My Q4 comment may be based more upon my usage of Cayenne 2 than 3. I
know there is some weak reference stuff in 3 that I haven't looked
into yet and perhaps it will automatically clean things up now (which
would be wonderful). I've always taken the approach of evicting
things I no longer wanted so I could control my memory footprint
better. Maybe Andrus/Andrey/etc will chime in with better info here
if I am incorrect on this one.
mrg
On Thu, Apr 8, 2010 at 5:49 PM, Joe Baldwin <jfbaldwi..arthlink.net> wrote:
> Hi Michael,
>
> Thank you for your methodical answers.
>
> RE Q3
> I suspected that this might be one of my problems, and I am trying to redesign so that I only filter & order small result lists.
>
> RE Q4
> Oops! OK, this one totally threw me. Given my understanding of the behavior and usage of the DataContext is somewhere between "wow" to "hmmm, I didn't know that", Perhaps I need to review a primer. :)
>
> But seriously:
> Since I am deploying a web-app, my understanding is that in that type of scenario the container (via the Tomcat CayenneFilter) is instantiating and controlling the DataContext (and I am, presumably now accessing it via BaseContext.getThreadObjectContext();) However, beyond that piece of understanding, I am not sure what to do with it in order to manage objects.
>
> I read your docs once more and it says that the DataContext uses "weak references to store registered objects". I *thought* this meant that (assuming I use the default configuration), that the DataContext would allow the DataObjects to be garbage collected, if there is no reference (Java Reference) and if I did not implement query caching.
>
> I am confused by reading you Q4 comment and then the "Memory Management Strategy" documentation.
>
> (Note: I am attempting to learn more about Cayenne so that I can optimize (and re-factor) my code. I am still uncertain whether I should be implementing caching, not implementing caching, initiating garbage collection (after freeing objects), or just sitting back and letting Cayenne DataContext handle it.)
>
> Thanks,
> Joe
>
>
>
>
> On Apr 8, 2010, at 5:18 PM, Michael Gentry wrote:
>
>> Hi Joe,
>>
>> Assuming 2000 products fetched with a paginated query and a page size
>> of 50, I believe the answers are ...
>>
>> Q1: 2000 hollow objects are created. Cayenne fetches the primary
>> keys of the objects first in a paginated query.
>>
>> Q2: Whichever page (or pages) you access in the paginated list will
>> fault those objects for that page (grouped by 50 at a time) into
>> memory.
>>
>> Q3: If you try to filter or sort in-memory, then it will have to fetch
>> all of the objects. Might be better to re-issue a query to the DB.
>>
>> Q4: If your list pointers go out-of-scope, but the DataContext is
>> still in-scope, then the objects will still be in the DataContext
>> until you evict them.
>>
>> mrg
>>
>>
>> On Thu, Apr 8, 2010 at 4:24 PM, Joe Baldwin <jfbaldwi..arthlink.net> wrote:
>>> Andrus,
>>>
>>> In this same context, I have a question about what behavior I should expect to see.
>>>
>>> Let us assume for this scenario:
>>> 1. a web deployment with Tomcat, typical webstore pattern
>>> 2. 2000-5000 products with an attribute "name"
>>> 3. custom search engine built on top of cayenne
>>> a. mostly standard configuration
>>> b. set PageSize to 50
>>> c. using (presumably) default caching
>>> d. custom factory class method used to create a select query
>>> 4. a user searches for "guitar" substring in the name field
>>>
>>> Questions:
>>> 1. Based on my tests, it appears that "hollow" objects are created but no faults are fired. (true?)
>>> 2. If I display any product data for a subset less than PageSize, then only <PageSize> number of objects are faulted (true ?)
>>> 3. If I execute "filterObjects" or "orderList" on the resulting list, I assume the fault is fired for all objects in the list. (true ?)
>>> 4. What normally happens to these objects if my list pointers go out of scope? (Are they GarbageCollected per Java rules?)
>>>
>>> (Note: I have not been able to get much visibility in understanding (3) & (4), but I think my tests show that 1 & 2 are correct.)
>>> Joe
>>>
>>>
>>>
>>>
>>> On Apr 8, 2010, at 12:42 PM, Andrus Adamchik wrote:
>>>
>>>> BTW, we started on some monitoring hooks inside Cayenne runtime in 3.0 per http://issues.apache.org/jira/browse/CAY-1173 , however then it was decided that it'll work much better with the 3.1 DI-based stack. So this is waiting for its time.
>>>>
>>>> Andrus
>>>>
>>>>
>>>> On Apr 7, 2010, at 6:16 PM, Joe Baldwin wrote:
>>>>
>>>>> I am attempting to do more performance monitoring (with an eye towards optimizing my design & use of DataObject lists and lifetime).
>>>>>
>>>>> The first thing I would like to do is monitor how many DataObjects are created and which JSP session they belong.
>>>>>
>>>>> My idea was to simply create a constructor for the DataObject of interest and place monitoring hooks inside. I would assume that I could also create a finalize method to do similar things.
>>>>>
>>>>> Is this the best way to create custom monitoring using Cayenne DataObjects or is there a better way?
>>>>>
>>>>> (BTW, even after reading the docs, I am still somewhat mystified by how my configuration specifications control the life cycle and performance. So I am hoping these custom hooks will make my design decisions more visible, especially with multiple users.)
>>>>>
>>>>> Thanks,
>>>>> Joe
>>>>>
>>>>>
>>>>
>>>
>>>
>
>
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