This is a milestone release, for use at your own risk. Significant development changes take place in milestone releases and you may encounter compatibility issues, such as data format changes that require attention in addition to the usual procedure of running mysql_upgrade. For example, you may find it necessary to dump your data with mysqldump before the upgrade and reload it afterward.
Performance Schema Notes
The Performance Schema now includes instrumentation for table input and output. Instrumented operations include row-level accesses to persistent base tables or temporary tables. Operations that affect rows are fetch, insert, update, and delete. For a view, waits are associated with base tables referenced by the view.
Globally Unique Server IDs
Globally unique IDs for MySQL servers were implemented. A UUID
is now obtained automatically when the MySQL server starts. The
server first checks for a UUID written in the
auto.cnf file (in the server's data
directory), and uses this UUID if found. Otherwise, the server
generates a new UUID and saves it to this file (and creates the
file if it does not already exist). This UUID is available as
MySQL replication masters and slaves know each other's
UUIDs. The value of a slave's UUID can be read in the
SHOW SLAVE HOSTS. After
a slave is started using
SLAVE, the value of the master's UUID is
available on the slave in the output of
SHOW SLAVE STATUS.
(Bug #33815, Bug #11747723)
References: See also Bug #16927, Bug #11745543.
Functionality Added or Changed
It is now possible to exchange a partition of a partitioned
table or a subpartition of a subpartitioned table with a
nonpartitioned table that otherwise has the same structure using
ALTER TABLE ...
EXCHANGE PARTITION statement. This can be used, for
example, for importing and exporting partitions.
For more information and examples, see Exchanging Partitions and Subpartitions with Tables.
These unused and deprecated items have been removed: the
--rpl-recovery-rank options, the
rpl_recovery_rank system variable, and the
Rpl_status status variable.
(Bug #54649, Bug #11762095)
References: See also Bug #34437, Bug #11747900, Bug #34635, Bug #11747961.
SHOW SLAVE STATUS statement
now has a
Master_Info_File field indicating
the location of the
(Bug #50316, Bug #11758151)
MySQL now supports delayed replication such that a slave server
deliberately lags behind the master by at least a specified
amount of time. The default delay is 0 seconds. Use the new
MASTER_DELAY option for
CHANGE MASTER TO to set the delay
CHANGE MASTER TO MASTER_DELAY =
An event received from the master is not executed until at least
N seconds later than its execution on
SHOW SLAVE STATUS has three new
fields that provide information about the delay:
SQL_Delay: The number of seconds that the
slave must lag the master.
Waiting until MASTER_DELAY seconds after master
executed event, this field contains the number of
seconds left of the delay. At other times, this field is
Slave_SQL_Running_State: The state of the
SQL thread (analogous to
The value is identical to the
of the SQL thread as displayed by
When the slave SQL thread is waiting for the delay to elapse
before executing an event,
PROCESSLIST displays its
Waiting until MASTER_DELAY seconds after
master executed event.
relay-log.info file now contains the
delay value, so the file format has changed. See
Slave Status Logs. In particular, the first
line of the file now indicates how many lines are in the file.
If you downgrade a slave server to a version older than MySQL
5.6, the older server will not read the file correctly. To
address this, modify the file in a text editor to delete the
initial line containing the number of lines.
The introduction of delayed replication entails these restrictions:
statement could execute all types of events. Now it can
execute only format description events and row events.
The output from mysqlbinlog
--base64-output=ALWAYS cannot be parsed.
ALWAYS becomes an invalid value for this
option in 5.6.1.
For additional information, see Delayed Replication. (Bug #28760, Bug #11746794)
The Romansh locale
'rm_CH' is now a
permissible value for the
lc_time_names system variable.
(Bug #50915, Bug #11758678)
mysqlbinlog now has a
option to enable large row events to be read from binary log
mysqlbinlog now has the capability to back up
a binary log in its original binary format. When invoked with
mysqlbinlog connects to a server, requests
the log files, and writes output files in the same format as the
originals. See Using mysqlbinlog to Back Up Binary Log Files.
