Hi James,
as far as I remember, CALL SQL does only work for select statements but
not for update or insert. You have to use JDBC for this kind of things.
Having said that you have to take care on cached objects that you have
updated through JDBC. Castor does not know about the database changes
and will hold dirthy objects in its cache. This will lead to
ObjectModifiedExceptions thrown when updating these objects through
Castor. Another problem is that you do not instantly see your changes
done by JDB statements. Therefore you need to set cache type to none or
remove the updated object from cache. While I have used the first myself
I have no experience about the second solution.
Regards
Ralf
James Abley schrieb:
> Actually, it doesn't look like I can drop into raw SQL in this way.
>
> CALL SQL UPDATE myObject SET field = $1 WHERE ID = $2
>
> That doesn't get parsed properly by OQLQueryImpl.createCall - it looks
> for the WHERE clause and examines the statement for $x tokens after the
> string value WHERE, rather than checking the whole statement. Later,
> OQLQueryImpl.bind(Object) throws a NullPointerException when it tries to
> bind the first parameter, and can't find a ParamInfo object in the
> _paramInfo field keyed on Integer(1).
>
> So it looks like I will have to drop into JDBC to use this sort of
> update approach.
>
> Should I raise a JIRA ticket about the OQL parsing?
>
> Cheers,
>
> James
>
> James Abley wrote:
>> To provide more context, I'm seeing locking and
>> LockNotGrantedException problems with a part of the application that
>> tries to update a single field in a root object, and
>> LockNotGrantedExceptions happen over the root object, or something in
>> the related object graph. I'm leaning towards the idea of swapping out
>> the current implementation for a simple raw SQL 'UPDATE MyObject SET
>> field = ? WHERE ID = ' approach to see if that removes the problem and
>> was wondering if anyone else has seen similar issues or resorted to
>> that type of thing?
>>
>> Cheers,
>>
>> James
>>
>> James Abley wrote:
>>> Cheers Ralf and Werner,
>>>
>>> That tallies with my understanding.
>>>
>>> Does anyone have real-world examples they can share about complexity
>>> of objects graphs that they have in their domain? One of the
>>> applications I deal with locks a lot of objects (maybe ten objects)
>>> when a root object is loaded.
>>>
>>> Some of this (I believe) is mitigated since some of the domain
>>> objects can be marked in the mapping file as read-only, and so I
>>> would hope that Castor never gets any lock on that; e.g. if one of
>>> the objects references a Country object that is marked as read-only
>>> in the mapping file, any attempt to load something referencing a
>>> Country object will always return that Country object as read-only
>>> and thus no transaction should experience race-conditions on
>>> attempting to gain a lock on a Country object, no matter what
>>> AccessMode is being used by the client transaction.
>>>
>>> But my main concern is whether having such a complex object graph is
>>> damaging to concurrency, and whether I should look at
>>> de-normalisation to flatten it a bit.
>>>
>>> Cheers,
>>>
>>> James
>>>
>>> Werner Guttmann wrote:
>>>> In addition to what Ralf has said, please note that loading objects as
>>>> read-only mode (in one way or the other) will help you improving
>>>> performance as Castor will perform less checks at the end of the
>>>> transaction.
>>>>
>>>> In other words, make sure that you know your domain model, especially
>>>> when it comes down to categorizations such as 'stability',
>>>> 'cacheability', etc.
>>>>
>>>> Regards
>>>> Werner
>>>>
>>>> Ralf Joachim wrote:
>>>>> Hi James,
>>>>>
>>>>> Castor locks the whole object graph from the time when it gets loaded
>>>>> until the end of the transaction which is _db.commit(). If Castor
>>>>> would
>>>>> not lock the whole object graph that could lead to inconsistenties.
>>>>> With
>>>>> the default access mode 'Shared' these locks are handled by Castor
>>>>> internally.
>>>>>
>>>>> As the transaction at your first example is open during 'some long
>>>>> operation' the whole graph gets locked until the end of this
>>>>> transaction.
