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Date: Thu, 23 Apr 2009 12:35:49 -0700 (PDT)
From: ArjunReddy <interviewprep@yahoo.com>
To: dev@openjpa.apache.org
Subject: Re: 0penJPA QueryCaching
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Hi Ravi and all,

This is what my code looks like as of now, the retrieving data from the
database part:

final String queryString = "SELECT S FROM StaticContent S JOIN S.aadses
Aads";
Query query = getEntityManager().createQuery(queryString);
List abc  = query.getResultList();

When I debug it, this is what I am getting. Please look at the image
attached.

http://n2.nabble.com/file/n2685502/QueryCache.jpg 

I am able to retrieve everything from the database but the QueryCache is
null. My Persistence.xml file has the three lines

<property name="openjpa.DataCache" value="true"/>
<property name="openjpa.RemoteCommitProvider" value="sjvm"/>
<property name="openjpa.QueryCache" value="true"/>

>From this, maybe can anyone tell me what I am doing wrong?

Thanks.






ArjunReddy wrote:
> 
> Hi Ravi,
> 
> Thanks for replying. I will debug and see... right now I see null next to
> QueryCache but I will check again because I might be doing something wrong
> somewhere. I have two more questions actually.
> 
> 1). When you said the below thing,  I guess you were talking about the
> Query Key right? and if you were, then you were right because I was able
> to retrieve the Query key when I did the below thing.
> 
> *************
> CacheMap cmap =
> ((ConcurrentQueryCache)(OpenJPAPersistence.cast(EntityManager.getEntityManagerFactory()).getQueryResultCache().getDelegate())).getCacheMap();
> 
> The above will give you a map and MAY be cmap.keySet() or
> cmap.getPinnedKeys() should give you set of keys. 
> 
> *************
> 
> 2). In the link you gave me, it says that "The object id list is not
> cached until the list returned at query execution time is fully traversed.
> " Does that mean, I have to like Iterate through the list in order for the
> object ids to get cached?
> 
> Thanks.
> 
> 
> rpalache wrote:
>> 
>> Hi,
>> 
>> Did you get a chance to go through the link I pasted in previous reply:
>> http://openjpa.apache.org/builds/latest/docs/manual/manual.html#ref_guide_cache_query
>> ?
>> 
>> I this openJPA is already doing what ever you are trying to do.
>> So, you do not need to do anything in your application.
>> 
>> You can turn on debugging and see if the call is going to database or the
>> results are returned from cache.
>> 
>> Regards,
>> Ravi.
>> 
>> 
>> ArjunReddy wrote:
>>> 
>>> Hi Ravi,
>>> 
>>> Thanks a lot for replying. I tried doing what you have suggested.
>>> 
>>> This is what I have done.
>>> 
>>> final String queryString = "select P from Parents P";
>>> javax.persistence.Query query =
>>> getEntityManager().createQuery(queryString);
>>> 
>>> QueryResultCacheImpl qcache = (QueryResultCacheImpl)
>>> (OpenJPAPersistence.cast(EntityManager.getEntityManagerFactory())).getQueryResultCache();
>>> // I have casted to QueryResultCacheImpl because
>>> QueryResultCache.getDelegate() is deprecated and the API suggets using
>>> QueryResultCacheImpl.
>>> 
>>> qcache.pin(query); //Pinning the query results to the cache
>>> 
>>> ConcurrentQueryCache cqc = (ConcurrentQueryCache)qcache.getDelegate();
>>> CacheMap cmap = cqc.getCacheMap();
>>> 
>>> Iterator it = cmap.keySet().iterator();   //cmap.getPinnedKeys() is also
>>> returning the same result.
>>> 
>>> while(it.hasNext())
>>> {
>>> System.out.println(it.next());
>>> }
>>> 		
>>> 
>>> And this is the result I got:
>>> 
>>> org.apache.openjpa.datacache.QueryKey@28b16efe[query:[select P from