The Unicode character sets now have a
collation that provides DIN-2 (phone book) ordering (for
Unicode Character Sets.
Vietnamese collations were added for the Unicode character sets.
Those based on Unicode Collation Algorithm 5.2.0 have names of
based on Unicode Collation Algorithm 4.0.0 have names of the
collations are the same as the corresponding
collations except for precomposed characters which are accented
versions of “
U”. There is no change to
ideographic characters derived from Chinese. There are no
Unicode collation names now may include a version number to
indicate the Unicode Collation Algorithm (UCA) version on which
the collation is based. Initial collations thus created use
version UCA 5.2.0. For example,
utf8_unicode_520_ci is based on UCA 5.2.0.
UCA-based Unicode collation names that do not include a version
number are based on version 4.0.0.
UPPER() perform case folding
according to the collation of their argument. A character that
has uppercase and lowercase versions only in a Unicode version
more recent than 4.0.0 will be converted by these functions only
if the argument has a collation that uses a recent enough UCA
The LDML rules for creating user-defined collations are extended
to permit an optional
version attribute in
<collation> tags to indicate the UCA
version on which the collation is based. If the
version attribute is omitted, its default
Adding a UCA Collation to a Unicode Character Set.
In MySQL 5.5, setting
optimizer_search_depth to the
deprecated value of 63 switched to the algorithm used in MySQL
5.0.0 (and previous versions) for performing searches. The value
of 63 is now treated as invalid.
Security Fix: A security bug was fixed. (Bug #49124)
The server could crash on shutdown, if started with
(Bug #55581, Bug #11762927)
The internal flag indicating whether a user value was signed or
unsigned_flag) could sometimes
change between the time that the user value was recorded for
logging purposes and the time that the value was actually
written to the binary log, which could lead to inconsistency.
unsigned_flag is copied when the user
variable value is copied, and the copy of
unsigned_flag is then used for logging.
(Bug #51426, Bug #11759138)
References: See also Bug #49562, Bug #11757508.
The embedded server could crash when determining which directories to search for option files. (Bug #55062, Bug #11762465)
Performance Schema code was subject to a buffer overflow. (Bug #53363)
On Windows, an IPv6 connection to the server could not be made using an IPv4 address or host name. (Bug #52381, Bug #11760016)
Subquery execution for
could be done incorrectly and raise an assertion.
(Bug #52317, Bug #11759957)
There was a mixup between
GROUP BY and
ORDER BY concerning which indexes should be
considered or permitted during query optimization.
(Bug #52081, Bug #11759746)
On Windows, the
my_rename() function failed
to check whether the source file existed.
(Bug #51861, Bug #11759540)
ref column of
EXPLAIN output for subquery lines
could be missing information.
(Bug #50257, Bug #11758106)
statements were written to the binary log in cleartext rather
than in ciphertext.
BLACKHOLE storage engine failed to load
on Solaris and OpenSolaris if DTrace probes had been enabled.
(Bug #47748, Bug #11755909)
Some error messages included a literal
database name rather than a parameter for the database name.
(Bug #46792, Bug #11755079)
error message, the command name parameter could be truncated.
(Bug #45355, Bug #11753840)
On Windows, mysqlslap crashed for attempts to connect using shared memory. (Bug #31173, Bug #11747181, Bug #59107, Bug #11766072)
To forestall the occurrence of possible relocation errors in the
have been changed from normal libraries to “noinst”
libtool helper libraries, and are no longer
installed as separate libraries.
(Bug #29791, Bug #11746931)
A suboptimal query execution plan could be chosen when there
were several possible
ref accesses. Now
preference is given to the keys that match the most parts and
choosing the best one among them.
(Bug #26106, Bug #11746406)
Searches for data on a partial index for a column using the
utf8 character set failed.
For queries with
INDEX was not ignored as it should have been when it
would result in a more expensive query execution plan.
(Bug #18144, Bug #11745649)