Wt

Short version:

Some dbo::ptr data seem to be not consistently updated if changed from another user; using the reread fixes the problem; how much does it cost to reread a dbo::ptr every time that I load (like in Wt::Dbo::Session::load) it, either by an explicit reread or activating the reread flag in Wt::Dbo::Session::load?

The online ref docs say that the value is not necessarily loaded again from the DB, which seems to point to a not excessive waste of DB readings, yet I wonder then why, if the system doesn't load it from the DB, the reread fixes this problem (and, if it reads again the ptr effectively only if 'needed', it doesn't realize that a ptr with some associated obsolete data should anyway be reread).

Long version:

I have built a chat with a ban system, moderator levels and such; when a "moderator" executes a ban or a mute, both his level and the other user's level are checked (so that a moderator cannot ban an admin, for example). To do so I blindly call a wrapper of the load function (DB::Ptr is a wrapper for dbo::ptr and so on...) for both the parts

template <class DBElement, class WidgetClass>

DB::Ptr UserDBSession::safeLoad_withinTransaction(const DB::IdType &id_int, WidgetClass *widget)

{

DB::Ptr p;

try

{

p=this->getSession().load(id_int);

}

catch (DB::ObjectNotFoundException)

{

return DB::Ptr();

}

CATCH_UNEXPECTED_EXCEPTION(this, widget);

return p;

}

Which then I call like this:

DB::Ptr p_ban_creator=session_.safeLoad_withinTransaction(creatorID);

This system includes, obviously, a way for the admin to increase or decrease the level of the other users.

The problem is that when the admin A changes the level of another user X, while this is correctly registered in the DB (I checked opening the DB with an extern program: DB Browser for SQLITE), when the user X tries to ban/mute another user (B), an action which activates the comparison between the levels of X and B, loading the two ptr as shown above, the result is that X's level is still the old level and not the new one (which is in the DB).

Using a reread fixes this, but at this point either there is a specific reason for the error to be there, or as a safe measure I'm supposed to reread the ptr every single time (ie: setting always the reread flag of the ::load function to true).

But I'd like to know if this implies an excessive waste of resources if the reread is, indeed, not needed.

Thanks.