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From "Alex (JIRA)" <j...@apache.org>
Subject [jira] [Created] (DERBY-7015) DatabaseMetaData.getTables gives exception when called from two threads and the statement is stale
Date Tue, 30 Oct 2018 18:40:00 GMT
Alex created DERBY-7015:
---------------------------

             Summary: DatabaseMetaData.getTables gives exception when called from two threads
and the statement is stale
                 Key: DERBY-7015
                 URL: https://issues.apache.org/jira/browse/DERBY-7015
             Project: Derby
          Issue Type: Bug
          Components: JDBC
    Affects Versions: 10.14.2.0
         Environment: Linux amd64
            Reporter: Alex
         Attachments: DerbyGetTablesDeadlockTest.java, exception-reported.txt, threads-during-hang.txt

In certain circumstances, when two threads both call DatabaseMetaData.getTables at the same
time, one fails with the exception "A lock could not be obtained within the time requested".

This seems to be when the statement has been executed 100 times (I think as per derby.language.stalePlanCheckInterval)
and the number of rows returned by the query is different compared to the first time getTables
was called.

I attach a test case which reproduces the problem on my workstation most times I execute it.

Output from java org.apache.derby.tools.sysinfo:
{noformat}
------------------ Java Information ------------------
Java Version:    1.8.0_66
Java Vendor:     Oracle Corporation
Java home:       /home/myuser/bin/local/jdk1.8.0_66/jre
Java classpath:  /home/myuser/workspace/DerbyDemo/bin:/home/myuser/workspace/DerbyDemo/lib/derby.jar:/home/myuser/workspace/DerbyDemo/lib/junit-4.11.jar:/home/myuser/workspace/DerbyDemo/lib/hamcrest-core-1.3.jar
OS name:         Linux
OS architecture: amd64
OS version:      4.4.0-134-generic
Java user name:  myuser
Java user home:  /home/myuser
Java user dir:   /home/myuser/workspace/DerbyDemo
java.specification.name: Java Platform API Specification
java.specification.version: 1.8
java.runtime.version: 1.8.0_66-b17
--------- Derby Information --------
[/home/myuser/workspace/DerbyDemo/lib/derby.jar] 10.14.2.0 - (1828579)
------------------------------------------------------
----------------- Locale Information -----------------
------------------------------------------------------
------------------------------------------------------{noformat}
Also attached is the exception that it produces, and also a jstack of the two threads when
everything is hung but before the exception is thrown.

 



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