db-derby-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Kristian Waagan (JIRA)" <j...@apache.org>
Subject [jira] Created: (DERBY-4881) Deadlock accessing SYS.SYSSTATISTICS
Date Tue, 02 Nov 2010 11:44:24 GMT
Deadlock accessing SYS.SYSSTATISTICS

                 Key: DERBY-4881
                 URL: https://issues.apache.org/jira/browse/DERBY-4881
             Project: Derby
          Issue Type: Bug
          Components: SQL
    Affects Versions:,,,,
            Reporter: Kristian Waagan
            Assignee: Kristian Waagan
            Priority: Minor

Transactions accessing index statistics can deadlock if one of them inserts new entries and
the other selects from the system table. Inserts happens for instance when update of index
statistics are perform manually, or when a table is compressed (given that the table has indexes
and contains some rows). This issue may be more problematic when automatic update of index
statistics is implemented.
Issue discovered when writing a regression tests for DERBY-4849, see discussion there. The
bug is timing dependent, but has been observed on a variety of JVMs and platform architectures.

To sum up:
  o using NO_WAIT + retry was suggested, but turned out to be an infeasible solution
  o current approach is to allow using read uncommitted isolation level when accessing statistics
in the system table (take no locks)

This message is automatically generated by JIRA.
You can reply to this email to add a comment to the issue online.

View raw message