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From "Myrna van Lunteren (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DERBY-5448) In the 10.8 branch, back out the concurrency improvements introduced by using SequenceUpdaters to allocate identity values.
Date Thu, 06 Oct 2011 19:23:29 GMT

    [ https://issues.apache.org/jira/browse/DERBY-5448?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13122182#comment-13122182
] 

Myrna van Lunteren commented on DERBY-5448:
-------------------------------------------

One more thing I thought to mention: I've not seen deadlocks in this test since I started
running them (for QA cycle for 10.5, I think), but comments in the test lead me to believe
they may have been possible.
I'm referring to this section in the Tester1 class:
		// Too many deadlocks amd locking issues if this is not commented out
		try {
			connex.setAutoCommit(false);
		} catch (Exception e) {
			System.out.println("FAIL: " + getThread_id()
					+ "'s setAutoCommit() failed:");
			printException("setting AutoCommit", e);
		}

		// also set isolation level to Connection.TRANSACTION_READ_UNCOMMITTED
		// to reduce number of
		// deadlocks
		setIsolationLevel(Connection.TRANSACTION_READ_UNCOMMITTED);
So perhaps a different hardware/jvm combination is more/less likely to run into deadlock situations...?

                
> In the 10.8 branch, back out the concurrency improvements introduced by using SequenceUpdaters
to allocate identity values.
> ---------------------------------------------------------------------------------------------------------------------------
>
>                 Key: DERBY-5448
>                 URL: https://issues.apache.org/jira/browse/DERBY-5448
>             Project: Derby
>          Issue Type: Bug
>          Components: Documentation, SQL
>    Affects Versions: 10.8.2.1
>            Reporter: Rick Hillegas
>             Fix For: 10.8.2.1
>
>         Attachments: derby-5448-01-aa-backoutConcurrencyChanges.diff, derby-5448-02-aa-backoutDocsChanges.diff
>
>
> New errors were seen while running NsTest against the 10.8.2 release candidates. These
errors are recorded as DERBY-5430 and DERBY-5422. The first error is a deadlock which occurs
when inserting into the main table of the test. The second error is a problem clearing the
identity cache. These errors have caused people to lose confidence in the concurrency improvements
introduced by DERBY-4437. We should back the DERBY-4437 changes out of the 10.8 branch and
use the trunk to continue debugging the problems disclosed by NsTest.

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