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Date: Fri, 2 Sep 2011 16:28:09 +0100
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Subject: Re: Data base externally modified
From: Anthony Brew <anthony.brew@swrve.com>
To: user@cayenne.apache.org
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Hi,
    Just an update, and I think I forgot to include something important
Its a one to many relationship that I am seeing cached, (ie I fetch "Item"
and the many to one "Item.getSubItems()" are being fetched from the cache)

My code now looks a bit like:

        Expression e1 = Expression.fromString("id = $id");
        Map params = new HashMap();
        params.put("id", item.getId());

        SelectQuery query = new SelectQuery(Item.class,
e1.expWithParameters(params));
        query.setCacheStrategy(QueryCacheStrategy.NO_CACHE);

        List items = context.performQuery(query);
        if(items.size() != 1){
            throw new RuntimeException("");
        }
        freshitem = (Item) items.get(0);

        subitems = freshitem.getSubItems()

Where subitems are stale.

I am sure I am making this more complicated than needs be. As I mentioned
before I would like to turn on some flag to essentially always read from DB
when I do items.getSubItems() if possible, or when I reload the Item when
its getter methods are called to make it always read from the DB the first
time when QueryCacheStrategy.NO_CACHE is specified...

Thanks a Million,
Anthony


On Fri, Sep 2, 2011 at 3:54 PM, Mike Kienenberger <mkienenb@gmail.com>wrote:

> You may want to review these two threads from the end of July:
>
> OSCache is gone
> http://www.mail-archive.com/dev@cayenne.apache.org/msg06209.html
>
> EhCache integration preview
> http://www.mail-archive.com/user@cayenne.apache.org/msg06211.html
>
>
> On Fri, Sep 2, 2011 at 10:30 AM, Anthony Brew <anthony.brew@swrve.com
> >wrote:
>
> > Hi Andrus,
> >               I was just about to get back to you on, I accidentally
> > started two threads when I joined the mailing list.
> >
> > Essentially we have a ruby on rails project that creates config on the
> > front
> > end, this is the part that is changing externally. Then internally we
> read
> > these config and do a bunch of processing and write the results to a
> > separate set of tables. The tables are in turn read by the R on R app but
> > never written to
> >
> > so
> > Tables      Set A                   |     Set B
> > ------------------------------------------------------------------------
> > Rails       read and write         |     read only
> > Java        read only               |     read and write
> >
> > The issues I am facing are with set A changing in the app.
> >
> > I have tried forcing the Item to reload by doing this, (I cut code from
> > Cayennes:     DataObjectUtils.objectForPK(threadDataContext, Item.class,
> > dirtyItem.getId());)
> >
> > private Item getItemWithNoCayenneCache(Item newGame, DataContext
> > threadDataContext) {
> >        ObjectId gameIdentifier = buildId(threadDataContext, Game.class,
> > newGame.getId());
> >
> >        return (Item) DataObjectUtils.objectForQuery(threadDataContext,
> new
> > ObjectIdQuery(
> >                gameIdentifier,
> >                false,
> >                ObjectIdQuery.CACHE_REFRESH));
> >    }
> > }
> >
> >
> > stepping into *DataObjectUtils.objectForQuery stepping into the Cayenne
> > code
> > I eventually get to DataContext.java*
> > *
> > *
> > where I see the following method called
> >
> > *
> > @Override
> > @SuppressWarnings("unchecked")
> > public List performQuery(Query query) {
> >        query = nonNullDelegate().willPerformQuery(this, query);
> >        if (query == null) {
> >            return new ArrayList<Object>(1);
> >        }
> >
> >        List result = onQuery(this, query).firstList();
> >        return result != null ? result : new ArrayList<Object>(1);
> > }
> > *
> >
> > however i see that the delgate in *
> > nonNullDelegate() is null and so I get back NoopDelegate.noopDelegate
> which
> > I assume is the route of my woes.
> > *
> > *
> >
> > *
> > Im interested in trying the OSCache solution you proposed in my other
> > thread, but I am a little wary the code is stale as my maven dependancies
> > fail (I am actually pretty new to maven so this might be my bad).
> > OSCache appears to be quite old since the OpenSymphony project died,
> maybe
> > my maven config is off, are there still active contributors?
> >
> > In my pom I have specified
> > <dependency>
> > <groupId>opensymphony</groupId>
> >    <artifactId>oscache</artifactId>
> >     <version>2.4</version>
> >  </dependency>
> >
> > however the dependancies on
> >
> >   - javax.jms:jms:1.1
> >
> > Thanks a Million
> > Anthony
> >
> >
> > On Fri, Sep 2, 2011 at 2:34 PM, Andrus Adamchik <andrus@objectstyle.org
> > >wrote:
> >
> > > Could you please explain your data access patterns?
> > >
> > > E.g. if you fetch some objects and store them in an instance variable
> in
> > > your application, they are not going to get refreshed automatically. To
> > > refresh objects you need to either invalidate them explicitly via
> > > context.invalidateObjects() or run a query. All the cache settings are
> > > essentially about optimizing query execution (refresh data, but only as
> > > often as needed).
> > >
> > > Andrus
> > >
> > > On Sep 2, 2011, at 9:28 AM, Anthony Brew wrote:
> > >
> > > > Hi Gary,
> > > >            Yeah thats what I am seeing in the code, but I cant for
> the
> > > life
> > > > of me see how to turn off the caching completely in the modeller, I
> > > actually
> > > > think it wont hit our performance very badly to have no caching.
> > > >
> > > > The cache setting I see are the in the DataDomain Configuration
> > > >
> > > > Which has an option for a Query Cache Factory with a choice of two
> > > classes.
> > > >      - org.apache.cayenne.cache.MapQueryCacheFactory
> > > >      - org.apache.cayenne.cache.OSQueryCacheFactory
> > > >
> > > > I selected the MapQueryCache and trie to set the size of the object
> > cache
> > > to
> > > > 1 (couldn't set this to zero) as the application barfed saying caches
> > had
> > > to
> > > > be greater than size zero.
> > > >
> > > > in my cayenne.xml I see the line
> > > >
> > > > <property name="cayenne.DataRowStore.snapshot.size" value="1"/>
> > > >
> > > > was added, perhaps there is some manual setting I can add to this
> file
> > to
> > > > turn caching off?
> > > >
> > > > All the Best,
> > > > Anthony
> > > >
> > > >
> > > >
> > > > On Fri, Sep 2, 2011 at 12:20 AM, Gary Jarrel <garyjarrel@gmail.com>
> > > wrote:
> > > >
> > > >> I'd say that would be cache related, as Cayenne is caching the data
> > > >> from the database, switch the cache of in the Modeler perhaps and
> that
> > > >> should fix your problem.
> > > >>
> > > >> G
> > > >>
> > > >> On Fri, Sep 2, 2011 at 3:04 AM, Anthony Brew <
> anthony.brew@swrve.com>
> > > >> wrote:
> > > >>> Hi,
> > > >>>   I have a two processes one which writes to a several database
> > tables
> > > >> (a
> > > >>> ruby on rails application) and a java application that reads the
> > state
> > > >> these
> > > >>> data base tables using Cayenne and writes to other tables.
> > > >>>
> > > >>> When the ruby modifies the underlying data-base I am seeing that
> > > Cayenne
> > > >> is
> > > >>> not automatically picking up that the underlying data is now
> > > inconsistant
> > > >>> and not reloading. Is there some way I can config Cayenne to
> > aggressive
> > > >>> check some tables for updates while ignoring others?
> > > >>>
> > > >>> Thanks a Million
> > > >>> Anthony Brew
> > > >>>
> > > >>
> > >
> > >
> >
>

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