You are viewing a plain text version of this content. The canonical link for it is here.
Posted to users@openjpa.apache.org by Alexandros Karypidis <ak...@yahoo.gr> on 2008/05/14 11:37:49 UTC
Fetch database changes from external sources
Hi,
First of all, I've done research through the archives for the situation
I am facing and found this:
http://mail-archives.apache.org/mod_mbox/openjpa-users/200706.mbox/%3C7262f25e0706152022u4942a14dkec98e30b520350b7@mail.gmail.com%3E
I am facing the exact problem mentioned in that thread: I need to fetch
an object several times from the database, whose columns are updated
from another program and pick up the changes made by that program.
However, I can't get OpenJPA to re-execute SQL and retrieve the object's
new data from the database.
In the thread of the link I provide, I was lead to believe that
em.refresh(obj) should do the trick. However, OpenJPA does not execute
any SQL (I have SQL=TRACE in the log options and I only see one select
statement) and keeps the old data in the object.
I use OpenJPA release 1.0.2 and the code snippet with which I test is
the following:
=========================================================
EntityManagerFactory emFactory =
Persistence.createEntityManagerFactory(PERSISTENCE_UNIT);
EntityManager em = emFactory.createEntityManager();
Record r = em.find(Record.class, 1);
System.out.println("VALUE: " + r.getStrField());
System.out.print("PRESS ENTER TO REDISPLAY...");
BufferedReader stdin = new BufferedReader(new InputStreamReader(
System.in));
stdin.readLine();
// ------> PROBLEM AREA <------
em.refresh(r); // does not work
// ((OpenJPAEntityManager)em).evict(r); // also does not work
// em.clear(); // works but detaches everything
// em.close(); // ... re-create. works, costs too much
// ------> PROBLEM AREA <------
r = em.find(Record.class, 1);
System.out.println("VALUE: " + r.getStrField());
=========================================================
I change the strField of the "Record" object using a database editor
before I press enter to re-fetch the value.
So, my question is, why does OpenJPA ignore the call to refresh() if the
object is still attached? I don't see it as reasonable to detach all
objects just to pick up a change in the database. I figured it may be a
transaction isolation issue, but then did the following test which also
did not work:
=========================================================
EntityManagerFactory emFactory =
Persistence.createEntityManagerFactory(PERSISTENCE_UNIT);
EntityManager em = emFactory.createEntityManager();
em.getTransaction().begin();
Record r = em.find(Record.class, 1);
System.out.println("VALUE: " + r.getStrField());
em.getTransaction().commit();
System.out.print("PRESS ENTER TO REDISPLAY...");
BufferedReader stdin = new BufferedReader(new InputStreamReader(
System.in));
stdin.readLine();
em.getTransaction().begin();
r = em.find(Record.class, 1);
em.refresh(r);
em.getTransaction().commit();
System.out.println("VALUE: " + r.getStrField());
=========================================================
So even when reading the object through 2 different transactions, I
still can't get its data to be re-fetched...
Funilly enough, if i call rollback() on the transaction, it does work!
However, it seems too much of a kludge to base my solution on that...
Thanks in advace to anyone who takes the time to help out.
Re: Fetch database changes from external sources
Posted by Craig L Russell <Cr...@Sun.COM>.
Hi Alexandros,
Yes, please file a bug and attach your failing code. Extra credit if
you attach a test case in the OpenJPA test case format!
Thanks,
Craig
On May 16, 2008, at 12:18 AM, Alexandros Karypidis wrote:
> I must say this is beginning to look like a bug to me.
>
> The reason is that the code snippet provided works with no problems
> when using Hibernate & Toplink Essentials (it is company policy
> where I work that we stick to pure JPA API and for that reason we
> test our code against OpenJPA, Hibernate & Toplink Essentials).
>
> If somebody doesn't point out something I am doing wrong in the next
> couple of days, I will file a bug report with my snippet as an
> attachment (the code to reproduce this is about 50 lines, including
> the entity class Record, the Main class with the test code and the
> persistence.xml file).
>
> Alexandros Karypidis wrote:
>
>> Hello all,
>> I used the information provided to test the "DataCache" or "2nd-
>> level" cache. The cache doesn't seem to be the problem.
>> I added the following to the persistence.xml:
>> <property name="openjpa.DataCache" value="true" />
>> <property name="openjpa.RemoteCommitProvider" value="sjvm"/>
>> <property name="openjpa.QueryCache" value="true" />
>> <property name="openjpa.Log"
>> value="SQL=TRACE, DataCache=TRACE" />
>> I also tried with the cache disabled (value="false" for
>> openjpa.DataCache) and in both cases refresh() does nothing.
>> With the cache enabled, a cache hit is logged. With the cache
>> disabled, no DataCache logging channel messages are produced. In
>> both cases, no SQL is executed to re-fetch the object.
>> Here is the log output with the cache DISABLED
>> ===========================================================
>> 937 testOpenJPA TRACE [main] openjpa.jdbc.SQL - <t 31365828,
>> conn 25345246> executing prepstmnt 9030750 SELECT t0.strField FROM
>> Record t0 WHERE t0.recId = ? [params=(int) 1]
>> 937 testOpenJPA TRACE [main] openjpa.jdbc.SQL - <t 31365828,
>> conn 25345246> [0 ms] spent
>> RECORD 1 EXISTS, VALUE: Rec 1
>> PRESS ENTER TO REDISPLAY...
>> RECORD 1 EXISTS, VALUE: Rec 1
>> ===========================================================
>> Here is the log output with the cache ENABLED
>> ===========================================================
>> 859 testOpenJPA TRACE [main] openjpa.DataCache - Cache miss
>> while looking up key "1".
>> 922 testOpenJPA TRACE [main] openjpa.jdbc.SQL - <t 23860799,
>> conn 19432672> executing prepstmnt 5324129 SELECT t0.strField FROM
>> Record t0 WHERE t0.recId = ? [params=(int) 1]
>> 922 testOpenJPA TRACE [main] openjpa.jdbc.SQL - <t 23860799,
>> conn 19432672> [0 ms] spent
>> 937 testOpenJPA TRACE [main] openjpa.DataCache - Cache miss
>> while looking up key "1".
