repost:
So regarding Collection Proxy Locking, I think there is a reasonable solution:
1. Maintain a list of information about Collections that are locked as proxies, in
this list put:
a. A query that will return the list of id's for objects that are locked, ie
"SELECT ... FROM FOO_TABLE WHERE PARENT_ID = BAR", decompose this from
string based representation for better performance.
2. During the locking phase of an object, do the following:
a. Check if the CollectionProxyLockedList has any elements
b. Check if the CollectionProxyLockedList has any elements for this Table type
(FOO_TABLE)
b. Check if the object being locked participates in the many side of a
one-to-many.
c. if there exists a locked collection on the table you want to lock the
object for, execute the query that checks if this object is locked, ie
"SELECT COUNT(*) FROM FOO_TABLE WHERE PARENT_ID IN <ALL PARENT ID's
FOR COLLECTIONS MAPPED TO THIS TABLE THAT HAVE PROXIED COLLECTIONS LOCKED> AND
ID=<requested for lock object id>"
d. if result is not 0, there is a lock on that object.
I think this should be reasonably fast if implemented correctly, and could still be
implemented to work with the persistent lock map impl as well as the in-memory lock
map. It would depend on users knowing how their application works, and then
configuring proxied collections properly.
thoughts?
-----Original Message-----
From: Mahler Thomas [mailto:[EMAIL PROTECTED]]
Sent: Wednesday, September 11, 2002 12:27 AM
To: 'OJB Users List'
Subject: AW: ODMG and locking
Hi Phil,
As Charles already mentioned this is a known issue.
The solution we have in mind is to provide a flag that will allow you to use
explicit locking, without scanning of object graphs etc.
This is the next thing I'm going to implement. I hope to get it done within
a the next 2 weeks.
thanks for your patience,
Thomas
> -----Urspr�ngliche Nachricht-----
> Von: Phil Warrick [mailto:[EMAIL PROTECTED]]
> Gesendet: Dienstag, 10. September 2002 18:25
> An: OJB Users List
> Betreff: ODMG and locking
>
>
> Hello,
>
> I've run into the problem of ODMG locking overhead and would
> like some
> ideas about best OJB practices to deal with it (~4 minutes to
> retrieve
> one object means something has to be done). I've seen bits
> and pieces
> of discussion related to this issue, so forgive me if I'm bringing up
> old stuff.
>
> If I understand correctly, enforcing persistence by
> reachability means
> that once one object is retrieved, this object and all others in the
> associated graph are locked.
>
> Does the locking extend to the contents of proxy references and proxy
> collections?
>
> What are the best ways to limit the extent of the locking in a large
> graph? For example, say some classes have instances that are
> created/updated often and these classes refers to other
> classes that are
> much more static. If the graph of the static objects is
> large, locking
> is a big problem. How can one keep the link between these
> classes and
> not suffer the lock overhead?
>
> Your responses would be most appreciated.
>
> Phil
>
>
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