Dear MySQL users,
MySQL 5.5.25a is a new version of the 5.5 production release of the
world's most popular open source database. MySQL 5.5.25a is recommended
for use on production systems.
MySQL 5.5.25a is a replacement of MySQL 5.5.25, in that version a
regression bug was detected in the optimizer (Bug #65745).
Because of this, MySQL 5.5.25 has been removed from the download sites.
We recommend that users who have installed MySQL 5.5.25 upgrade to
MySQL 5.5.25a at the earliest opportunity.
That bug is specific to MySQL 5.5.25, other versions are not affected.
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
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 5.5.25a 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 5.5.25a 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,
The following sections list the changes in the MySQL source code since
the previous released versions, MySQL 5.5.25 (withdrawn) and MySQL
5.5.24. They may also be viewed online at:
D.1.2. Changes in MySQL 5.5.25a (2012-July-05)
Due to MSI restrictions, the MSI packages of MySQL 5.5.25a will
treat the version as 5.5.26 internally; for example, as displayed
by the Installation Wizard. MySQL itself reports the version as
5.5.25a; for example, if you check the value of the VERSION() SQL
function or the version system variable.
* A regression bug in the optimizer could cause excessive disk
usage for UPDATE statements. (Bug #65745, Bug #14248833)
D.1.3. Changes in MySQL 5.5.25 (2012-May-30)
MySQL 5.5.25 is superseded by MySQL 5.5.25a due to a regression bug
that can cause excessive disk usage (for details, see Bug #65745).
Current users of 5.5.25: Monitor disk usage and upgrade to 5.5.25a
as soon as that is made available.
Users contemplating upgrades to 5.5.25: Defer and upgrade to 5.5.25a
instead when that is made available.
Functionality Added or Changed
* Important Change: Replication: The SHOW BINARY LOGS statement
(and its equivalent SHOW MASTER LOGS) may now be executed by a
user with the REPLICATION CLIENT privilege. (Formerly, the
SUPER privilege was necessary to use either form of this
* The --safe-mode server option now is deprecated and will be
removed in MySQL 5.6.
* Performance: InnoDB: Improved the algorithm related to
adaptive flushing. This fix increases the rate of flushing in
cases where compression is used and the data set is larger
than the buffer pool, leading to eviction. (Bug #13990648, Bug
* InnoDB: In a transaction using the REPEATABLE READ isolation
level, an UPDATE or DELETE statement for an InnoDB table could
sometimes overlook rows recently committed by other
transactions. As explained in Section 126.96.36.199, "Consistent
Nonlocking Reads," DML statements within a REPEATABLE READ
transaction apply to rows committed by other transactions,
even if a query could not see those rows. (Bug #14007649, Bug
* InnoDB: The Innodb_buffer_pool_pages_flushed status variable
was incorrectly set to twice the value it should be. Its value
should never exceed the value of Innodb_pages_written. (Bug
#14000361, Bug #65030)
* InnoDB: The error handling and message was improved for
attempting to create a foreign key with a column referencing
itself. The message suggested a potential problem with the
data dictionary, when no such problem existed. (Bug #12902967)
* InnoDB: The CHECK TABLE statement could fail for a large
InnoDB table due to a timeout value of 2 hours. For typical
storage devices, the issue could occur for tables that
exceeded approximately 200 or 350 GB, depending on I/O speed.
The fix relaxes the locking performed on the table being
checked, which makes the timeout less likely. It also makes
InnoDB recognize the syntax CHECK TABLE QUICK, which avoids
the possibility of the timeout entirely. (Bug #11758510, Bug
* Replication: It was theoretically possible for concurrent
execution of more than one instance of SHOW BINLOG EVENTS to
crash the MySQL Server. (Bug #13979418)
* Replication: Statements using AUTO_INCREMENT,
LAST_INSERT_ID(), RAND(), or user variables could be applied
in the wrong context on the slave when using statement-based
replication and replication filtering server options (see
Section 16.2.3, "How Servers Evaluate Replication Filtering
Rules"). (Bug #11761686, Bug #54201)
References: See also Bug #11754117, Bug #45670, Bug #11746146,
* Replication: An INSERT into a table that has a composite
primary key that includes an AUTO_INCREMENT column that is not
the first column of this composite key is not safe for
statement-based binary logging or replication. Such statements
are now marked as unsafe and fail with an error when using the
STATEMENT binary logging format. For more information, see
Section 188.8.131.52, "Determination of Safe and Unsafe Statements
in Binary Logging," as well as Section 184.108.40.206, "Replication
Tables using the InnoDB storage engine are not affected by
this issue, since InnoDB does not allow the creation of a
composite key that includes an AUTO_INCREMENT column, where
this column is not the first column in the key.
(Bug #11754117, Bug #45670)
References: See also Bug #11761686, Bug #54201, Bug #11746146,
* SHOW TABLES was very slow unless the required information was
already in the disk cache. (Bug #60961, Bug #12427262)
On behalf of the MySQL Build Team,
|• MySQL Community Server 5.5.25a has been released||karen langford||5 Jul|