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From "Karl Wright (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-5073) Derby deadlocks without recourse on simultaneous correlated subqueries
Date Wed, 02 Mar 2011 19:15:36 GMT

    [ https://issues.apache.org/jira/browse/DERBY-5073?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13001558#comment-13001558
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Karl Wright commented on DERBY-5073:
------------------------------------

Is there anything else that would be helpful to diagnose why Derby does not detect a deadlock
here?  I am not certain how to read this output, nor am I sure it will help because it doesn't
tell us what lock the code is TRYING to grab.


> Derby deadlocks without recourse on simultaneous correlated subqueries
> ----------------------------------------------------------------------
>
>                 Key: DERBY-5073
>                 URL: https://issues.apache.org/jira/browse/DERBY-5073
>             Project: Derby
>          Issue Type: Bug
>            Reporter: Karl Wright
>
> When the following two queries are run against tables that contain the necessary fields,
using multiple threads, Derby deadlocks and none of the queries ever returns.  Derby apparently
detects no deadlock condition, either.
> SELECT t0.* FROM jobqueue t0 WHERE EXISTS(SELECT 'x' FROM carrydown t1 WHERE t1.parentidhash
IN (?) AND t1.childidhash=t0.dochash AND t0.jobid=t1.jobid) AND t0.jobid=?
> SELECT t0.* FROM jobqueue t0 WHERE EXISTS(SELECT 'x' FROM carrydown t1 WHERE t1.parentidhash
IN (?) AND t1.childidhash=t0.dochash AND t0.jobid=t1.jobid AND t1.newField=?) AND t0.jobid=?
> This code comes from Apache ManifoldCF, and has occurred when there are five or more
threads trying to execute these two queries at the same time.  Originally we found this on
10.5.3.0.  It was hoped that 10.7.1.1 would fix the problem, but it hasn't.

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