Dear MySQL users,
MySQL Server 5.5.7-rc, a new version of the popular Open Source
Database Management System, has been released.
The "-rc" suffix indicates this is a "release candidate". When there is
sufficient positive feedback, there will be a "GA" (production quality)
version of 5.5. From then on, MySQL 5.5 will receive production bug
For commercial offerings, see
MySQL 5.5 includes several high-impact changes to address scalability
and performance issues in MySQL Server. These changes exploit advances
in hardware and CPU design and enable better utilization of existing
For an overview of what's new in MySQL 5.5, please see the section
"What Is New in MySQL 5.5" online at
The new features in these releases are above beta quality. As with any
other pre-production release, caution should be taken when installing
on production level systems or systems with critical data.
For information on installing MySQL 5.5.7-rc on new servers, please see
the MySQL installation documentation at
For upgrading from previous MySQL releases, please see the important
upgrade considerations at
MySQL Server 5.5 is available in source and binary form for a number of
platforms from the "Development Releases" selection of 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 complete list of all "Bugs Fixed" may be viewed online at
Special note for those of you who build from source:
Since MySQL 5.5.5-m3, CMake has been used as the build framework for all
platforms. See how you can use CMake as per the instructions on this web
The official packages for this release have been produced using CMake.
As always, we value your feedback!
Changes in MySQL 5.5.7-rc:
* MySQL authentication supports two new capabilities, pluggable
authentication and proxy users:
+ With pluggable authentication, the server can use plugins
to authenticate incoming client connections, and clients
can load an authentication plugin that interacts properly
with the corresponding server plugin. This capability
enables clients to connect to the MySQL server with
credentials that are appropriate for authentication
methods other than the built-in MySQL authentication
based on native MySQL passwords stored in the mysql.user
table. For example, plugins can be created to use
external authentication methods such as LDAP, Kerberos,
PAM, or Windows login IDs.
+ Proxy user capability enables a client who connects and
authenticates as one user to be treated, for purposes of
access control while connected, as having the privileges
of a different user. In effect, one user impersonates
another. Proxy capability depends on pluggable
authentication because it is based on having an
authentication plugin return to the server the user name
that the connecting user impersonates.
Pluggable authentication entails these changes:
+ For user specifications in the CREATE USER and GRANT
statements, a new IDENTIFIED WITH clause for specifying
the authentication plugin.
+ For the mysql.user table, new columns that specify plugin
information. The plugin column, if nonempty, indicates
which plugin authenticates connections for an account.
The authentication_string column is a string that is
passed to the plugin.
+ For the mysql_options() C API function, new
MYSQL_DEFAULT_AUTH and MYSQL_PLUGIN_DIR options that
enable client programs to load authentication plugins.
+ For the mysql client, new --default-auth and --plugin-dir
options for specifying which authentication plugin and
plugin directory to use.
+ For the mysqltest client, a new --plugin-dir option for
specifying which plugin directory to use, and a new
connect() command argument to specify an authentication
+ For the server plugin API, a new
MYSQL_AUTHENTICATION_PLUGIN plugin type.
+ A client plugin API that enables client programs to
+ Reimplementation of the built-in authentication methods
previously supported in MySQL as plugins. These methods
provide native password checking and pre-MySQL 4.1.1
authentication that uses shorter password hash values.
This change only reimplements the built-in methods as
plugins that cannot be unloaded. Existing clients
authenticate as before with no changes needed. In
particular, starting the server with the --secure-auth
option still prevents clients that have pre-4.1.1
password hashes from connecting, and --skip-grant-tables
still disables all password checking.
Proxy user capability entails these changes:
+ A new PROXY privilege that can be managed with the GRANT
and REVOKE statements.
+ New proxy_user and external_user system variables that
indicate whether the current session uses proxying.
+ A new mysql.proxies_priv grant table that records proxy
information for MySQL accounts.
Due to these changes, the server requires that the new grant
table, proxies_priv, be present in the mysql database. If you
are upgrading from a previous MySQL release rather than
performing a new installation, the server will exit during
startup after finding that this table is missing. To create
the table, start the server with the --skip-grant-tables
option to cause it to skip the normal grant table checks, then
run mysql_upgrade. For example:
shell> mysqld --skip-grant-tables &
Then stop the server and restart it normally.