>> 937 testOpenJPA TRACE [main] openjpa.DataCache - Put key "1"
>> into cache.
>> 937 testOpenJPA TRACE [main] openjpa.DataCache - Cache hit while
>> looking up key "1".
>> RECORD 1 EXISTS, VALUE: Rec 2
>> PRESS ENTER TO REDISPLAY...
>> 6451 testOpenJPA TRACE [main] openjpa.DataCache - Cache hit
>> while looking up key "1".
>> 6451 testOpenJPA TRACE [main] openjpa.DataCache - Cache hit
>> while looking up key "1".
>> 6467 testOpenJPA TRACE [main] openjpa.DataCache - Cache hit
>> while looking up key "1".
>> RECORD 1 EXISTS, VALUE: Rec 2
>> ===========================================================
>> Drew Lethbridge wrote:
>>> Gday - They're talking about the DataCache. Check out the docs
>>> here:
>>>
>>> http://openjpa.apache.org/docs/latest/manual/ref_guide_caching.html
>>>
>>> In your scenario, you might want to disable the datacache, or
>>> employ datacache timeouts or eviction.
>>>
>>> cheers!
>>>
>>> ..droo.
>>>
>>> On 15/05/2008, at 8:52 PM, Alexandros Karypidis wrote:
>>>
>>>> Hi,
>>>>
>>>> First of all, thanks for the input.
>>>>
>>>> 1) I am not sure what the second-level cache is. Going through
>>>> the user manual and searching the web did not help. All I could
>>>> find that is cache-related are the following properties, which I
>>>> set as follows (hoping that they indeed control the "second-level
>>>> cache"):
>>>>
>>>> <property name="openjpa.DataCache" value="false"/>
>>>> <property name="openjpa.QueryCache" value="false"/>
>>>>
>>>>
>>>> 2) As far as calling evict is concerned, I added these calls
>>>> between the two find() calls:
>>>>
>>>> OpenJPAEntityManagerFactory jemFactory =
>>>> (OpenJPAEntityManagerFactory) emFactory;
>>>> jemFactory.getQueryResultCache().evictAll();
>>>> jemFactory.getStoreCache().evictAll();
>>>> OpenJPAEntityManager jem = (OpenJPAEntityManager) em;
>>>> jem.evictAll(Record.class);
>>>>
>>>> Neither modification helped and as far as the second approach is
>>>> concerned, I would prefer to restrict my code to standard JPA only.
>>>>
>>>> In any case OpenJPA still uses some cache to return the object
>>>> the second time around.
>>>>
>>>> Can you point me towards something more concrete regarding this
>>>> "second level cache" and how to disable it? Is it perhaps
>>>> referred to by some other name? I really couldn't find
>>>> information when web-searching for stuff like "openjpa second
>>>> level cache".
>>>>
>>>> Thanks again for your time.
>>>>
>>>> Craig L Russell wrote:
>>>>
>>>>> Hi,
>>>>> It sounds like you're using the second-level cache which is
>>>>> dutifully returning the current contents that are cached.
>>>>> Have you tried using the evict methods of the second level
>>>>> cache, or disabling it for the application?
>>>>> Craig
>>>>> On May 14, 2008, at 2:37 AM, Alexandros Karypidis wrote:
>>>>>> Hi,
>>>>>>
>>>>>> First of all, I've done research through the archives for the
>>>>>> situation I am facing and found this:
>>>>>>
>>>>>> http://mail-archives.apache.org/mod_mbox/openjpa-users/200706.mbox/%3C7262f25e0706152022u4942a14dkec98e30b520350b7@mail.gmail.com%3E
>>>>>>
>>>>>> I am facing the exact problem mentioned in that thread: I need
>>>>>> to fetch an object several times from the database, whose
>>>>>> columns are updated from another program and pick up the
>>>>>> changes made by that program. However, I can't get OpenJPA to
>>>>>> re-execute SQL and retrieve the object's new data from the
>>>>>> database.
>>>>>>
>>>>>> In the thread of the link I provide, I was lead to believe that
>>>>>> em.refresh(obj) should do the trick. However, OpenJPA does not
>>>>>> execute any SQL (I have SQL=TRACE in the log options and I only
>>>>>> see one select statement) and keeps the old data in the object.
>>>>>>
>>>>>> I use OpenJPA release 1.0.2 and the code snippet with which I
>>>>>> test is the following:
>>>>>>
>>>>>> =========================================================
>>>>>> EntityManagerFactory emFactory =
>>>>>> Persistence.createEntityManagerFactory(PERSISTENCE_UNIT);
>>>>>> EntityManager em = emFactory.createEntityManager();
>>>>>>
>>>>>> Record r = em.find(Record.class, 1);
>>>>>> System.out.println("VALUE: " + r.getStrField());
>>>>>>
>>>>>> System.out.print("PRESS ENTER TO REDISPLAY...");
>>>>>> BufferedReader stdin = new BufferedReader(new InputStreamReader(
>>>>>> System.in));
>>>>>> stdin.readLine();
>>>>>>
>>>>>> // ------> PROBLEM AREA <------
>>>>>> em.refresh(r); // does not work
>>>>>> // ((OpenJPAEntityManager)em).evict(r); // also does not work
>>>>>> // em.clear(); // works but detaches everything
>>>>>> // em.close(); // ... re-create. works, costs too much
>>>>>> // ------> PROBLEM AREA <------
>>>>>>
>>>>>> r = em.find(Record.class, 1);
>>>>>> System.out.println("VALUE: " + r.getStrField());
>>>>>> =========================================================
>>>>>>
>>>>>> I change the strField of the "Record" object using a database
>>>>>> editor before I press enter to re-fetch the value.
