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From "David Wisneski" <wisnes...@gmail.com>
Subject Re: [jira] Commented: (OPENJPA-182) db2 update lock syntax WITH <isolation> USE AND KEEP UPDATE LOCKS
Date Thu, 05 Apr 2007 18:35:08 GMT
Patrick,

We were unaware that fetch plan properties could be set as Hints.  Now
that we look at the code we see this,  but we did not find this when
we read the OpenJPA documentation.  The only hint we found in the
documentation was the OracleSelectHint and so our design was based on
how OracleSelectHint was implemented.  OracleSelectHint is not
implemented as a FetchPlan property.

Why don't you integrate your patch and then we will rerun our tests to
make sure the function works as we had originally intended.


On 4/5/07, Patrick Linskey (JIRA) <jira@apache.org> wrote:
>
>    [ https://issues.apache.org/jira/browse/OPENJPA-182?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12487046
]
>
> Patrick Linskey commented on OPENJPA-182:
> -----------------------------------------
>
> > > Hopefully, this will be useful for applications where there are "hot" tables
> > > that require pessimistic locking even though the rest of the application
> > > does better with optimistic.
> >
> > That's what our lock levels and lock APIs are for. I'm still not clear on what this
is
> > adding to the mix for most DBs.
>
> Not really -- the lock levels allow the user to configure how locking should happen,
not what the isolation level should be for the locks.
>
> I don't know about what levels of support non-DB2 databases have for per-query isolation
level configuration. Does anyone have any experience with this in other databases?
>
> Oh, and regardless, we should change the base DBDictionary to throw an exception if this
FetchPlan setting is set but not serviceable.
>
> One thing that we should test: I'm not convinced that the lock level override in the
DB2Dictionary code is necessary. It's possible that the LockManager will already take into
account the current JDBCFetchConfiguration's lock level settings when specifying the forUpdate
setting for the toSelect() clause. Some test cases will make it easy to figure out the answer
to this question.
>
> > db2 update lock syntax  WITH <isolation> USE AND KEEP UPDATE LOCKS
> > ------------------------------------------------------------------
> >
> >                 Key: OPENJPA-182
> >                 URL: https://issues.apache.org/jira/browse/OPENJPA-182
> >             Project: OpenJPA
> >          Issue Type: New Feature
> >          Components: jdbc
> >         Environment: db2 database driver for zOS, AS400, Unix, Windows, Linux
> >            Reporter: David Wisneski
> >         Assigned To: David Wisneski
> >         Attachments: OPENJPA-182.patch, openJPA182.patch
> >
> >
> > A while back we changed the syntax of update locking from FOR UPDATE OF  to  WITH
RS USE AND KEEP UPDATE LOCKS.   Additional changes are required because
> > 1.  if isolation=serializable is configured, then the syntax should be  WITH RR
USE AND KEEP UDPATE LOCKS
> > 2.  when using DB2/400 on iSeries machines, the syntax is WITH RS USE AND KEEP EXCLUSIVE
LOCKS  or WITH RR USE AND KEEP EXCLUSIVE LOCKS because DB2/400 only supports read or exclusive
locks.
> > 3.  DB2 supports both a FETCH FIRST  ROWS and update LOCKS clauses.
> > So we change supportsLockingWithSelectRange = true in the AbstractDB2Dictionary
class and change the DB2Dictionary to append the correct LOCKS syntax depending on vendor,
release and isolation level.
>
> --
> This message is automatically generated by JIRA.
> -
> You can reply to this email to add a comment to the issue online.
>
>

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