You can specify other options on the mysqld command line if
necessary. Alternatively, if your installation is configured
so that the server normally reads options from an option file,
use the --defaults-file option to specify the file (enter each
command on a single line):
shell> mysqld --defaults-file=/usr/local/mysql/etc/my.cnf
With the --skip-grant-tables option, the server does no
password or privilege checking, so any client can connect and
effectively have all privileges. For additional security, use
the --skip-networking option as well to prevent remote clients
For additional information, consult these references:
+ Information about pluggable authentication, including
installation and usage instructions: Section 5.5.6,
+ Information about proxy users: Section 5.5.7, "Proxy
+ Information about the server and client plugin API:
Section 184.108.40.206, "General Plugin Data Structures and
+ Information about the C API functions for managing client
plugins: See Section 22.9.10, "Client Plugin API C
Functionality added or changed:
* The unused and undocumented thread_pool_size system variable
* A new status variable, Handler_read_last, displays the number
of requests to read the last key in an index. With ORDER BY,
the server will issue a first-key request followed by several
next-key requests, whereas with With ORDER BY DESC, the server
will issue a last-key request followed by several previous-key
requests. (Bug#52312: http://bugs.mysql.com/bug.php?id=52312)
* Performance: InnoDB Storage Engine: The master InnoDB
background thread could sometimes cause transient performance
drops due to excessive flushing of modified pages.
* Security Fix: The server crashed for assignment of values of
types other than Geometry to items of type GeometryCollection
(MultiPoint, MultiCurve, MultiSurface). Now the server checks
the field type and fails with bad geometry value if it detects
* Security Fix: EXPLAIN EXTENDED caused a server crash with some
* Security Fix: In prepared-statement mode, EXPLAIN for a SELECT
from a derived table caused a server crash.
* Security Fix: The PolyFromWKB() function could crash the
server when improper WKB data was passed to the function.
* Incompatible Change: Replication: The behavior of INSERT
DELAYED statements when using statement-based replication has
changed as follows:
Previously, when using binlog_format=STATEMENT, a warning was
issued in the client when executing INSERT DELAYED; now, no
warning is issued in such cases.
Previously, when using binlog_format=STATEMENT, INSERT DELAYED
was logged as INSERT DELAYED; now, it is logged as an INSERT,
without the DELAYED option.
However, when binlog_format=STATEMENT, INSERT DELAYED
continues to be executed as INSERT (without the DELAYED
option). The behavior of INSERT DELAYED remains unchanged when
using binlog_format=ROW: INSERT DELAYED generates no warnings,
is executed as INSERT DELAYED, and is logged using the
This change also affects binlog_format=MIXED, because INSERT
DELAYED is no longer considered unsafe. Now, when the logging
format is MIXED, no switch to row-based logging occurs. This
means that the statement is logged as a simple INSERT (that
is, without the DELAYED option), using the statement-based
* Incompatible Change: Previously, if you flushed the logs using
FLUSH LOGS or mysqladmin flush-logs and mysqld was writing the
error log to a file (for example, if it was started with the
--log-error option), it renamed the current log file with the
suffix -old, then created a new empty log file. This had the
problem that a second log-flushing operation thus caused the
original error log file to be lost unless you saved it under a
different name. For example, you could use the following
commands to save the file:
shell> mysqladmin flush-logs
shell> mv host_name.err-old backup-directory
To avoid the preceding file-loss problem, renaming no longer
occurs. The server merely closes and reopens the log file. To
rename the file, you can do so manually before flushing. Then
flushing the logs reopens a new file with the original file
name. For example, you can rename the file and create a new
one using the following commands:
shell> mv host_name.err host_name.err-old
shell> mysqladmin flush-logs
shell> mv host_name.err-old backup-directory
* InnoDB Storage Engine: Replication: If the master had
innodb_file_per_table=OFF, innodb_file_format=Antelope (and
innodb_strict_mode=OFF), or both, certain CREATE TABLE
options, such as KEY_BLOCK_SIZE, were ignored. This could
allow master to avoid raising ER_TOO_BIG_ROWSIZE errors.
However, the ignored CREATE TABLE options were still written
into the binary log, so that, if the slave had
innodb_file_per_table=ON and innodb_file_format=Barracuda, it
could encounter an ER_TOO_BIG_ROWSIZE error while executing
the record from the log, causing the slave SQL thread to abort
and replication to fail.
