Hi Douglas,
Ok, so I think I see the problem then - my apologies for not seeing it
sooner. The FDMS destination does not have a destination for the
"filmActors" type. Also, the property: "Actor.filmActors" has this
association tag:
<many-to-many
property="filmActors"
destination="film.hibernate"
lazy="true" />
it should instead refer to the new filmActors.hibernate destination you
would add. This type would have its identity property with the name
"id" and would have lazy one-to-one association properties both for
"film" and "actor" which refer to the destinations "film.hibernate" and
"actor.hibernate". One more thing is that because you are using a
"complex" object type as an identity property, your FilmActor.as class
will need a function like:
public function toString():String
{
return actorId + ":" + filmId
}
This is a requirement for complex object identity properties in FDMS
(due to the fact that there is no Hashtable like class in ActionScript
which uses equals/hashCode methods, we use a string key generated from
the toString values of all identity properties to keep track of
instances on the client).
I think the hibernate assembler is missing an error test for the case
where the type of the referenced entity does not match the destination's
entity type. I'll fix that right away as that would have saved you a
lot of time. Instead, it is looking for a "filmId" property on the
FilmActor type and is getting back null (it should also print an error
instead here).
One other thing I'll mention as an aside is that you could potentially
implement the Film/Actors relationship without an intermediate
FilmActors class - both hibernate and FDMS will support that and since
you do not have any additional properties in the mapping table, it is
pretty common to avoid an extra type.
You are right though that this fix will not greatly improve the
performance. We are still going to need to do a query for each actor to
retrieve the filmActors properties. It will be a little faster than
today because it won't need to join in the Film table because of the
intermediate mapping object.
Jeff
________________________________
From: [email protected] [mailto:[EMAIL PROTECTED] On
Behalf Of Douglas McCarroll
Sent: Thursday, November 30, 2006 5:39 PM
To: [email protected]
Subject: Re: [flexcoders] many-to-many managed association in Hibernate
destination
Hi Jeff,
A couple more thoughts...
It's worth noting that I don't get the error when I use the hierarchical
values approach without lazy loading, and get my films info from my
actor objects.
> Thanks for this info. The performance problem is most likely due to
the
> fact that FDMS is fetching the list of films for each actor... this is
> the lazy loading issue we have currently that I mentioned in a
previous
> post. If we were to follow the hibernate model more closely, we'd send
> "actor" instances to the client without having populated the list of
> films for each actor at all. The first "get" call made on the films
> property for a given actor would then go back to the server and fetch
> them. As it is now, we'll do one query to retrieve the list of actors,
> then a query for each actor to get its list of films. For a large DB,
> this is a lot of queries to do.
> This is a pretty high priority feature request. For now, the
workaround
> would be to modify your domain model so there is an intermediate
object
> but that is awkward when you are generating everything from the simple
> schema.
I'm not sure that I understand this. I believe that I have "an
intermediate object" - filmActor.java and filmActor.as.
Are you suggesting that I use that object - or rather those objects - as
a way of finding out what filmIds are related to an actorId? I.e. that I
load them from their own destination? I'm tired so if this isn't clear,
don't worry about it. :-)
Do I understand correctly that until we get the fix lazy loading isn't
necessarily going to solve any performance problems?
Douglas
Jeff Vroom wrote:
>
> Thanks for this info. The performance problem is most likely due to
the
> fact that FDMS is fetching the list of films for each actor... this is
> the lazy loading issue we have currently that I mentioned in a
previous
> post. If we were to follow the hibernate model more closely, we'd send
> "actor" instances to the client without having populated the list of
> films for each actor at all. The first "get" call made on the films
> property for a given actor would then go back to the server and fetch
> them. As it is now, we'll do one query to retrieve the list of actors,
> then a query for each actor to get its list of films. For a large DB,
> this is a lot of queries to do.
>
> This is a pretty high priority feature request. For now, the
workaround
> would be to modify your domain model so there is an intermediate
object
> but that is awkward when you are generating everything from the simple
> schema.
>
> As to why it is not working, from the output, the "filmId" of each
Film
> object is getting sent to the client as a "null" value. I am not sure
> why... I can't tell if it is retrieving the values from the database
as
> null or if FDMS is just not getting the values from the objects
> properly. It could have something to do with the "short" data type - I
> do not think we've tried id properties as short values so maybe
> something is getting messed up because of that? It might be worth
> changing that to an int if that is an easy test to run.