>>>>>>
>>>>>> So, my question is, why does OpenJPA ignore the call to
>>>>>> refresh() if the object is still attached? I don't see it as
>>>>>> reasonable to detach all objects just to pick up a change in
>>>>>> the database. I figured it may be a transaction isolation
>>>>>> issue, but then did the following test which also did not work:
>>>>>>
>>>>>> =========================================================
>>>>>> EntityManagerFactory emFactory =
>>>>>> Persistence.createEntityManagerFactory(PERSISTENCE_UNIT);
>>>>>> EntityManager em = emFactory.createEntityManager();
>>>>>>
>>>>>> em.getTransaction().begin();
>>>>>> Record r = em.find(Record.class, 1);
>>>>>> System.out.println("VALUE: " + r.getStrField());
>>>>>> em.getTransaction().commit();
>>>>>>
>>>>>> System.out.print("PRESS ENTER TO REDISPLAY...");
>>>>>> BufferedReader stdin = new BufferedReader(new InputStreamReader(
>>>>>> System.in));
>>>>>> stdin.readLine();
>>>>>>
>>>>>> em.getTransaction().begin();
>>>>>> r = em.find(Record.class, 1);
>>>>>> em.refresh(r);
>>>>>> em.getTransaction().commit();
>>>>>> System.out.println("VALUE: " + r.getStrField());
>>>>>> =========================================================
>>>>>>
>>>>>> So even when reading the object through 2 different
>>>>>> transactions, I still can't get its data to be re-fetched...
>>>>>>
>>>>>> Funilly enough, if i call rollback() on the transaction, it
>>>>>> does work! However, it seems too much of a kludge to base my
>>>>>> solution on that...
>>>>>>
>>>>>> Thanks in advace to anyone who takes the time to help out.
>>>>>>
>>>>> Craig Russell
>>>>> Architect, Sun Java Enterprise System http://java.sun.com/products/jdo
>>>>> 408 276-5638 mailto:Craig.Russell@sun.com
>>>>> P.S. A good JDO? O, Gasp!
>>>>
>>>>
>>>
>>>
>
Craig Russell
Architect, Sun Java Enterprise System http://java.sun.com/products/jdo
408 276-5638 mailto:Craig.Russell@sun.com
P.S. A good JDO? O, Gasp!
Re: Fetch database changes from external sources
Posted by Alexandros Karypidis <ak...@yahoo.gr>.
I must say this is beginning to look like a bug to me.
The reason is that the code snippet provided works with no problems when
using Hibernate & Toplink Essentials (it is company policy where I work
that we stick to pure JPA API and for that reason we test our code
against OpenJPA, Hibernate & Toplink Essentials).
If somebody doesn't point out something I am doing wrong in the next
couple of days, I will file a bug report with my snippet as an
attachment (the code to reproduce this is about 50 lines, including the
entity class Record, the Main class with the test code and the
persistence.xml file).
Alexandros Karypidis wrote:
> Hello all,
>
> I used the information provided to test the "DataCache" or "2nd-level"
> cache. The cache doesn't seem to be the problem.
>
> I added the following to the persistence.xml:
>
> <property name="openjpa.DataCache" value="true" />
> <property name="openjpa.RemoteCommitProvider" value="sjvm"/>
> <property name="openjpa.QueryCache" value="true" />
> <property name="openjpa.Log"
> value="SQL=TRACE, DataCache=TRACE" />
>
> I also tried with the cache disabled (value="false" for
> openjpa.DataCache) and in both cases refresh() does nothing.
>
> With the cache enabled, a cache hit is logged. With the cache disabled,
> no DataCache logging channel messages are produced. In both cases, no
> SQL is executed to re-fetch the object.
>
> Here is the log output with the cache DISABLED
> ===========================================================
> 937 testOpenJPA TRACE [main] openjpa.jdbc.SQL - <t 31365828, conn
> 25345246> executing prepstmnt 9030750 SELECT t0.strField FROM Record t0
> WHERE t0.recId = ? [params=(int) 1]
> 937 testOpenJPA TRACE [main] openjpa.jdbc.SQL - <t 31365828, conn
> 25345246> [0 ms] spent
> RECORD 1 EXISTS, VALUE: Rec 1
> PRESS ENTER TO REDISPLAY...
> RECORD 1 EXISTS, VALUE: Rec 1
> ===========================================================
>
>
> Here is the log output with the cache ENABLED
> ===========================================================
> 859 testOpenJPA TRACE [main] openjpa.DataCache - Cache miss while
> looking up key "1".
> 922 testOpenJPA TRACE [main] openjpa.jdbc.SQL - <t 23860799, conn
> 19432672> executing prepstmnt 5324129 SELECT t0.strField FROM Record t0
> WHERE t0.recId = ? [params=(int) 1]
> 922 testOpenJPA TRACE [main] openjpa.jdbc.SQL - <t 23860799, conn
> 19432672> [0 ms] spent
> 937 testOpenJPA TRACE [main] openjpa.DataCache - Cache miss while
> looking up key "1".
> 937 testOpenJPA TRACE [main] openjpa.DataCache - Put key "1" into cache.
> 937 testOpenJPA TRACE [main] openjpa.DataCache - Cache hit while
> looking up key "1".
> RECORD 1 EXISTS, VALUE: Rec 2
> PRESS ENTER TO REDISPLAY...
> 6451 testOpenJPA TRACE [main] openjpa.DataCache - Cache hit while
> looking up key "1".
> 6451 testOpenJPA TRACE [main] openjpa.DataCache - Cache hit while
> looking up key "1".
> 6467 testOpenJPA TRACE [main] openjpa.DataCache - Cache hit while
> looking up key "1".
> RECORD 1 EXISTS, VALUE: Rec 2
> ===========================================================
>
> Drew Lethbridge wrote:
>
>> Gday - They're talking about the DataCache. Check out the docs here:
>>
>> http://openjpa.apache.org/docs/latest/manual/ref_guide_caching.html
>>
>> In your scenario, you might want to disable the datacache, or employ
>> datacache timeouts or eviction.
>>
>> cheers!
>>
>> ..droo.
