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MySQL Community Server 5.5.20 has been released
Posted by: hery ramilison
Date: January 11, 2012 11:29AM

Dear MySQL users,

MySQL 5.5.20 is a new version of the 5.5 production release of the
world's most popular open source database. MySQL 5.5.20 is recommended
for use on production systems.

MySQL 5.5 includes several high-impact enhancements to improve the
performance and scalability of the MySQL Database, taking advantage of
the latest multi-CPU and multi-core hardware and operating systems. In
addition, with release 5.5, InnoDB is now the default storage engine for
the MySQL Database, delivering ACID transactions, referential integrity
and crash recovery by default.

MySQL 5.5 also provides a number of additional enhancements including:

    - Significantly improved performance on Windows, with various
      Windows specific features and improvements
    - Higher availability, with new semi-synchronous replication and
      Replication Heart Beat
    - Improved usability, with Improved index and table partitioning,
      SIGNAL/RESIGNAL support and enhanced diagnostics, including a new
      Performance Schema monitoring capability.

For a more complete look at what's new in MySQL 5.5, please see the
following resources:

MySQL 5.5 is GA, Interview with Tomas Ulin:


Whitepaper: What's New in MySQL 5.5:

If you are running a MySQL production level system, we would like to
direct your attention to MySQL Enterprise Edition, which includes the
most comprehensive set of MySQL production, backup, monitoring,
modeling, development, and administration tools so businesses can
achieve the highest levels of MySQL performance, security and uptime.

For information on installing MySQL 5.5.20 on new servers, please see
the MySQL installation documentation at

For upgrading from previous MySQL releases, please see the important
upgrade considerations at:

MySQL Database 5.5.20 is available in source and binary form for a
number of platforms from our download pages at:

Not all mirror sites may be up to date at this point in time, so if you
can't find this version on some mirror, please try again later or choose
another download site.

We welcome and appreciate your feedback, bug reports, bug fixes,
patches, etc.:

The following section lists the changes in the MySQL source code since
the previous released version of MySQL 5.5.  It may also be viewed
online at:


D.1.1. Changes in MySQL 5.5.20 (10 January 2012)

   Functionality Added or Changed

     * A new server option, --slow-start-timeout, controls the
       Windows service control manager's service start timeout. The
       value is the maximum number of milliseconds that the service
       control manager waits before trying to kill the MySQL service
       during startup. The default value is 15000 (15 seconds). If
       the MySQL service takes too long to start, you may need to
       increase this value. A value of 0 means there is no timeout.
       (Bug #45546, Bug #11754011)

   Bugs Fixed

     * Important Change: Replication: Setting an empty user in a
       CHANGE MASTER TO statement caused an invalid internal result
       and is no longer permitted. Trying to use MASTER_USER='' or
       setting MASTER_PASSWORD while leaving MASTER_USER unset causes
       the statement to fail with an error. (Bug #13427949)

     * Important Change: Replication: Moving the binary log file,
       relay log file, or both files to a new location, then
       restarting the server with a new value for --log-bin,
       --relay-log, or both, caused the server to abort on start.
       This was because the entries in the index file overrode the
       new location. In addition, paths were calculated relative to
       datadir (rather than to the --log-bin or --relay-log values).
       The fix for this problem means that, when the server reads an
       entry from the index file, it now checks whether the entry
       contains a relative path. If it does, the relative part of the
       path is replaced with the absolute path set using the
       --log-bin or --relay-log option. An absolute path remains
       unchanged; in such a case, the index must be edited manually
       to enable the new path or paths to be used. (Bug #11745230,
       Bug #12133)

     * InnoDB Storage Engine: When doing a live downgrade from MySQL
       5.6.4 or later, with innodb_page_size
       #sysvar_innodb_page_size) set to a value other than 16384, now
       the earlier MySQL version reports that the page size is
       incompatible with the older version, rather than crashing or
       displaying a "corruption" error. (Bug #13116225)

     * InnoDB Storage Engine: Issuing INSERT...ON DUPLICATE KEY
       statements for InnoDB tables from concurrent threads could
       cause a deadlock
       dlock), particularly with the INSERT...ON DUPLICATE KEY UPDATE
       form. The fix avoids deadlocks caused by the same row being
       accessed by more than one transaction. Deadlocks could still
       occur when multiple rows are inserted and updated
       simultaneously by different transactions in inconsistent
       order; those types of deadlocks require the standard error
       handling on the application side, of re-trying the
       transaction. (Bug #11759688, Bug #52020)

     * An incorrect InnoDB assertion could cause the server to halt.
       This issue only affected debug builds. The assertion
       referenced the source file btr0pcur.ic and the variable
       cursor->pos_state. (Bug #13358468)

     * Locale information for FORMAT() function instances was lost in
       view definitions. (Bug #63020, Bug #13344643)

     * The handle_segfault() signal-handler code in mysqld could
       itself crash due to calling unsafe functions. (Bug #54082, Bug

     * Enabling myisam_use_mmap could cause the server to crash. (Bug
       #48726, Bug #11756764)

     * Concurrent access to ARCHIVE tables could cause corruption.
       (Bug #42784, Bug #11751793)

On behalf of the MySQL Build Team,
Joerg Bruehe/Hery Ramilison

Edited 1 time(s). Last edit at 01/11/2012 11:40AM by hery ramilison.

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MySQL Community Server 5.5.20 has been released
January 11, 2012 11:29AM

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