children 1)
      Function equals (children 1)
       ExpressionList (children 2)
        Identifier t1.val
        Identifier t2.val
   TablesInSelectQuery (children 2)
    TablesInSelectQueryElement (children 1)
     TableExpression (children 1)
      Subquery (alias t1) (children 1)
       SelectWithUnionQuery (children 1)
        ExpressionList (children 1)
         SelectQuery (children 3)
          ExpressionList (children 1)
           Identifier value (alias val)
          TablesInSelectQuery (children 1)
           TablesInSelectQueryElement (children 1)
            TableExpression (children 1)
             TableIdentifier system.server_settings
          Function equals (children 1)
           ExpressionList (children 2)
            Identifier name
            Literal \'mark_cache_policy\'
    TablesInSelectQueryElement (children 2)
     TableExpression (children 1)
      Subquery (alias t2) (children 1)
       SelectWithUnionQuery (children 1)
        ExpressionList (children 1)
         SelectQuery (children 1)
          ExpressionList (children 1)
           Function getServerSetting (alias val) (children 1)
            ExpressionList (children 1)
             Literal \'mark_cache_policy\'
     TableJoin