>>
>> On 15/05/2008, at 8:52 PM, Alexandros Karypidis wrote:
>>
>>> Hi,
>>>
>>> First of all, thanks for the input.
>>>
>>> 1) I am not sure what the second-level cache is. Going through the
>>> user manual and searching the web did not help. All I could find that
>>> is cache-related are the following properties, which I set as follows
>>> (hoping that they indeed control the "second-level cache"):
>>>
>>> <property name="openjpa.DataCache" value="false"/>
>>> <property name="openjpa.QueryCache" value="false"/>
>>>
>>>
>>> 2) As far as calling evict is concerned, I added these calls between
>>> the two find() calls:
>>>
>>> OpenJPAEntityManagerFactory jemFactory =
>>> (OpenJPAEntityManagerFactory) emFactory;
>>> jemFactory.getQueryResultCache().evictAll();
>>> jemFactory.getStoreCache().evictAll();
>>> OpenJPAEntityManager jem = (OpenJPAEntityManager) em;
>>> jem.evictAll(Record.class);
>>>
>>> Neither modification helped and as far as the second approach is
>>> concerned, I would prefer to restrict my code to standard JPA only.
>>>
>>> In any case OpenJPA still uses some cache to return the object the
>>> second time around.
>>>
>>> Can you point me towards something more concrete regarding this
>>> "second level cache" and how to disable it? Is it perhaps referred to
>>> by some other name? I really couldn't find information when
>>> web-searching for stuff like "openjpa second level cache".
>>>
>>> Thanks again for your time.
>>>
>>> Craig L Russell wrote:
>>>
>>>> Hi,
>>>> It sounds like you're using the second-level cache which is
>>>> dutifully returning the current contents that are cached.
>>>> Have you tried using the evict methods of the second level cache, or
>>>> disabling it for the application?
>>>> Craig
>>>> On May 14, 2008, at 2:37 AM, Alexandros Karypidis wrote:
>>>>> Hi,
>>>>>
>>>>> First of all, I've done research through the archives for the
>>>>> situation I am facing and found this:
>>>>>
>>>>> http://mail-archives.apache.org/mod_mbox/openjpa-users/200706.mbox/%3C7262f25e0706152022u4942a14dkec98e30b520350b7@mail.gmail.com%3E
>>>>>
>>>>>
>>>>> I am facing the exact problem mentioned in that thread: I need to
>>>>> fetch an object several times from the database, whose columns are
>>>>> updated from another program and pick up the changes made by that
>>>>> program. However, I can't get OpenJPA to re-execute SQL and
>>>>> retrieve the object's new data from the database.
>>>>>
>>>>> In the thread of the link I provide, I was lead to believe that
>>>>> em.refresh(obj) should do the trick. However, OpenJPA does not
>>>>> execute any SQL (I have SQL=TRACE in the log options and I only see
>>>>> one select statement) and keeps the old data in the object.
>>>>>
>>>>> I use OpenJPA release 1.0.2 and the code snippet with which I test
>>>>> is the following:
>>>>>
>>>>> =========================================================
>>>>> EntityManagerFactory emFactory =
>>>>> Persistence.createEntityManagerFactory(PERSISTENCE_UNIT);
>>>>> EntityManager em = emFactory.createEntityManager();
>>>>>
>>>>> Record r = em.find(Record.class, 1);
>>>>> System.out.println("VALUE: " + r.getStrField());
>>>>>
>>>>> System.out.print("PRESS ENTER TO REDISPLAY...");
>>>>> BufferedReader stdin = new BufferedReader(new InputStreamReader(
>>>>> System.in));
>>>>> stdin.readLine();
>>>>>
>>>>> // ------> PROBLEM AREA <------
>>>>> em.refresh(r); // does not work
>>>>> // ((OpenJPAEntityManager)em).evict(r); // also does not work
>>>>> // em.clear(); // works but detaches everything
>>>>> // em.close(); // ... re-create. works, costs too much
>>>>> // ------> PROBLEM AREA <------
>>>>>
>>>>> r = em.find(Record.class, 1);
>>>>> System.out.println("VALUE: " + r.getStrField());
>>>>> =========================================================
>>>>>
>>>>> I change the strField of the "Record" object using a database
>>>>> editor before I press enter to re-fetch the value.
>>>>>
>>>>> So, my question is, why does OpenJPA ignore the call to refresh()
>>>>> if the object is still attached? I don't see it as reasonable to
>>>>> detach all objects just to pick up a change in the database. I
>>>>> figured it may be a transaction isolation issue, but then did the
>>>>> following test which also did not work:
>>>>>
>>>>> =========================================================
>>>>> EntityManagerFactory emFactory =
>>>>> Persistence.createEntityManagerFactory(PERSISTENCE_UNIT);
>>>>> EntityManager em = emFactory.createEntityManager();
>>>>>
>>>>> em.getTransaction().begin();
>>>>> Record r = em.find(Record.class, 1);
>>>>> System.out.println("VALUE: " + r.getStrField());
>>>>> em.getTransaction().commit();
>>>>>
>>>>> System.out.print("PRESS ENTER TO REDISPLAY...");
>>>>> BufferedReader stdin = new BufferedReader(new InputStreamReader(
>>>>> System.in));
>>>>> stdin.readLine();
>>>>>
>>>>> em.getTransaction().begin();
>>>>> r = em.find(Record.class, 1);
>>>>> em.refresh(r);
>>>>> em.getTransaction().commit();
>>>>> System.out.println("VALUE: " + r.getStrField());
>>>>> =========================================================
>>>>>
>>>>> So even when reading the object through 2 different transactions, I
>>>>> still can't get its data to be re-fetched...
>>>>>
>>>>> Funilly enough, if i call rollback() on the transaction, it does
>>>>> work! However, it seems too much of a kludge to base my solution on
>>>>> that...
>>>>>
>>>>> Thanks in advace to anyone who takes the time to help out.
>>>>>
>>>> Craig Russell
>>>> Architect, Sun Java Enterprise System http://java.sun.com/products/jdo
>>>> 408 276-5638 mailto:Craig.Russell@sun.com
>>>> P.S. A good JDO? O, Gasp!
