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From "Patrick Linskey" <plins...@bea.com>
Subject RE: [jira] Commented: (OPENJPA-182) db2 update lock syntax WITH <isolation> USE AND KEEP UPDATE LOCKS
Date Thu, 05 Apr 2007 22:56:20 GMT
> 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.

I just did this in r525997. I also added a couple of test cases.
TestSelectForUpdateOverride asserts that the DBDictionary is called with
the appropriate forUpdate setting based on fetch configuration and
transaction data; TestIsolationLevelOverride tests the behavior of the
new JDBCFetchPlan.setIsolationLevel() API.

I committed this on the assumption that Abe will agree that since a
number of databases support this concept, it makes sense to have a
common API for it.

-Patrick

-- 
Patrick Linskey
BEA Systems, Inc. 

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> -----Original Message-----
> From: David Wisneski [mailto:wisneskid@gmail.com] 
> Sent: Thursday, April 05, 2007 11:35 AM
> To: open-jpa-dev@incubator.apache.org
> Subject: Re: [jira] Commented: (OPENJPA-182) db2 update lock 
> syntax WITH <isolation> USE AND KEEP UPDATE LOCKS
> 
> 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.atl
assian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_1248704
6 ]
> >
> > 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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