>>> Parents P],access
>>> path:[com.xyz.Parents],subs:true,ignoreChanges:false,startRange:0,endRange:9223372036854775807,timeout:-1]
>>> 
>>> 
>>> It's returning back the query instead of the query results.:-( I just
>>> want to be able to put my query results (Instances of the Parents Class
>>> which are rows of the Parents table in the database) into the cache and
>>> retrieve it back and see if I am getting them right. Any suggestions as
>>> what I should be doing? Do I have to do something with the DataCache? I
>>> have these defined in my persistence.xml file.
>>> 
>>> <property name="openjpa.DataCache" value="true"/>
>>> <property name="openjpa.RemoteCommitProvider" value="sjvm"/>
>>> <property name="openjpa.QueryCache" value="true"/>
>>> 
>>> Also in my Parents table, I have DataCache defined as follows.
>>> 
>>> @Entity
>>> @DataCache
>>> @Table(name = "PARENTS", schema = "SYSTEM")
>>> public class Parents implements java.io.Serializable {
>>> 
>>> ...
>>> ...
>>> 
>>> }
>>> 
>>> 
>>> Thanks.
>>> 
>>> 
>>> 
>>> rpalache wrote:
>>>> 
>>>> Hi Arjun,
>>>> 
>>>>>>  I am trying to cache the query results generated and later on use
>>>>>> the results from the cache instead of touching the database.
>>>> 
>>>> I think if you enable the querycache properly then openJPA has to do it
>>>> for you.
>>>> 
>>>> Check this link which explains the same:
>>>> http://openjpa.apache.org/builds/latest/docs/manual/manual.html#ref_guide_cache_query
>>>> 
>>>> To enable query cache add the following in the persistence.xml:
>>>> 
>>>> <property name="openjpa.DataCache" value="true"/>
>>>> <property name="openjpa.RemoteCommitProvider" value="sjvm"/>
>>>> <property name="openjpa.QueryCache" value="true"/>
>>>> 
>>>> I hope that answers your question.
>>>> 
>>>> If not, and you are still looking to get a key then may be the
>>>> following will help:
>>>> 
>>>> CacheMap cmap =
>>>> ((ConcurrentQueryCache)(OpenJPAPersistence.cast(EntityManager.getEntityManagerFactory()).getQueryResultCache().getDelegate())).getCacheMap();
>>>> 
>>>> The above will give you a map and MAY be cmap.keySet() or
>>>> cmap.getPinnedKeys() should give you set of keys.
>>>> 
>>>> Regards,
>>>> Ravi.
>>>> 
>>>> 
>>>> 
>>>> 
>>>> 
>>>> ArjunReddy wrote:
>>>>> 
>>>>> Hi All,
>>>>> 
>>>>> I am trying to cache the query results generated and later on use the
>>>>> results from the cache instead of touching the database.
>>>>> 
>>>>> This is what I am doing to put/get the values from the cache.
>>>>> 
>>>>> 
>>>>> **********
>>>>> final String queryString = "select P from Parents P";
>>>>> Query query = getEntityManager().createQuery(queryString);
>>>>> 
>>>>> OpenJPAEntityManagerFactory oemf =
>>>>> OpenJPAPersistence.cast(EntityManagerHelper.getEmf());
>>>>> QueryResultCacheImpl queryResultCache =
>>>>> (QueryResultCacheImpl)oemf.getQueryResultCache();	
>>>>> QueryCache qCache = queryResultCache.getDelegate();
>>>>> 
>>>>> qCache.put(key, (QueryResult)query.getResultList());  // Put into the
>>>>> cache
>>>>> QueryResult cachedItems = qCache.get(key);      // Get from the cache
>>>>> 
>>>>> **********
>>>>> 
>>>>> 
>>>>> The thing I don't understand is how do I get the QueryKey (Referred to
>>>>> as key here in my code) ?
>>>>> 
>>>>> I tried doing this
>>>>> QueryKey key = QueryKey.newInstance(q); but the q here in this line of
>>>>> code is supposed to be of type org.apache.openjpa.kernel.Query?
>>>>> 
>>>>> 
>>>>> 
>>>>> Can anybody help me with this please?
>>>>> 
>>>>> Thanks.
>>>>> 
>>>>> 
>>>> 
>>>> 
>>> 
>>> 
>> 
>> 
> 
> 

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