>>>
>>>
>>
>>
>
>
Re: Fetch database changes from external sources
Posted by Alexandros Karypidis <ak...@yahoo.gr>.
Hello all,
I used the information provided to test the "DataCache" or "2nd-level"
cache. The cache doesn't seem to be the problem.
I added the following to the persistence.xml:
<property name="openjpa.DataCache" value="true" />
<property name="openjpa.RemoteCommitProvider" value="sjvm"/>
<property name="openjpa.QueryCache" value="true" />
<property name="openjpa.Log"
value="SQL=TRACE, DataCache=TRACE" />
I also tried with the cache disabled (value="false" for
openjpa.DataCache) and in both cases refresh() does nothing.
With the cache enabled, a cache hit is logged. With the cache disabled,
no DataCache logging channel messages are produced. In both cases, no
SQL is executed to re-fetch the object.
Here is the log output with the cache DISABLED
===========================================================
937 testOpenJPA TRACE [main] openjpa.jdbc.SQL - <t 31365828, conn
25345246> executing prepstmnt 9030750 SELECT t0.strField FROM Record t0
WHERE t0.recId = ? [params=(int) 1]
937 testOpenJPA TRACE [main] openjpa.jdbc.SQL - <t 31365828, conn
25345246> [0 ms] spent
RECORD 1 EXISTS, VALUE: Rec 1
PRESS ENTER TO REDISPLAY...
RECORD 1 EXISTS, VALUE: Rec 1
===========================================================
Here is the log output with the cache ENABLED
===========================================================
859 testOpenJPA TRACE [main] openjpa.DataCache - Cache miss while
looking up key "1".
922 testOpenJPA TRACE [main] openjpa.jdbc.SQL - <t 23860799, conn
19432672> executing prepstmnt 5324129 SELECT t0.strField FROM Record t0
WHERE t0.recId = ? [params=(int) 1]
922 testOpenJPA TRACE [main] openjpa.jdbc.SQL - <t 23860799, conn
19432672> [0 ms] spent
937 testOpenJPA TRACE [main] openjpa.DataCache - Cache miss while
looking up key "1".
937 testOpenJPA TRACE [main] openjpa.DataCache - Put key "1" into cache.
937 testOpenJPA TRACE [main] openjpa.DataCache - Cache hit while
looking up key "1".
RECORD 1 EXISTS, VALUE: Rec 2
PRESS ENTER TO REDISPLAY...
6451 testOpenJPA TRACE [main] openjpa.DataCache - Cache hit while
looking up key "1".
6451 testOpenJPA TRACE [main] openjpa.DataCache - Cache hit while
looking up key "1".
6467 testOpenJPA TRACE [main] openjpa.DataCache - Cache hit while
looking up key "1".
RECORD 1 EXISTS, VALUE: Rec 2
===========================================================
Drew Lethbridge wrote:
> Gday - They're talking about the DataCache. Check out the docs here:
>
> http://openjpa.apache.org/docs/latest/manual/ref_guide_caching.html
>
> In your scenario, you might want to disable the datacache, or employ
> datacache timeouts or eviction.
>
> cheers!
>
> ..droo.
>
> On 15/05/2008, at 8:52 PM, Alexandros Karypidis wrote:
>
>> Hi,
>>
>> First of all, thanks for the input.
>>
>> 1) I am not sure what the second-level cache is. Going through the
>> user manual and searching the web did not help. All I could find that
>> is cache-related are the following properties, which I set as follows
>> (hoping that they indeed control the "second-level cache"):
>>
>> <property name="openjpa.DataCache" value="false"/>
>> <property name="openjpa.QueryCache" value="false"/>
>>
>>
>> 2) As far as calling evict is concerned, I added these calls between
>> the two find() calls:
>>
>> OpenJPAEntityManagerFactory jemFactory =
>> (OpenJPAEntityManagerFactory) emFactory;
>> jemFactory.getQueryResultCache().evictAll();
>> jemFactory.getStoreCache().evictAll();
>>
>> OpenJPAEntityManager jem = (OpenJPAEntityManager) em;
>> jem.evictAll(Record.class);
>>
>> Neither modification helped and as far as the second approach is
>> concerned, I would prefer to restrict my code to standard JPA only.
>>
>> In any case OpenJPA still uses some cache to return the object the
>> second time around.
>>
>> Can you point me towards something more concrete regarding this
>> "second level cache" and how to disable it? Is it perhaps referred to
>> by some other name? I really couldn't find information when
>> web-searching for stuff like "openjpa second level cache".
>>
>> Thanks again for your time.
>>
>> Craig L Russell wrote:
>>
>>> Hi,
>>> It sounds like you're using the second-level cache which is dutifully
>>> returning the current contents that are cached.
>>> Have you tried using the evict methods of the second level cache, or
>>> disabling it for the application?
>>> Craig
>>> On May 14, 2008, at 2:37 AM, Alexandros Karypidis wrote:
>>>> Hi,
>>>>
>>>> First of all, I've done research through the archives for the
>>>> situation I am facing and found this:
>>>>
>>>> http://mail-archives.apache.org/mod_mbox/openjpa-users/200706.mbox/%3C7262f25e0706152022u4942a14dkec98e30b520350b7@mail.gmail.com%3E
>>>>
>>>>
>>>> I am facing the exact problem mentioned in that thread: I need to
>>>> fetch an object several times from the database, whose columns are
>>>> updated from another program and pick up the changes made by that
>>>> program. However, I can't get OpenJPA to re-execute SQL and retrieve
>>>> the object's new data from the database.
>>>>
>>>> In the thread of the link I provide, I was lead to believe that
>>>> em.refresh(obj) should do the trick. However, OpenJPA does not
>>>> execute any SQL (I have SQL=TRACE in the log options and I only see
>>>> one select statement) and keeps the old data in the object.
