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https://issues.apache.org/jira/browse/OPENJPA-182?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12486819
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Patrick Linskey commented on OPENJPA-182:
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In the hint-based approach, you could set the hints on a particular query.
In my approach, you could configure the FetchPlan for a particular query (get
the Query's fetch plan), or for a particular entity manager (get the EM's fetch
plan). To do different fetch plans for different queries, you'd just set the
different query fetch plans differently.
Query fetch plans are a copy-on-write semantic -- they start off just
delegating through to the EM's fetch plan, and if you make changes, then they
immediately make a copy of the EM's fetch plan, and remain isolated from the
EM's fetch plan from then on out.
If you wanted to do different isolation levels for different find() calls or
different relationship traversals, in my impl, you'd need to set the EM's fetch
plan, do the work, then set it back. In the hint-based impl, you would not be
able to do any configuration for find() or relationship traversals.
> 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.
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