[jira] Commented: (DERBY-5073) Derby deadlocks without recourse on simultaneous correlated subqueries

["Karl Wright (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/DERBY-5073?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13000605#comment-13000605 ] 

Karl Wright commented on DERBY-5073:
------------------------------------

bq. Note that Derby will only detect a deadlock if the thread holding the exclusive lock is also waiting for a lock itself.

Of course.  I see no reason why that should not be the case here.  There are no threads with a transaction open that are waiting on anything else.


> 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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