>
> I will try to get a chance to look at this more tomorrow.
>
> Jeff
>
> -----Original Message-----
> From: [email protected] <mailto:flexcoders%40yahoogroups.com>
<mailto:flexcoders%40yahoogroups.com>
> [mailto:[email protected]
<mailto:flexcoders%40yahoogroups.com>
> <mailto:flexcoders%40yahoogroups.com>] On
> Behalf Of Douglas McCarroll
> Sent: Wednesday, November 29, 2006 11:26 AM
> To: [email protected] <mailto:flexcoders%40yahoogroups.com>
<mailto:flexcoders%40yahoogroups.com>
> Subject: Re: [flexcoders] many-to-many managed association in
Hibernate
> destination
>
> Jeff Vroom wrote:
>
> > 4) If you turn on debug logging in the server for
> > the "Endpoint.*" logging category, you'll see the
> > object graph which is sent to the client after
> > your fill. I am curious if the time is being
> > spent loading the data from the database or
> > sending data to the client, or a combination of
> > both.
>
> Okay, I've figured out how to do this part. Results here:
>
>
http://www.brightworks.com/technology/tech_questions/hibernate_lazy_asso
<http://www.brightworks.com/technology/tech_questions/hibernate_lazy_ass
o>
>
<http://www.brightworks.com/technology/tech_questions/hibernate_lazy_ass
o
<http://www.brightworks.com/technology/tech_questions/hibernate_lazy_ass
o> >
> ciations/debug_log_01.txt
>
> > If you can also turn on debug logging of the SQL
> > that hibernate is using that would help figure out
> > if we are just fetching too many objects or what.
>
> It looks as though I do this by adding a line to
> HibernateManager.java...
>
> public void createSessionFactory(Configuration hibernateConfig,
> boolean useTransactions) throws ExceptionInInitializerError
> {
> try
> {
>
> New Line -> hibernateConfig.setProperty("hibernate.show_sql", "true")
>
> sessionFactory = hibernateConfig.buildSessionFactory();
>
> Yes?
>
> BTW, in case someone finds this someday with Google, here are some
> resources:
>
> FDS Logging:
>
>
http://livedocs.macromedia.com/flex/2/docs/wwhelp/wwhimpl/common/html/ww
<http://livedocs.macromedia.com/flex/2/docs/wwhelp/wwhimpl/common/html/w
w>
>
<http://livedocs.macromedia.com/flex/2/docs/wwhelp/wwhimpl/common/html/w
w
<http://livedocs.macromedia.com/flex/2/docs/wwhelp/wwhimpl/common/html/w
w> >
> help.htm?context=LiveDocs_Parts&file=00001112.html
>
>
http://weblogs.macromedia.com/dharfleet/archives/2006/08/debugging_flex.
<http://weblogs.macromedia.com/dharfleet/archives/2006/08/debugging_flex
.>
>
<http://weblogs.macromedia.com/dharfleet/archives/2006/08/debugging_flex
.
<http://weblogs.macromedia.com/dharfleet/archives/2006/08/debugging_flex
.> >
> cfm
>
> http://tech.groups.yahoo.com/group/flexcoders/message/56192
<http://tech.groups.yahoo.com/group/flexcoders/message/56192>
> <http://tech.groups.yahoo.com/group/flexcoders/message/56192
<http://tech.groups.yahoo.com/group/flexcoders/message/56192> >
>
> Hibernate Logging:
>
> http://www.javalobby.org/java/forums/t44119.html
<http://www.javalobby.org/java/forums/t44119.html>
> <http://www.javalobby.org/java/forums/t44119.html
<http://www.javalobby.org/java/forums/t44119.html> >
>
> --
> Flexcoders Mailing List
> FAQ: http://groups.yahoo.com/group/flexcoders/files/flexcodersFAQ.txt
<http://groups.yahoo.com/group/flexcoders/files/flexcodersFAQ.txt>
> <http://groups.yahoo.com/group/flexcoders/files/flexcodersFAQ.txt
<http://groups.yahoo.com/group/flexcoders/files/flexcodersFAQ.txt> >
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<http://www.mail-archive.com/flexcoders%40yahoogroups.com> >
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>
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