Named PM in addition to named PMF

[Christian Ernst <ce...@versant.com>]

Hi JDO friends !

Following the discussion about named PMF,
i would like to suggest to add also a name to PM.

I think there are cases where it would be helpful to have a named PM.
For Example:
A named PM allows to track its PM / TXN via logging up to the Database 
Server ( assuming the Database Server allows somehow named TXN )
It would allow explicit lookup via name from the PMF of a PM like
JDOHelper.getPersistenceManagerFactoryByName("logistic").get.getPersistenceManagerByName("warehouseexit");


Versant has already a vendor extension to set the name of the PM.
The name is used in Backend Transaction and allows Customer
much easier to track problematic long running or blocking Transactions
and find the corresponding code in there Application.

cheers
Christian

RE: Named PM in addition to named PMF

[Matthew Adams <ma...@xcalia.com>]

Hi Christian,

This smells like the userObject property/map allowable on the PM that
was present in JDO 1.0 and expanded in JDO 2.0.  The only difference, if
I understand what you're saying, is that you would be able to get a PM
from a PMF by userObject, yes?

If so, this would require a method overload on PMF:

PersistenceManager getPersistenceManagerByUserObject(Object userObject);

Or something like this.  Questions:

* This would require that all PMFs maintain a map of PMs by userObject,
yes?  Is that reasonable to expect from implementations, or do we
consider another JDO option like
"javax.jdo.option.SupportsKeyedPersistenceManagers"?
* What would the PMF return if there were no userObject at that key in
the map?  Null?
* How does this complement or conflict with the proposed PMF method
getPersistenceManagerProxy()?  Is that sufficient?  They smell kind of
similar to me.

-matthew


>-----Original Message-----
>From: Christian Ernst [mailto:cernst@versant.com] 
>Sent: Wednesday, February 28, 2007 10:40 PM
>To: JDO Expert Group
>Cc: jdo-dev@db.apache.org
>Subject: Named PM in addition to named PMF
>
>Hi JDO friends !
>
>Following the discussion about named PMF,
>i would like to suggest to add also a name to PM.
>
>I think there are cases where it would be helpful to have a named PM.
>For Example:
>A named PM allows to track its PM / TXN via logging up to the Database 
>Server ( assuming the Database Server allows somehow named TXN )
>It would allow explicit lookup via name from the PMF of a PM like
>JDOHelper.getPersistenceManagerFactoryByName("logistic").get.ge
>tPersistenceManagerByName("warehouseexit");
>
>
>Versant has already a vendor extension to set the name of the PM.
>The name is used in Backend Transaction and allows Customer
>much easier to track problematic long running or blocking Transactions
>and find the corresponding code in there Application.
>
>cheers
>Christian
>
>
>
>
>