>>>>
>>>> I use OpenJPA release 1.0.2 and the code snippet with which I test
>>>> is the following:
>>>>
>>>> =========================================================
>>>> EntityManagerFactory emFactory =
>>>> Persistence.createEntityManagerFactory(PERSISTENCE_UNIT);
>>>> EntityManager em = emFactory.createEntityManager();
>>>>
>>>> Record r = em.find(Record.class, 1);
>>>> System.out.println("VALUE: " + r.getStrField());
>>>>
>>>> System.out.print("PRESS ENTER TO REDISPLAY...");
>>>> BufferedReader stdin = new BufferedReader(new InputStreamReader(
>>>> System.in));
>>>> stdin.readLine();
>>>>
>>>> // ------> PROBLEM AREA <------
>>>> em.refresh(r); // does not work
>>>> // ((OpenJPAEntityManager)em).evict(r); // also does not work
>>>> // em.clear(); // works but detaches everything
>>>> // em.close(); // ... re-create. works, costs too much
>>>> // ------> PROBLEM AREA <------
>>>>
>>>> r = em.find(Record.class, 1);
>>>> System.out.println("VALUE: " + r.getStrField());
>>>> =========================================================
>>>>
>>>> I change the strField of the "Record" object using a database editor
>>>> before I press enter to re-fetch the value.
>>>>
>>>> So, my question is, why does OpenJPA ignore the call to refresh() if
>>>> the object is still attached? I don't see it as reasonable to detach
>>>> all objects just to pick up a change in the database. I figured it
>>>> may be a transaction isolation issue, but then did the following
>>>> test which also did not work:
>>>>
>>>> =========================================================
>>>> EntityManagerFactory emFactory =
>>>> Persistence.createEntityManagerFactory(PERSISTENCE_UNIT);
>>>> EntityManager em = emFactory.createEntityManager();
>>>>
>>>> em.getTransaction().begin();
>>>> Record r = em.find(Record.class, 1);
>>>> System.out.println("VALUE: " + r.getStrField());
>>>> em.getTransaction().commit();
>>>>
>>>> System.out.print("PRESS ENTER TO REDISPLAY...");
>>>> BufferedReader stdin = new BufferedReader(new InputStreamReader(
>>>> System.in));
>>>> stdin.readLine();
>>>>
>>>> em.getTransaction().begin();
>>>> r = em.find(Record.class, 1);
>>>> em.refresh(r);
>>>> em.getTransaction().commit();
>>>> System.out.println("VALUE: " + r.getStrField());
>>>> =========================================================
>>>>
>>>> So even when reading the object through 2 different transactions, I
>>>> still can't get its data to be re-fetched...
>>>>
>>>> Funilly enough, if i call rollback() on the transaction, it does
>>>> work! However, it seems too much of a kludge to base my solution on
>>>> that...
>>>>
>>>> Thanks in advace to anyone who takes the time to help out.
>>>>
>>> Craig Russell
>>> Architect, Sun Java Enterprise System http://java.sun.com/products/jdo
>>> 408 276-5638 mailto:Craig.Russell@sun.com
>>> P.S. A good JDO? O, Gasp!
>>
>>
>
>
Re: Fetch database changes from external sources
Posted by Drew Lethbridge <dr...@bund.com.au>.
Gday - They're talking about the DataCache. Check out the docs here:
http://openjpa.apache.org/docs/latest/manual/ref_guide_caching.html
In your scenario, you might want to disable the datacache, or employ
datacache timeouts or eviction.
cheers!
.droo.
On 15/05/2008, at 8:52 PM, Alexandros Karypidis wrote:
> Hi,
>
> First of all, thanks for the input.
>
> 1) I am not sure what the second-level cache is. Going through the
> user manual and searching the web did not help. All I could find
> that is cache-related are the following properties, which I set as
> follows (hoping that they indeed control the "second-level cache"):
>
> <property name="openjpa.DataCache" value="false"/>
> <property name="openjpa.QueryCache" value="false"/>
>
>
> 2) As far as calling evict is concerned, I added these calls between
> the two find() calls:
>
> OpenJPAEntityManagerFactory jemFactory =
> (OpenJPAEntityManagerFactory) emFactory;
> jemFactory.getQueryResultCache().evictAll();
> jemFactory.getStoreCache().evictAll();
>
> OpenJPAEntityManager jem = (OpenJPAEntityManager) em;
> jem.evictAll(Record.class);
>
> Neither modification helped and as far as the second approach is
> concerned, I would prefer to restrict my code to standard JPA only.
>
> In any case OpenJPA still uses some cache to return the object the
> second time around.
>
> Can you point me towards something more concrete regarding this
> "second level cache" and how to disable it? Is it perhaps referred
> to by some other name? I really couldn't find information when web-
> searching for stuff like "openjpa second level cache".
>
> Thanks again for your time.
>
> Craig L Russell wrote:
>
>> Hi,
>> It sounds like you're using the second-level cache which is
>> dutifully returning the current contents that are cached.
>> Have you tried using the evict methods of the second level cache,
>> or disabling it for the application?
>> Craig
>> On May 14, 2008, at 2:37 AM, Alexandros Karypidis wrote:
>>> Hi,
>>>
>>> First of all, I've done research through the archives for the
>>> situation I am facing and found this:
>>>
>>> http://mail-archives.apache.org/mod_mbox/openjpa-users/200706.mbox/%3C7262f25e0706152022u4942a14dkec98e30b520350b7@mail.gmail.com%3E
>>>
>>> I am facing the exact problem mentioned in that thread: I need to
>>> fetch an object several times from the database, whose columns are
>>> updated from another program and pick up the changes made by that
>>> program. However, I can't get OpenJPA to re-execute SQL and
>>> retrieve the object's new data from the database.
>>>
>>> In the thread of the link I provide, I was lead to believe that
>>> em.refresh(obj) should do the trick. However, OpenJPA does not
>>> execute any SQL (I have SQL=TRACE in the log options and I only
>>> see one select statement) and keeps the old data in the object.