In the case where the master was running MySQL 5.1 and the
slave was MySQL 5.5 (or later), the failure occurred when both
master and slave were running with default values for
innodb_file_per_table and innodb_file_format. This could cause
problems during upgrades.
To address this issue, the default values for
innodb_file_per_table and innodb_file_format are reverted to
the MySQL 5.1 default values---that is, OFF and Antelope,
* InnoDB Storage Engine: The server could crash with a high
volume of concurrent LOCK TABLE and UNLOCK TABLES statements.
* InnoDB Storage Engine: InnoDB incorrectly reported an error
when a cascading foreign key constraint deleted more than 250
rows. (Bug#57255: http://bugs.mysql.com/bug.php?id=57255)
* InnoDB Storage Engine: The output from the SHOW ENGINE INNODB
STATUS command can now be up to 1 MB. Formerly, it was
truncated at 64 KB. Monitoring applications that parse can
check if output exceeds this new, larger limit by testing the
Innodb_truncated_status_writes status variable.
* InnoDB Storage Engine: A SELECT ... FOR UPDATE statement
affecting a range of rows in an InnoDB table could cause a
crash in the debug version of the server.
* InnoDB Storage Engine: Improved the performance of UPDATE
operations on InnoDB tables, when only non-indexed columns are
changed. (Bug#56340: http://bugs.mysql.com/bug.php?id=56340)
* InnoDB Storage Engine: When MySQL was restarted after a crash
with the option innodb_force_recovery=6, certain queries
against InnoDB tables could fail, depending on WHERE or ORDER
Usually in such a disaster recovery situation, you dump the
entire table using a query without these clauses. During
advanced troubleshooting, you might use queries with these
clauses to diagnose the position of the corrupted data, or to
recover data following the corrupted part.
* InnoDB Storage Engine: The CHECK TABLE command could cause a
time-consuming verification of the InnoDB adaptive hash index
memory structure. Now this extra checking is only performed in
binaries built for debugging.
* InnoDB Storage Engine: A heavy workload with a large number of
threads could cause a crash in the debug version of the
server. (Bug#55699: http://bugs.mysql.com/bug.php?id=55699)
* InnoDB Storage Engine: The server could crash on shutdown, if
started with --innodb-use-system-malloc=0.
* InnoDB Storage Engine: If the server crashed during a RENAME
TABLE operation on an InnoDB table, subsequent crash recovery
could fail. This problem could also affect an ALTER TABLE
statement that caused a rename operation internally.
* InnoDB Storage Engine: Setting the PACK_KEYS=0 table option
for an InnoDB table prevented new indexes from being added to
the table. (Bug#54606: http://bugs.mysql.com/bug.php?id=54606)
* InnoDB Storage Engine: Changed the locking mechanism for the
InnoDB data dictionary during ROLLBACK operations, to improve
concurrency for REPLACE statements.
* InnoDB Storage Engine: With multiple buffer pools enabled,
InnoDB could flush more data from the buffer pool than
necessary, causing extra I/O overhead.
* InnoDB Storage Engine: InnoDB transactions could be
incorrectly committed during recovery, rather than rolled
back, if the server crashed and was restarted after performing
ALTER TABLE...ADD PRIMARY KEY on an InnoDB table, or some
other operation that involves copying the entire table.
* InnoDB Storage Engine: InnoDB startup messages now include the
start and end times for buffer pool initialization, and the
total buffer pool size.
* Partitioning: Multi-table UPDATE statements involving a
partitioned MyISAM table could cause this table to become
corrupted. Not all tables affected by the UPDATE needed to be
partitioned for this issue to be observed.
* Partitioning: EXPLAIN PARTITIONS returned bad estimates for
range queries on partitioned MyISAM tables. In addition,
values in the rows column of EXPLAIN PARTITIONS output did not
take partition pruning into account.
* Replication: SET PASSWORD caused row-based replication to fail
between a MySQL 5.1 master and a MySQL 5.5 slave.
This fix makes it possible to replicate SET PASSWORD
correctly, using row-based replication between a master
running MySQL 5.1.53 or a later MySQL 5.1 release to a slave
running MySQL 5.5.7 or a later MySQL 5.5 release.
