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From Andrus Adamchik <and...@objectstyle.org>
Subject Re: Batch iteration
Date Mon, 17 Oct 2016 05:28:25 GMT
Hi Mark,

Scenario B is now the default after a recent change per [1]. We decoupled the transaction
handling open iterator (and all its connections) from any transactions started by context
commits within the iterator. Here is a related mailing list thread [2].

Andrus

[1] https://issues.apache.org/jira/browse/CAY-2111
[2] https://lists.apache.org/thread.html/f1ccb1ac0f0aa974ffe32217fe4fcfe4b3d9a11ef2c8513f2f0e8436@%3Cdev.cayenne.apache.org%3E

> On Oct 16, 2016, at 11:45 PM, Mark Wardle <mark@wardle.org> wrote:
> 
> Thanks John. Interestingly, I did some testing and peer contexts aren’t committed until
the batch iterator JDBC ResultSet is closed at the end of iteration either. This is fine but
for a long running task, I thought that there was a problem (but there wasn’t). I think
the only workarounds are a) to not care [which I think is probably fine or b) do other processing
in another connection. 
> 
> Mark
> 
>> On 15 Oct 2016, at 22:34, John Huss <johnthuss@gmail.com> wrote:
>> 
>> I would use a peer context.
>> 
>> You can create a peer context like this if you runtime has been bound to
>> the current thread using
>> CayenneRuntime.bindThreadInjector(runtime.getInjector())
>> 
>> public static ObjectContext newObjectContext() {
>> ObjectContextFactory factory = CayenneRuntime.getThreadInjector
>> ().getInstance(ObjectContextFactory.class);
>> return (factory != null) ? factory.createContext() : null;
>> }
>> 
>> 
>> 
>> On Sat, Oct 15, 2016 at 2:37 PM Mark Wardle <mark@wardle.org> wrote:
>> 
>>> Sorry… meant to say using Cayenne M4.0.M3…
>>> 
>>> Mark
>>> 
>>>> On 15 Oct 2016, at 20:29, Mark Wardle <mark@wardle.org> wrote:
>>>> 
>>>> I’m using ResultBatchIterator like this:
>>>> 
>>>> Consumer<T> forEach = ...
>>>> try (ResultBatchIterator<T> iterator = query.batchIterator(context,
>>> batchSize)) {
>>>>                     for(List<T> batch : iterator) {
>>>>                             for (T c : batch) {
>>>>                                     forEach.accept(c);
>>>>                             }
>>>>                     }
>>>>             }
>>>> 
>>>> but I also want to do some processing, inserting rows, editing objects
>>> etc. I see lots of SQL in my logs, but the transaction doesn’t get
>>> committed until the batch iterator completes, whether I use
>>> context.commitChanges() or context.performGenericQuery() on some custom SQL
>>> created using SQLTemplate.
>>>> 
>>>> Is there a way of committing the transaction earlier, or should I use a
>>> peer object context? Is there an easy of getting a new peer editing context
>>> given a single object context or do I need to inject a ServerRuntime here?
>>>> 
>>>> Thank you,
>>>> 
>>>> Mark
>>>> 
>>>> 
>>> 
>>> 
> 


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