[bknr-devel] objects with transient slots

[Kamen TOMOV]

Hans,

"transient" has some effect because none of the setf-s of slots of
this kind are in the transaction log, only when suppling data in the
:initarg they are written there. 

In the morning I built something that relies on that behaviour, but
then realized that it might not be what was intended. That's why I
mentioned taht this might be a feature ;) Anyway, I'll follow your
advise - thanks for it!

Perhaps wherever you use transient slots in your applications you setf
them instead of using :initargs on them and in result they are never
in the transaction log and things are fine.

Regards,

-- 
Камен


----- Original Message ----- 
From: Hans Hübner
Sent: 06 Юли 2007 at 14:50
Subject: Re: [bknr-devel] objects with transient slots

Kamen,

what you describes looks to me as if the :transient does not have any effect
at all, so the question is what you'd want to use this as a feature for :)
-  Seriously, what you describe seems to be a bug, as :transient slots
should never be logged.  In fact, I am depending on this behavior in several
places and I wonder how the store serializes the slots that I'm using.

I'd recommend to use :transient the way that is described in the
documentation, i.e. assume that such slots will not be restored.  I will
eventually fix this, but it will propably take a few days until I commit.

-Hans

2007/7/6, Kamen TOMOV <kamen at cybuild.com>:
>
> Hello Hans,
>
> Lets define a class:
>
> (define-persistent-class a ()
>   ((s1 :update :transient t)
>    (s2 :update)))
>
> and make an instance of it:
>
> (let ((obj (make-object 'a :s1 23 :s2 "ar")))
> ...
>
> and then modify its transient slot:
>
> (setf (a-s1 obj) 3)
>
> When I stop and start Lisp and do:
>
> (make-instance 'mp-store....
>
> I get:
>
> (slot-value obj 's1)
> => 23
> (slot-value obj 's2)
> => "ar"
>
> s1 is transient and one might expect it to be unbound, but it is not,
> so I wondered if it is a bug or a feature, cause I might decide to use
> it as a feature :-)
>
> However, I guess that if I snapshot and then restore the database the
> transient slot would be unbound (and that would prevent me from using
> it as a feature, but I probably need a persistent slot anyway). Am I
> correct?
>
>
> Regards,
>
> --
> Камен
>
>
> ----- Original Message -----
> From: Hans Hübner
> Sent: 06 Юли 2007 at 13:47
> Subject: Re: [bknr-devel] objects with transient slots
>
> Hi Kamen,
>
> are you saying that your transient slots are written to the transaction
> log
> and snapshot?  This is not the intended behavior.  Can you verify the bug
> by
> writing some distinctive string to such a slot, snapshot and then look in
> the snapshot file for that string?  Do you see the the value retained when
> restoring or when starting your lisp afresh?
>
> Thanks,
> Hans
>
> 2007/7/6, Kamen TOMOV <kamen at cybuild.com>:
> >
> > Hi,
> >
> > It is said in the datastore-manual:
> >
> > "... you can specify that a certain slot is transient, which means
> > that it will not be snapshotted and that its value can be changed
> > outside of a transaction."
> >
> > In my application the value of a transient slot is specified on object
> > creation. When reloading the transaction log (server restart) the
> > transient slot is bound and its value is correct. Is this intended
> > behaviour or not? How is snapshotting the database different in that
> > context?
> >
> > Thanks in advance,
> >
> > --
> > Kamen
> > _______________________________________________
> > bknr-devel mailing list
> > bknr-devel at common-lisp.net
> > http://common-lisp.net/cgi-bin/mailman/listinfo/bknr-devel
> >
>