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https://issues.apache.org/jira/browse/OPENJPA-182?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12485103
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Patrick Linskey commented on OPENJPA-182:
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Wow... that's a lot more DB2 locking knowledge than I've ever seen in one
place. Neat.
Some comments on the patch:
1. How does the openjpa.hint.updateClause hint differ from the value of the
forUpdate flag passed in to the DBDictionary call? It looks like the existing
OpenJPA per-transaction read / write lock level configuration could be used
instead.
2. Is openjpa.hint.isolationLevel really a hint, or more of a rule? Again, I
have a hunch that maybe we could do something with the read / write lock
levels, or maybe some other means of controlling isolation level. In any event,
it seems like isolation level isn't really a hint, but rather is more of a rule.
3. You introduced a number of public boolean fields for determining what type
of DB2 instance is being used. Based on code inspection, it looks like you
expect that it should always be possible to automatically determine the type;
maybe these should be private fields instead? We only have public fields in
DBDictionaries for user-configurable settings. Also, since it looks like only
one of the booleans can meaningfully be true, I'd rather see a single private
db2ServerType field that will be set to one of several symbolic constant
values. This will let you replace the if-else block with a switch block if you
prefer that sort of thing, also.
> 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: 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.
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