Hi, After some investigation it comes down to two problems
1) An example. I have 2 libraries. One library calls the other one. The first one is using the iterated query to get some data. It will call the second library to process the data. This second library however is not aware of a iterated query being used and it simply creates a new DataContext and will commit it when it sees fit. But it doesn't get a new transaction as there is already one bound to the thread. This would effectively mean that every application that uses cayenne has to check the bound transaction and if it exists create a new one and restore it later (assuming he wants its own transaction). This is a weird situation. 2) An example. I have 2 libraries. One library calls the other one. The first one is setting a task record to 'in progress'. Then it calls the second library. The second one is using an iterated query but it is wrapped in an Iterator such that the caller doesn't see the details. This however means that when an exception occurs that the ResultIterator is not closed. This means that the transaction is not unbound and as such never committed. The commit on the trasaction created by the calling library then also doesn't work. Now you could say that this is a design flaw. I partly agree. I should not wrap the ResultIterator in an iterator as this prevents access to the close method. So should I create a new iterator class with the close method and let this one 'bleed' through to the user? This also seems not a nice solution to me. An thoughts? tx Hans On 1/5/11 7:29 PM, Andrus Adamchik wrote:
Haven't thought about this scenario deeply... How about this: In the simplest case you can keep your changes in the DataContext while iterating over the result (DataContext by itself is not permanently bound to a transaction). And then commit them after iteration is finished. This will work if only some objects have changes and you have enough memory to keep them in a DataContext. Or if you need to flush data to DB in smaller chunks without committing a DB transaction, you can still do it by temporary re-bidning your own transaction to the current thread for the duration of commit, and then restoring it to the iterated query transaction when update is done. Andrus On Dec 29, 2010, at 3:25 PM, Hans Pikkemaat wrote:Hi, I'm using an iterated query to process a huge amount of data which cannot be loaded at once. This query creates its own transaction and binds it to the current thread. This means that when I process the data I received from the iterated query all queries use the transaction created by the iterated query. So any updates executed while the iterated query is running will be committed when the iterated query (actually the Result Iterator) is closed. So the iterator is committing the updates for me what I don't want. I know I can create my own transaction but this doesn't help me. I want to be able to create a transaction and within that transaction I want to run the iterated query and while in the query I want to do updates which are committed when I commit my own transaction. Question: Is there a way to prevent the iterated query to 'hyjack' my transaction? pseudo code create datacontext (my transaction) run iterated query (overrides my transaction) process data do some updates (will use the transaction of the iterator) close iterator (will commit my updates. I don't want this) commit my updates (does nothing as its already committed by the iterator) tx Hans PS: I'm using cayenne 2.0.4
