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MySQL Community Server 5.5.27 has been released
Posted by: hery ramilison
Date: August 03, 2012 12:04PM

Dear MySQL users,

MySQL 5.5.27 is a new version of the 5.5 production release of the
world's most popular open source database. MySQL 5.5.27 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 5.5.27 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 5.5.27 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.

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 5.5.27 (2012-August-02)

Functionality Added or Changed

  * Important Change: The YEAR(2) data type is now deprecated
    because it is problematic. Support for YEAR(2) will be removed
    in a future release of MySQL. For more information, see
    YEAR(2) Limitations and Migrating to YEAR(4)

Bugs Fixed

  * InnoDB: If a row was deleted from an InnoDB table, then
    another row was re-inserted with the same primary key value,
    an attempt by a concurrent transaction to lock the row could
    succeed when it should have waited. This issue occurred if the
    locking select used a WHERE clause that performed an index
    scan using a secondary index. (Bug #14100254, Bug #65389)

  * InnoDB: An assertion could be raised if an InnoDB table was
    moved to a different database using ALTER TABLE ... RENAME
    while the database was being dropped by DROP DATABASE. (Bug

  * InnoDB: Using the KILL statement to terminate a query could
    cause an unnecessary message in the error log:
    [ERROR] Got error -1 when reading table table_name
    (Bug #13933132)

  * InnoDB: For an InnoDB table with a trigger, under the setting
    innodb_autoinc_lock_mode=1, sometimes auto-increment values
    could be interleaved when inserting into the table from two
    sessions concurrently. The sequence of auto-increment values
    could vary depending on timing, leading to data inconsistency
    in systems using replication. (Bug #12752572, Bug #61579)

  * Replication: An event whose length exceeded the size of the
    master dump thread's max_allowed_packet caused replication to
    fail. This could occur when updating many large rows and using
    row-based replication.
    As part of this fix, a new server option
    --slave-max-allowed-packet is added, which permits
    max_allowed_packet to be exceeded by the slave SQL and I/O
    threads. Now the size of a packet transmitted from the master
    to the slave is checked only against this value (available as
    the value of the slave_max_allowed_packet server system
    variable), and not against the value of max_allowed_packet.
    (Bug #12400221, Bug #60926)

  * Replication: Statements such as UPDATE ... WHERE
    primary_key_column = constant LIMIT 1 are flagged as unsafe
    for statement-based logging, despite the fact that such
    statements are actually safe. In cases where a great many such
    statements were run, this could lead to disk space becoming
    exhausted do to the number of such false warnings being
    logged. To prevent this from happening, a warning suppression
    mechanism is introduced. This warning suppression acts as
    follows: Whenever the 50 most recent
    ER_BINLOG_UNSAFE_STATEMENT warnings have been generated more
    than 50 times in any 50-second period, warning suppression is
    enabled. When activated, this causes such warnings not to be
    written to the error log; instead, for each 50 warnings of
    this type, a note is written to the error log stating The last
    warning was repeated N times in last S seconds. This continues
    as long as the 50 most recent such warnings were issued in 50
    seconds or less; once the number of warnings has decreased
    below this threshold, the warnings are once again logged
    The fix for this issue does not affect how these warnings are
    reported to MySQL clients; a warning is still sent to the
    client for each statement that generates the warning. This fix
    also does not make any changes in how the safety of any
    statement for statement-based logging is determined. (Bug
    #11759333, Bug #51638)
    References: See also Bug #11751521, Bug #42415.

  * Replication: After upgrading a replication slave to MySQL
    5.5.18 or later, enabling the query cache eventually caused
    the slave to fail. (Bug #64624, Bug #14005409)

  * The server did not build with gcc 4.7. (Bug #14238406)

  * Certain arguments to RPAD() could lead to "uninitialized
    variable" warnings. (Bug #14039955)

  * The presence of a file named .empty in the test database
    prevented that database from being dropped. (Bug #12845091)

  * For some subqueries that should be executed using a range scan
    on a non-primary index and required use of filesort, only the
    first execution of the subquery was done as a range scan. All
    following executions were done as full table scans, resulting
    in poor performance. (Bug #12667154)

  * File access by the ARCHIVE storage engine was not instrumented
    and thus not shown in Performance Schema tables. (Bug #63340,
    Bug #13417440)

  * mysqlbinlog exited with no error code if file write errors
    occurred. (Bug #55289, Bug #11762667)

  * Using CONCAT() to construct a pattern for a LIKE pattern match
    could result in memory corrupting and match failure. (Bug
    #59140, Bug #11766101)

  * yaSSL rejected valid SSL certificates that OpenSSL accepts.
    (Bug #54348, Bug #11761822)

  * Sessions could end up deadlocked when executing a combination
    (Bug #60682, Bug #12636001)

  * mysqldump could dump views and the tables on which they depend
    in such an order that errors occurred when the dump file was
    reloaded. (Bug #44939, Bug #11753490)

On behalf of the MySQL/ORACLE Build Team

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Written By
MySQL Community Server 5.5.27 has been released
August 03, 2012 12:04PM

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