db-derby-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Mike Matrigali (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DERBY-6011) Derby performs very badly (seems to deadlock and timeout) in very simple multi-threaded tests
Date Fri, 11 Jan 2013 19:14:14 GMT

    [ https://issues.apache.org/jira/browse/DERBY-6011?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13551418#comment-13551418
] 

Mike Matrigali commented on DERBY-6011:
---------------------------------------

All the deadlocks I have seen listed are happening on  page 1.  The the dataset particularly
small?  If so I often worry about the optimizer deciding not to use the index in some cases
as it figures out it can get all the rows by just reading a page of the base table.  I think
we have checked query plans, but sometimes they change with execution, especially now with
automatic 
statistics gathering.  It is usually not a problem with real world data sets of more than
a page, but often shows up in test cases where the data set has been made minimal.  

A quick scan of the deadlocks posted seem to all be 2 rows that are one after the other in
the base table.  Need to look at the data set to understand if this relates to the rows being
one after the other in the index (ie. are the rows inserted in index order?).  If so, then
previous key locking is likely involved.  

To debug one could see if the deadlocks still appear if we enable the trace that prints all
query plans to the log on execution.  Or if there are not too many queries could use hints
to force the use of the index 
                
> Derby performs very badly (seems to deadlock and timeout) in very simple multi-threaded
tests
> ---------------------------------------------------------------------------------------------
>
>                 Key: DERBY-6011
>                 URL: https://issues.apache.org/jira/browse/DERBY-6011
>             Project: Derby
>          Issue Type: Bug
>    Affects Versions: 10.7.1.1, 10.8.2.2, 10.9.1.0
>         Environment: Lenovo laptop with SSD's, Windows 7, 64-bit, Sun JDK 1.6.xx
>            Reporter: Karl Wright
>         Attachments: derby.log, manifoldcf.log
>
>
> The Apache ManifoldCF project supports Derby as one of its underlying databases.  Simple
tests, however, demonstrate that Derby is apparently deadlocking and timing out repeatedly
under multi-thread conditions.  This problem is long-standing, and is not exhibited by any
other database ManifoldCF supports, and makes a simple test take between 6x and 12x as long.
> There is a trivial test with demonstrates the problem vs. other databases.  Please do
the following (once you have java 1.6+, svn 1.7+, and ant 1.7+ available):
> (1) Check out https://svn.apache.org/repos/asf/manifoldcf/trunk
> (2) Run the following ant target to download the dependencies: "ant make-core-deps"
> (3) Run the Derby test: "ant run-rss-tests-derby" . Note the time required - at least
180 seconds, can be up to 360 seconds.
> (4) Run the equivalent HSQLDB test: "ant run-rss-tests-HSQLDB".  This test takes about
31 seconds to run.
> The output of the Derby test can be found in the directory "tests/rss/test-derby-output".
 Have a look at manifoldcf.log, where all long-running queries are reported.  Derby.log is
also included, which shows only that during the test's cleanup phase the database is deleted
before it is shutdown, which is not pertinent to the performance issue.
> I am available to assist with ManifoldCF, if that seems to be required.

--
This message is automatically generated by JIRA.
If you think it was sent incorrectly, please contact your JIRA administrators
For more information on JIRA, see: http://www.atlassian.com/software/jira

Mime
View raw message