>>>>>
>>>>> At the second example you have 2 short transaction. The first one
>>>>> loads
>>>>> the object and thereafter releases any locks at first _db.commit().
>>>>> According to this no object is locked during the 'some long
>>>>> operation'.
>>>>> After that operation you start the second transaction which again
>>>>> loads
>>>>> and locks the object including all related ones. Then you do some
>>>>> changes to the objects and commit them. At this commit the changes are
>>>>> written to database and the locks get released again.
>>>>>
>>>>> As the objects are not locked during 'some lock operation' at the
>>>>> second
>>>>> example, you need to be aware that your object may have changed in the
>>>>> meantime.
>>>>>
>>>>> Hope this helps
>>>>> Ralf
>>>>>
>>>>>
>>>>> James Abley schrieb:
>>>>>> Hi,
>>>>>>
>>>>>> I'm trying to understand Castor's locking mechanism for object
>>>>>> graphs.
>>>>>>
>>>>>> Say I have the following classes:
>>>>>>
>>>>>> class Book {
>>>>>>
>>>>>> int id;
>>>>>>
>>>>>> String author;
>>>>>>
>>>>>> ...
>>>>>> }
>>>>>>
>>>>>> class Customer {
>>>>>>
>>>>>> int id;
>>>>>>
>>>>>> // Assume this will be a collection of Books that
>>>>>> // has been browsed by each customer.
>>>>>> Collection booksBrowsed;
>>>>>>
>>>>>> // Assume that this is the transaction history of
>>>>>> // each customer, so a collection of Transaction
>>>>>> // objects
>>>>>> Collection transactions;
>>>>>>
>>>>>> Date lastLoginTime;
>>>>>>
>>>>>> ...
>>>>>> }
>>>>>>
>>>>>> class Transaction {
>>>>>>
>>>>>> int id;
>>>>>>
>>>>>> Date purchaseTime;
>>>>>>
>>>>>> Book item;
>>>>>>
>>>>>> ...
>>>>>> }
>>>>>>
>>>>>> If I have client code that does something like the following:
>>>>>>
>>>>>>
>>>>>> Database db = getDatabase();
>>>>>> db.begin();
>>>>>> db.load(Customer.class, 3, Database.Shared);
>>>>>>
>>>>>> // do some long operation here
>>>>>>
>>>>>> customer.setLastLoginTime(Calendar.getInstance().getTime());
>>>>>> db.commit();
>>>>>> db.close();
>>>>>>
>>>>>>
>>>>>> Is there a lock held on all of the objects in the collections in the
>>>>>> Customer object? Or is a lock only obtained on the Customer object
>>>>>> when
>>>>>> the transaction is ending and Castor can examine each object, see if
>>>>>> it's dirty and thus needs to get a lock to update the object?
>>>>>>
>>>>>> Second related part. I'm very familiar with
>>>>>> http://www.castor.org/jdo-best-practice.html, but I was curious about
>>>>>> another aspect. Assume that I re-write the client to try to
>>>>>> minimize the
>>>>>> transaction:
>>>>>>
>>>>>>
>>>>>> Database db = getDatabase();
>>>>>> db.begin();
>>>>>> db.load(Customer.class, 3, Database.ReadOnly);
>>>>>> db.commit();
>>>>>> db.close();
>>>>>>
>>>>>> // do some long operation here
>>>>>> db.begin();
>>>>>> db.load(Customer.class, 3, Database.Shared);
>>>>>> customer.setLastLoginTime(Calendar.getInstance().getTime());
>>>>>> db.commit();
>>>>>> db.close();
>>>>>>
>>>>>>
>>>>>> Again, what gets locked? Is it the entire object graph, or just the
>>>>>> dirty objects?
>>>>>>
>>>>>> Presumably the latter code sample is the recommended way to go,
>>>>>> irrespective of how the object graph gets locked?
>>>>>>
>>>>>> Cheers,
>>>>>>
>>>>>> James
>>>>>>
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