>>>
>>> I use OpenJPA release 1.0.2 and the code snippet with which I test
>>> is the following:
>>>
>>> =========================================================
>>> EntityManagerFactory emFactory =
>>> Persistence.createEntityManagerFactory(PERSISTENCE_UNIT);
>>> EntityManager em = emFactory.createEntityManager();
>>>
>>> Record r = em.find(Record.class, 1);
>>> System.out.println("VALUE: " + r.getStrField());
>>>
>>> System.out.print("PRESS ENTER TO REDISPLAY...");
>>> BufferedReader stdin = new BufferedReader(new InputStreamReader(
>>> System.in));
>>> stdin.readLine();
>>>
>>> // ------> PROBLEM AREA <------
>>> em.refresh(r); // does not work
>>> // ((OpenJPAEntityManager)em).evict(r); // also does not work
>>> // em.clear(); // works but detaches everything
>>> // em.close(); // ... re-create. works, costs too much
>>> // ------> PROBLEM AREA <------
>>>
>>> r = em.find(Record.class, 1);
>>> System.out.println("VALUE: " + r.getStrField());
>>> =========================================================
>>>
>>> I change the strField of the "Record" object using a database
>>> editor before I press enter to re-fetch the value.
>>>
>>> So, my question is, why does OpenJPA ignore the call to refresh()
>>> if the object is still attached? I don't see it as reasonable to
>>> detach all objects just to pick up a change in the database. I
>>> figured it may be a transaction isolation issue, but then did the
>>> following test which also did not work:
>>>
>>> =========================================================
>>> EntityManagerFactory emFactory =
>>> Persistence.createEntityManagerFactory(PERSISTENCE_UNIT);
>>> EntityManager em = emFactory.createEntityManager();
>>>
>>> em.getTransaction().begin();
>>> Record r = em.find(Record.class, 1);
>>> System.out.println("VALUE: " + r.getStrField());
>>> em.getTransaction().commit();
>>>
>>> System.out.print("PRESS ENTER TO REDISPLAY...");
>>> BufferedReader stdin = new BufferedReader(new InputStreamReader(
>>> System.in));
>>> stdin.readLine();
>>>
>>> em.getTransaction().begin();
>>> r = em.find(Record.class, 1);
>>> em.refresh(r);
>>> em.getTransaction().commit();
>>> System.out.println("VALUE: " + r.getStrField());
>>> =========================================================
>>>
>>> So even when reading the object through 2 different transactions,
>>> I still can't get its data to be re-fetched...
>>>
>>> Funilly enough, if i call rollback() on the transaction, it does
>>> work! However, it seems too much of a kludge to base my solution
>>> on that...
>>>
>>> Thanks in advace to anyone who takes the time to help out.
>>>
>> Craig Russell
>> Architect, Sun Java Enterprise System http://java.sun.com/products/
>> jdo
>> 408 276-5638 mailto:Craig.Russell@sun.com
>> P.S. A good JDO? O, Gasp!
>
>
Re: Fetch database changes from external sources
Posted by Alexandros Karypidis <ak...@yahoo.gr>.
Hi,
First of all, thanks for the input.
1) I am not sure what the second-level cache is. Going through the user
manual and searching the web did not help. All I could find that is
cache-related are the following properties, which I set as follows
(hoping that they indeed control the "second-level cache"):
<property name="openjpa.DataCache" value="false"/>
<property name="openjpa.QueryCache" value="false"/>
2) As far as calling evict is concerned, I added these calls between the
two find() calls:
OpenJPAEntityManagerFactory jemFactory =
(OpenJPAEntityManagerFactory) emFactory;
jemFactory.getQueryResultCache().evictAll();
jemFactory.getStoreCache().evictAll();
OpenJPAEntityManager jem = (OpenJPAEntityManager) em;
jem.evictAll(Record.class);
Neither modification helped and as far as the second approach is
concerned, I would prefer to restrict my code to standard JPA only.
In any case OpenJPA still uses some cache to return the object the
second time around.
Can you point me towards something more concrete regarding this "second
level cache" and how to disable it? Is it perhaps referred to by some
other name? I really couldn't find information when web-searching for
stuff like "openjpa second level cache".
Thanks again for your time.
Craig L Russell wrote:
> Hi,
>
> It sounds like you're using the second-level cache which is dutifully
> returning the current contents that are cached.
>
> Have you tried using the evict methods of the second level cache, or
> disabling it for the application?
>
> Craig
>
> On May 14, 2008, at 2:37 AM, Alexandros Karypidis wrote:
>
>> Hi,
>>
>> First of all, I've done research through the archives for the
>> situation I am facing and found this:
>>
>> http://mail-archives.apache.org/mod_mbox/openjpa-users/200706.mbox/%3C7262f25e0706152022u4942a14dkec98e30b520350b7@mail.gmail.com%3E
>>
>>
>> I am facing the exact problem mentioned in that thread: I need to
>> fetch an object several times from the database, whose columns are
>> updated from another program and pick up the changes made by that
>> program. However, I can't get OpenJPA to re-execute SQL and retrieve
>> the object's new data from the database.
>>
>> In the thread of the link I provide, I was lead to believe that
>> em.refresh(obj) should do the trick. However, OpenJPA does not execute
>> any SQL (I have SQL=TRACE in the log options and I only see one select
>> statement) and keeps the old data in the object.
>>
>> I use OpenJPA release 1.0.2 and the code snippet with which I test is
>> the following:
>>
>> =========================================================
>> EntityManagerFactory emFactory =
>> Persistence.createEntityManagerFactory(PERSISTENCE_UNIT);
>> EntityManager em = emFactory.createEntityManager();
>>
>> Record r = em.find(Record.class, 1);
>> System.out.println("VALUE: " + r.getStrField());
>>
>> System.out.print("PRESS ENTER TO REDISPLAY...");
>> BufferedReader stdin = new BufferedReader(new InputStreamReader(
>> System.in));
>> stdin.readLine();
>>
>> // ------> PROBLEM AREA <------
>> em.refresh(r); // does not work
>> // ((OpenJPAEntityManager)em).evict(r); // also does not work
>> // em.clear(); // works but detaches everything
>> // em.close(); // ... re-create. works, costs too much
>> // ------> PROBLEM AREA <------
>>
>> r = em.find(Record.class, 1);
>> System.out.println("VALUE: " + r.getStrField());
>> =========================================================
>>
>> I change the strField of the "Record" object using a database editor
>> before I press enter to re-fetch the value.
