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From Evgeny Ryabitskiy <evgeny.ryabits...@gmail.com>
Subject Re: Cayenne 3.0 cache RefreshQuery for NamedQuery
Date Thu, 22 Jul 2010 21:36:19 GMT
2010/7/21 Andrus Adamchik <andrus@objectstyle.org>:
> I totally understand what you are saying about simplicity and certainly
> don't want to sacrifice any of that here. Along these lines I am trying to
> avoid adding special cases of mapping that are not generic enough, which
> actually makes things more complex in the end. Both for us, as we end up
> with too many if/else cross-feature interactions throughout the stack, and
> for our users, as there are too many abstractions and no consistent picture
> of what the framework is about. We tried hard to get rid of a few of those
> in 3.0, such as "derived DbEntities" and will keep doing it in 3.1 (such as
> merging EJBQL and SelectQuery). So I am being extra cautious now to avoid
> the next round  :-) At the same time this shouldn't stop us from trying and
> experimenting with things of course...

It's great to have like-minded person in you :)

>. Performance... Indeed, there is some overhead
> looking up entity listeners. I think it will be much much less with query
> listeners - a single HashMap lookup vs. recursively scanning through the
> entity class hierarchy (which we should optimize too by caching all
> listeners per class hierarchy).

I'm totally (100%) against losing Performance even on 5% even on 1%!!!
So I am against adding listeners here....


>BTW, with listeners you may even optimize
> your 8000 SQLTemplates per transaction scenario, as a listener can batch
> groups to refresh and then refresh them at once at the end of the
> transaction, instead of doing it 8000 times.

Not sure if I understand you... If you are talking about group caching
per call(transaction) - it's not my case. Queries are mostly different
and even same queries could/should return different results because
there could be several inserts/updates between.... Try to catch this
problem in 32000+ line log :) Really not ready to try it...

My caching in first way will be used only for dictionary tables in
SHARED cache and not refreshed too often (not more then once per day).
In second I may try Context cashing for tables that are not changed
per operation(transaction). But it's not near feature optimization....


> The second aspect is simplicity of mapping. Current entity listeners mapping
> is not entirely intuitive (mainly because of its JPA roots with insane
> hierarchical listener rules), and I'd like to simplify that in the future.
> One angle of attack is to start using annotations for callbacks/listeners,
> so that we don't have to map the method names in the Modeler at all. For
> queries it will be simpler even without annotations, as initially we will
> have a single event type ("post-commit"), and you will have to simply
> specify the listener class (or multiple classes) per query and that's it.
>
> So do you think this is still too complex? (This is an honest question...
> when I looked closer at the problem, I don't feel that much opposed to your
> original solution, just trying to see if we can reuse an abstraction that we
> already have).

Honestly still don't wish to use listeners... in my case it will be
heap of listeners at one place. Even it will be several heaps (from
several modules) which should be collected in one.... Sory can't find
any place for this feature.... :(
 For me it's much better to have such things at local places in code
(like it's can be done now) or in SQLTemplates (like was in my idea).


May be I will try explain my point of view.... So you will see it with
my eyes :)
Imagine:
1) You are going to Modeller
2) Creating simple Row SQL
3) See options about cache: NO Cache, LOCAL Cache, SHARED Cache

Cool! But it's actualy only for SELECT queries. So what with
INSERT/UPDATE/DELETE  queries (that could be also in template)?
For INSERT/UPDATE/DELETE queries such options have no sense.
But.... They could invalidate cache!!!.. It's actually what they
usually does... Why not to extend this options for
INSERT/UPDATE/DELETE in reverse effect...?
So on SELECT we are caching on INSERT/UPDATE/DELETE  we are refreshing
cache... for me it looks very intuitive and logically......


If still not looks logically for you, then it was bad idea.... )



 Evgeny.



> On Jul 20, 2010, at 10:58 PM, Evgeny Ryabitskiy wrote:
>>
>> 2010/7/20 Andrus Adamchik <andrus@objectstyle.org>:
>>>
>>> So how do we solve it? I would like to avoid tying a "query execution
>>> event"
>>> directly to cache refresh. Maybe instead we can attach this new type of
>>> events (at the beginning EJBQL/SQLTemplate events) to the same set of
>>> listeners as entity events? A listener can be defined to do a cache
>>> refresh
>>> of a certain group, or do something else entirely. Even the events can be
>>> defined in terms of specific entities. E.g. "query X generates
>>> 'post-update'
>>> event for entity Y" ... or not :-) Something to think about...
>>
>> I am glad that it gave us some "food for brain"! :)
>>
>> But I should remind that my issue wasn't about adding SQLTemplate
>> events...
>> I just show that events can't solve this issue. But even if it could,
>> I'm not sure what I would prefer... configuring listeners on
>> SQLTemplate events or just put "removeCacheGroup" method invocation
>> after each "performNotSelectionQuery".
>> Second one seems even easier... and already available in 3.0...
>>
>> One more thing... would we pay some CPU cost on SQLTemplate event
>> initialization? Like iterating through Collection of Listeners...
>> One business operation could generate ~ 8000 SQLTemplate queries. I
>> don't wish to lose here any performance!....
>> Actually I'm looking for any solution that could speed up them.... but
>> it's another topic...
>>
>> Evgeny.
>>
>> P.S.
>> And one more off-top :)
>> For me: Most advantage of Cayenne above so popular Hibernate is it
>> simplicity. For simple things it does simple actions! And doest it
>> fast!
>> Maybe this project should stay on this way, and not to follow it's
>> neighbor overloading every operation with lot's of features just to be
>> super flexible super universal....?
>> Please, don't think that I am trying to dictate you where to lead
>> Cayenne. Just some opinion :)
>>
>>
>>
>>
>>
>>
>>
>>
>>>
>>> On Jul 20, 2010, at 5:51 PM, Evgeny Ryabitskiy wrote:
>>>>
>>>> Thx, for your reply.
>>>>
>>>> Now, I see only events related with Entity manipulations. Is there a
>>>> way to add listener for NamedQuery execution?
>>>>
>>>> As I understand Event listeners could be configured in some "static"
>>>> section while Cayenne configuration initialization...
>>>> It's not so bad until you have ~30 cashed tables and almost 100-200
>>>> queries to that tables.
>>>> Problem that it's had to monitor that all Update queries got their
>>>> listener when this information is decomposed between Java Code and XML
>>>> with SQL Templates.
>>>>
>>>> Idea was to create such architecture where "Persistent" (DBMS related)
>>>> layer is separate from Java logic and caching could be handled by only
>>>> map.xml changes.
>>>>
>>>> Evgeny.
>>>
>>>
>>
>
>

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