See also Bug#55452: http://bugs.mysql.com/bug.php?id=55452,
* Replication: Backticks used to enclose identifiers for
savepoints were not preserved in the binary log, which could
lead to replication failure when the identifier, stripped of
backticks, could be misinterpreted, causing a syntax or other
This could cause problems with MySQL application programs
making use of generated savepoint IDs. If, for instance,
java.sql.Connection.setSavepoint() is called without any
parameters, Connector/J automatically generates a savepoint
identifier consisting of a string of hexadecimal digits 0-F
encased in backtick (`) characters. If such an ID took the
form `NeN` (where N represents a string of the decimal digits
0-9, and e is a literal uppercase or lowercase "E" character).
Removing the backticks when writing the identifier into the
binary log left behind a substring which the slave MySQL
server tried to interpret as a floating point number, rather
than as an identifier. The resulting syntax error caused loss
See also Bug#55962: http://bugs.mysql.com/bug.php?id=55962.
* Replication: When a slave tried to execute a transaction
larger than the slave's value for max_binlog_cache_size, it
crashed. This was caused by an assertion that the server
should roll back only the statement but not the entire
transaction when the error ER_TRANS_CACHE_FULL occurred.
However, the slave SQL thread always rolled back the entire
transaction whenever any error occurred, regardless of the
type of error.
* Replication: The error message for
ER_SLAVE_HEARTBEAT_VALUE_OUT_OF_RANGE was hard coded in
English in sql_yacc.yy, so that it could not be translated in
errmsg.txt for other languages.
Additionally, this same error message was used for three
separate error conditions:
1. When the heartbeat period exceeded the value of
2. When the heartbeat period was nonnegative but shorter
than 1 millisecond.
3. When the value for the heartbeat period was either
negative or greater than the maximum allowed.
These issues have been addressed as follows:
+ By using three distinct error messages for each of the
conditions listed previously.
+ By moving the sources for these error messages into the
errmsg-utf8.txt file to facilitate translations into
languages other than English.
* A buffer overrun could occur when formatting DBL_MAX numbers.
* The server could crash inside memcpy() when reading certain
Performance Schema tables.
* Memory leaks detected by Valgrind were corrected.
* It was possible to compile mysqld with Performance Schema
support but with a dummy atomic-operations implementation,
which caused a server crash. This problem does not affect
binary distributions. It is helpful as a safety measure for
users who build MySQL from source.
* The server crashed if a table maintenance statement such as
ANALYZE TABLE or REPAIR TABLE was executed on a MERGE table
and opening and locking a child table failed. For example,
this could happen if a child table did not exist or if a lock
timeout happened while waiting for a conflicting metadata lock
As a consequence of this bug fix, it is now possible to use
CHECK TABLE for log tables without producing an error.
* Deadlock could occur for heavily concurrent workloads
consisting of a mix of DML, DDL, and FLUSH TABLES statements
affecting the same set of tables.
* The server could crash during shutdown due to a race condition
relating to Performance Schema cleanup.
* ALTER TABLE on a MERGE table could result in deadlock with
* The tcmalloc library was missing from binary MySQL packages
for Linux. (Bug#56267: http://bugs.mysql.com/bug.php?id=56267)
* An INSERT DELAYED statement for a MERGE table could cause
deadlock if it occurred as part of a transaction or under LOCK
TABLES, and there was a concurrent DDL or LOCK TABLES ...
WRITE statement that tried to lock one of its underlying
tables. (Bug#56251: http://bugs.mysql.com/bug.php?id=56251)
* In debug builds, the server raised an assertion for DROP
DATABASE in installations that had an outdated or corrupted
mysql.proc table. For example, this affected mysql_upgrade
when run as part of a MySQL 5.1 to 5.5 upgrade.
* A negative TIME argument to MIN() or MAX() could raise an
assertion. (Bug#56120: http://bugs.mysql.com/bug.php?id=56120)
* The ordering for supplementary characters with the
utf8mb4_bin, utf16_bin, and utf32_bin collations was
incorrect. (Bug#55980: http://bugs.mysql.com/bug.php?id=55980)
* Short (single-letter) command-line options did not work.
* If a query specified a DATE or DATETIME value in a format
different from 'YYYY-MM-DD HH:MM:SS', a greater-than-or-equal
(>=) condition matched only greater-than values in an indexed
* If a view was named as the destination table for CREATE TABLE
... SELECT, the server produced a warning whether or not IF
NOT EXISTS was used. Now it produces a warning only when IF
NOT EXISTS is used, and an error otherwise.