>>
>> So, my question is, why does OpenJPA ignore the call to refresh() if
>> the object is still attached? I don't see it as reasonable to detach
>> all objects just to pick up a change in the database. I figured it may
>> be a transaction isolation issue, but then did the following test
>> which also did not work:
>>
>> =========================================================
>> EntityManagerFactory emFactory =
>> Persistence.createEntityManagerFactory(PERSISTENCE_UNIT);
>> EntityManager em = emFactory.createEntityManager();
>>
>> em.getTransaction().begin();
>> Record r = em.find(Record.class, 1);
>> System.out.println("VALUE: " + r.getStrField());
>> em.getTransaction().commit();
>>
>> System.out.print("PRESS ENTER TO REDISPLAY...");
>> BufferedReader stdin = new BufferedReader(new InputStreamReader(
>> System.in));
>> stdin.readLine();
>>
>> em.getTransaction().begin();
>> r = em.find(Record.class, 1);
>> em.refresh(r);
>> em.getTransaction().commit();
>> System.out.println("VALUE: " + r.getStrField());
>> =========================================================
>>
>> So even when reading the object through 2 different transactions, I
>> still can't get its data to be re-fetched...
>>
>> Funilly enough, if i call rollback() on the transaction, it does work!
>> However, it seems too much of a kludge to base my solution on that...
>>
>> Thanks in advace to anyone who takes the time to help out.
>>
>
> Craig Russell
> Architect, Sun Java Enterprise System http://java.sun.com/products/jdo
> 408 276-5638 mailto:Craig.Russell@sun.com
> P.S. A good JDO? O, Gasp!
>
Re: Fetch database changes from external sources
Posted by Craig L Russell <Cr...@Sun.COM>.
Hi,
It sounds like you're using the second-level cache which is dutifully
returning the current contents that are cached.
Have you tried using the evict methods of the second level cache, or
disabling it for the application?
Craig
On May 14, 2008, at 2:37 AM, Alexandros Karypidis wrote:
> Hi,
>
> First of all, I've done research through the archives for the
> situation I am facing and found this:
>
> http://mail-archives.apache.org/mod_mbox/openjpa-users/200706.mbox/%3C7262f25e0706152022u4942a14dkec98e30b520350b7@mail.gmail.com%3E
>
> I am facing the exact problem mentioned in that thread: I need to
> fetch an object several times from the database, whose columns are
> updated from another program and pick up the changes made by that
> program. However, I can't get OpenJPA to re-execute SQL and retrieve
> the object's new data from the database.
>
> In the thread of the link I provide, I was lead to believe that
> em.refresh(obj) should do the trick. However, OpenJPA does not
> execute any SQL (I have SQL=TRACE in the log options and I only see
> one select statement) and keeps the old data in the object.
>
> I use OpenJPA release 1.0.2 and the code snippet with which I test
> is the following:
>
> =========================================================
> EntityManagerFactory emFactory =
> Persistence.createEntityManagerFactory(PERSISTENCE_UNIT);
> EntityManager em = emFactory.createEntityManager();
>
> Record r = em.find(Record.class, 1);
> System.out.println("VALUE: " + r.getStrField());
>
> System.out.print("PRESS ENTER TO REDISPLAY...");
> BufferedReader stdin = new BufferedReader(new InputStreamReader(
> System.in));
> stdin.readLine();
>
> // ------> PROBLEM AREA <------
> em.refresh(r); // does not work
> // ((OpenJPAEntityManager)em).evict(r); // also does not work
> // em.clear(); // works but detaches everything
> // em.close(); // ... re-create. works, costs too much
> // ------> PROBLEM AREA <------
>
> r = em.find(Record.class, 1);
> System.out.println("VALUE: " + r.getStrField());
> =========================================================
>
> I change the strField of the "Record" object using a database editor
> before I press enter to re-fetch the value.
>
> So, my question is, why does OpenJPA ignore the call to refresh() if
> the object is still attached? I don't see it as reasonable to detach
> all objects just to pick up a change in the database. I figured it
> may be a transaction isolation issue, but then did the following
> test which also did not work:
>
> =========================================================
> EntityManagerFactory emFactory =
> Persistence.createEntityManagerFactory(PERSISTENCE_UNIT);
> EntityManager em = emFactory.createEntityManager();
>
> em.getTransaction().begin();
> Record r = em.find(Record.class, 1);
> System.out.println("VALUE: " + r.getStrField());
> em.getTransaction().commit();
>
> System.out.print("PRESS ENTER TO REDISPLAY...");
> BufferedReader stdin = new BufferedReader(new InputStreamReader(
> System.in));
> stdin.readLine();
>
> em.getTransaction().begin();
> r = em.find(Record.class, 1);
> em.refresh(r);
> em.getTransaction().commit();
> System.out.println("VALUE: " + r.getStrField());
> =========================================================
>
> So even when reading the object through 2 different transactions, I
> still can't get its data to be re-fetched...
>
> Funilly enough, if i call rollback() on the transaction, it does
> work! However, it seems too much of a kludge to base my solution on
> that...
>
> Thanks in advace to anyone who takes the time to help out.
>
Craig Russell
Architect, Sun Java Enterprise System http://java.sun.com/products/jdo
408 276-5638 mailto:Craig.Russell@sun.com
P.S. A good JDO? O, Gasp!
Re: Fetch database changes from external sources
Posted by Alexandros Karypidis <ak...@yahoo.gr>.
I would like to add that I am using OpenJPA in standalone mode.
Also, I was thinking about the PersistenceContextType and that it may be
EXTENDED (which may be related to my woes), but I can't seem to find a
createEntityManager(PersistencContextType type) method in the factory.
Is that not part of the standard?