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From Jeff de Vries <>
Subject Re: Caching problem?
Date Sat, 20 May 2006 04:25:23 GMT
Named queries? - No (is there a problem with named queries?)
Same context? - Maybe.  This is a web app, and the alert is created 
during one http request, while the check is on a subsequent http 
request.  Since the data context is being bound to the thread, it would 
depend on whether the same thread handled both requests.  How can I 
create a new (different) data context if I want to make sure it is 
different than the original data context?  BTW, this problem is 
repeatable, so if the problem is using the same data context, then it 
would appear that the same thread is being used for both http requests.

Marcin Skladaniec wrote:
> I'll ask few questions, just to be sure:
> - are you using named queries (ie. when fetching the alerts)
> - are you using the same context when creating alert and when checking 
> for the alerts ?
> If the latter try to use different context. And to be 100% sure in the 
> second query do query.setCachingPolicy(SelectQuery.NO_CHACHE);
> See if that helps.
> Regards
> Marcin
> On 20/05/2006, at 11:35 AM, Jeff de Vries wrote:
>> It didn't make any difference.  (I was so sure it *would* make a 
>> difference I ran it three times and double-checked everything each 
>> time).
>> Looking at the SQL log, it looks like I oversimplified the 
>> description of the problem (sorry).  There is actual another table 
>> involved, Listing, and the status that is being updated is in 
>> Listing, not in Alert, though the Listing is being accessed through 
>> the Alert (Alert has a foreign key referencing the Listing).  So, let 
>> me try again to describe the sequence of steps that are used to 
>> update the database:
>> 1)  Using a given Listing, we SELECT all Alerts that refer to that 
>> Listing. (In the case I'm looking at there is only one Alert).
>> 2)  Start transaction (i.e. there is a (unnecessary?) commit after 
>> the previous SELECT)
>> 3)  INSERT a new Alert that references the existing Listing (note 
>> that at this point the Listing has not been updated yet, i.e. it 
>> still has the old status) and the Person the Alert is addressed to.
>> 4)  UPDATE the first Alert to indicate it has been processed (i.e. 
>> set a 'seen' column to 'true')
>> 5)  UPDATE the status in the Listing to the new status (this is the 
>> thing we're seeing the old version of later)
>> 6)  COMMIT changes.
>> Later, we do the following:
>> 1)  SELECT all Alerts addressed to this Person (which includes the 
>> new Alert created in step 3 above; this is also the query to which we 
>> added setRefreshingObjects = true, which now looks unnecessary since 
>> we did get the new Alert even before making that change)
>> 2)  For each Alert, display the status of the Listing referenced by 
>> that Alert.  Note that at this point in the SQL log I don't see any 
>> SELECT statements trying to retrieve Listing data, so I'm guessing 
>> Cayenne thinks it already knows all the associated Listings and their 
>> statuses.  It looks like it is the relationship between Alert and 
>> Listing that needs to be refreshed?
>> 3)  The status for the Listing associated with the new Alert still 
>> shows the value it had before it was updated in step 5 above.
>> So, is it possible that when the new Alert is created it is pointing 
>> at the original version of the Listing (I'm talking about the 
>> in-memory objects, not the rows out in the database), but when the 
>> Listing is updated the in-cache version isn't getting updated?  Or 
>> the in-cache version is getting updated, but the Alert is pointing at 
>> a stale Listing object?
>> Thanks for the help!
>> Jeff
>> Marcin Skladaniec wrote:
>>> You can try:
>>> DataContext dc = DataContext.getThreadDataContext();
>>> SelectQuery query = new SelectQuery(alert_subclass);
>>> ...
>>> query.setRefreshingObjects(true);
>>> ...
>>> List result = dc.performQuery(query);
>>> Regards
>>> Marcin
>>> On 20/05/2006, at 8:05 AM, Jeff de Vries wrote:
>>>> I get the following compile error (I'm using Cayenne 1.2):
>>>>   The method performQuery(Query) in the type DataContext is not 
>>>> applicable for the arguments (SelectQuery, boolean)
>>>> I tried to find something equivalent for Cayenne 1.2 but didn't 
>>>> recognize anything.
>>>> Gentry, Michael (Contractor) wrote:
>>>>> Could you try: List result = dc.performQuery(query, true); And see 
>>>>> if it works better? Thanks, /dev/mrg -----Original Message----- 
>>>>> From: Jeff de Vries [] Sent: Friday, May 
>>>>> 19, 2006 12:18 PM To: Subject: 
>>>>> Re: Caching problem? It's pretty straightforward. In the following 
>>>>> code Person is the parent, and Alert is the child. There are 
>>>>> actually many Alert classes (I'm using Cayenne STI), so the 
>>>>> specific Alert class we're interested in is passed as a parameter. 
>>>>> Also, I forgot to mention that if we shut everything down, and 
>>>>> then restart, we do see the modified status (presumably because 
>>>>> Cayenne really had to go back to the database to get the data for 
>>>>> the child list). /** * Finds all Alerts of the given type sent to 
>>>>> the given person * * @param person * Person to find Alerts for * 
>>>>> @param include_hidden * If true, include hidden alerts as well * 
>>>>> @param alert_subclass * Class of alert to search for * @return 
>>>>> List of alert objects, of given type, for the given person */ 
>>>>> protected static List findFor(Person person, boolean 
>>>>> include_hidden, Class alert_subclass) { DataContext dc = 
>>>>> DataContext.getThreadDataContext(); SelectQuery query = new 
>>>>> SelectQuery(alert_subclass); 
>>>>> query.setQualifier(ExpressionFactory.matchExp("toReceiver", 
>>>>> person)); query.andQualifier(ExpressionFactory.matchExp("deleted", 
>>>>> new Boolean (false))); if (!include_hidden) 
>>>>> query.andQualifier(ExpressionFactory.matchExp("hidden",new Boolean 
>>>>> (false))); query.addOrdering("createDate",false); List result = 
>>>>> dc.performQuery(query); return result; } On May 19, 2006, at 6:05 
>>>>> AM, Gentry, Michael ((Contractor)) wrote:
>>>>>> Jeff, could you post the code where you are doing the second 
>>>>>> query? Thanks! /dev/mrg -----Original Message----- From: Jeff de

>>>>>> Vries [] Sent: Friday, May 19, 2006 
>>>>>> 12:09 AM To: Subject: Caching 
>>>>>> problem? Simplified version: I have a parent table and a child 
>>>>>> table, where the child table has a parent_id column and a status

>>>>>> column. I change the status in one of the child records and 
>>>>>> commit the change. Later, I ask for the child records for the 
>>>>>> given parent record, but the child record that I get back on 
>>>>>> which I changed the status still has the *old* status instead of

>>>>>> the new status. If I look at the database, the child record does

>>>>>> have the new status (and in fact I can see the update and commit

>>>>>> as soon as I commit the child record change). Why is the parent 
>>>>>> still seeing the old child status? An additional note is that I'm

>>>>>> not using parent.getChildArray() but rather a SelectQuery(Child)

>>>>>> that matches toParent to the parent I'm interested in. (This is 
>>>>>> in Cayenne 1.2B2 using PostgreSQL 8.1) Thanks, Jeff

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