* After the fix for
Bug#39653: http://bugs.mysql.com/bug.php?id=39653, the
shortest available secondary index was used for full table
scans. The primary clustered key was used only if no secondary
index could be used. However, when the chosen secondary index
includes all columns of the table being scanned, it is better
to use the primary index because the amount of data to scan is
the same but the primary index is clustered. This is now taken
* For Performance Schema, the default number of rwlock classes
was increased to 30, and the default number of rwlock and
mutex instances was increased to 1 million. These changes were
made to account for the volume of data instrumented when the
InnoDB storage engine is used (because of the InnoDB buffer
pool). (Bug#55576: http://bugs.mysql.com/bug.php?id=55576)
* If there was an active SELECT statement, an error arising
during trigger execution could cause a server crash.
* Assignment of InnoDB scalar subquery results to a variable
resulted in unexpected S locks in READ COMMITTED transaction
* Queries involving predicates of the form const NOT BETWEEN
not_indexed_column AND indexed_column could return incorrect
data due to incorrect handling by the range optimizer.
* With an UPDATE IGNORE statement including a subquery that was
evaluated using a temporary table, an error transferring the
data from the temporary was ignored, causing an assertion to
be raised. (Bug#54543: http://bugs.mysql.com/bug.php?id=54543)
* MIN() or MAX() with a subquery argument could raise a debug
assertion for debug builds or return incorrect data for
* If one session attempted to drop a database containing a table
which another session had opened with HANDLER, any instance of
ALTER DATABASE, CREATE DATABASE, or DROP DATABASE issued by
the latter session produced a deadlock.
* INFORMATION_SCHEMA plugins with no deinit() method resulted in
a memory leak.
* Row subqueries producing no rows were not handled as UNKNOWN
values in row comparison expressions.
* Setting SETUP_INSTRUMENTS.TIMER = 'NO' caused TIMER_WAIT
values for aggregations to be NULL rather than 0.
* The max_length metadata value of MEDIUMBLOB types was reported
as 1 byte greater than the correct value.
* If an application using the embedded server called
mysql_library_init() a second time after calling
mysql_library_init() and mysql_library_end() to start and stop
the server, the application crashed when reading option files.
* The fix for Bug#30234: http://bugs.mysql.com/bug.php?id=30234
caused the server to reject the DELETE tbl_name.* ... Access
compatibility syntax for multiple-table DELETE statements.
* The plugin_ftparser.h and plugin_audit.h include files are
part of the public API/ABI, but were not tested by the ABI
check. (Bug#52821: http://bugs.mysql.com/bug.php?id=52821)
* An atomic "compare and swap" operation using x86 assembly code
(32 bit) could access incorrect data, which would make it work
incorrectly and lose the intended atomicity. This would in
turn cause the MySQL server to work on inconsistent data
structures and return incorrect data. That code part affected
only 32-bit builds; the effect has been observed when icc was
used to build binaries. With gcc, no incorrect results have
been observed during tests, so this fix is a proactive one.
Other compilers do not use this assembly code.
* In LOAD DATA INFILE, using a SET clause to set a column equal
to itself caused a server crash.
* In some cases, when the left part of a NOT IN subquery
predicate was a row and contained NULL values, the query
result was incorrect.
* CHECKSUM TABLE for Performance Schema tables could cause a
server crash due to uninitialized memory reads.
* For some queries, the optimizer produced incorrect results
using the Index Merge access method with InnoDB tables.
* EXPLAIN produced an incorrect rows value for queries evaluated
using an index scan and that included LIMIT, GROUP BY, and
ORDER BY on a computed column.
* mysql_store_result() and mysql_use_result() are not for use
with prepared statements and are not intended to be called
following mysql_stmt_execute(), but failed to return an error
when invoked that way.
* Using REPAIR TABLE table USE_FRM on a MERGE table caused the
server to crash.
* If the global and session debug system variables had the same
value, the debug trace file could be closed twice, leading to
freeing already freed memory and a server crash.
* Trailing space removal for utf32 strings was done with
non-multibyte-safe code, leading to incorrect result length
and assertion failure.
* A malformed packet sent by the server when the query cache was
in use resulted in lost-connection errors.
* Multiple-statement execution could fail.
* CREATE TABLE failed if a column referred to in an index
definition and foreign key definition was in different
lettercases in the two definitions.
On behalf of the MySQL Build Team,
|• MySQL Community Server 5.5.7-rc has been released||Hery Ramilison||10 Nov|