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MySQL Community Server 5.5.23 has been released
Posted by: hery ramilison
Date: April 13, 2012 10:22AM

Dear MySQL users,

MySQL 5.5.23 is a new version of the 5.5 production release of the
world's most popular open source database. MySQL 5.5.23 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 5.5.23 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 5.5.23 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:


Changes in MySQL 5.5.23 (12 April 2012)

Functionality Added or Changed

* The MySQL-shared-compat RPM package enables users of Red
Hat-privided mysql-*-5.1 RPM packages to migrate to
Oracle-provided MySQL-*-5.5 packages. MySQL-shared-compat now
replaces the Red Hat mysql-libs package by replacing files of the latter package, thus satisfying
dependencies of other packages on mysql-libs. This change
affects only users of Red Hat (or Red Hat-compatible) RPM
packages. Nothing is different for users of Oracle RPM
packages. (Bug #13867506)

Bugs Fixed

* Security Fix: Bug #59533 was fixed.

* Performance: Partitioning: InnoDB Storage Engine: The
statistics used by the optimizer for queries against
partitioned InnoDB tables were based only on the first
partition of each such table, leading to use of the wrong
execution plan. (Bug #13694811)
References: This bug was introduced by Bug #11756867.

* Performance: InnoDB Storage Engine: Improved the performance
of the DROP TABLE statement for InnoDB tables, especially on
systems with a large buffer pool. The fix speeds up the
processing for freeing entries in the adaptive hash index.
(Bug #13704145, Bug #64284)

* InnoDB Storage Engine: Deleting a huge amount of data from
InnoDB tables within a short time could cause the purge
operation that flushes data from the buffer pool to stall. If
this issue occurs, restart the server to work around it. This
issue is only likely to occur on 32-bit platforms. (Bug

* InnoDB Storage Engine: If the server crashed during a TRUNCATE
TABLE or CREATE INDEX statement for an InnoDB table, or a DROP
DATABASE statement for a database containing InnoDB tables, an
index could be corrupted, causing an error message when
accessing the table after restart:
InnoDB: Error: trying to load index index_name for table
InnoDB: table_name but the index tree has been freed!
In MySQL 5.1, this fix applies to the InnoDB Plugin, but not
the built-in InnoDB storage engine. (Bug #12861864, Bug

* InnoDB Storage Engine: When data was removed from an InnoDB
table, newly inserted data might not reuse the freed disk
blocks, leading to an unexpected size increase for the system
tablespace or .ibd file (depending on the setting of
innodb_file_per_table. The OPTIMIZE TABLE could compact a .ibd
file in some cases but not others. The freed disk blocks would
eventually be reused as additional data was inserted. (Bug
#11766634, Bug #59783)

* Partitioning: After updating a row of a partitioned table and
selecting that row within the same transaction with the query
cache enabled, then performing a ROLLBACK, the same result was
returned by an identical SELECT issued in a new transaction.
(Bug #11761296, Bug #53775)

* Replication: Formerly, the default value shown for the Port
column in the output of SHOW SLAVE HOSTS was 3306 whether the
port had been set incorrectly or not set at all. Now, when the
slave port is not set, 0 is used as the default. This change
also affects the default used for the --report-port server
option. (Bug #13333431)

* Replication: The --relay-log-space-limit option was sometimes
More specifically, when the SQL thread went to sleep, it
allowed the I/O thread to queue additional events in such a
way that the relay log space limit was bypassed, and the
number of events in the queue could grow well past the point
where the relay logs needed to be rotated. Now in such cases,
the SQL thread checks to see whether the I/O thread should
rotate and provide the SQL thread a chance to purge the logs
(thus freeing space).
Note that, when the SQL thread is in the middle of a
transaction, it cannot purge the logs; it can only ask for
more events until the transaction is complete. Once the
transaction is finished, the SQL thread can immediately
instruct the I/O thread to rotate. (Bug #12400313, Bug #64503)
References: See also Bug #13806492.

* An infinite thread loop could develop within Performance
Schema, causing the server to become unresponsive. (Bug

* Incorrect stored program caching could cause statements within
a stored program that included a GROUP BY clause to return
different results across multiple program invocations. (Bug

* Mishandling of NO_BACKSLASH_ESCAPES SQL mode within stored
procedures on slave servers could cause replication failures.
(Bug #12601974)

* SAVEPOINT statements were incorrectly disallowed within XA
transactions. (Bug #64374, Bug #13737343)
References: See also Bug #11766752.

* The Performance Schema incorrectly displayed some backslashes
in Windows file names (by doubling them). (Bug #63339, Bug

* SHOW statements treated stored procedure, stored function, and
event names as case sensitive. (Bug #56224, Bug #11763507)

On behalf of the MySQL Build Team,

Hery Ramilison
MySQL/ORACLE Release Engineering Team

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Written By
MySQL Community Server 5.5.23 has been released
April 13, 2012 10:22AM

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