MySQL 5.6 Release Notes
This release continues the process begun in MySQL 5.6.6 of making changes to the default values of server parameters. The motivation for these changes is to provide better out-of-box performance and to reduce the need for database administrators to change settings manually. These changes are subject to revision in future releases as we gain feedback.
In some cases, a parameter has a different fixed default value.
In other cases, the server autosizes a parameter at startup
using a formula based on other related parameters or server host
configuration, rather than using a fixed value. For example, the
setting for host_cache_size
is
its previous default of 128, adjusted up by an amount
proportional to the value of
max_connections
. The idea
behind autosizing is that when the server has information
available to make a decision about a parameter setting likely to
be better than a fixed default, it will.
The following table summarizes changes to defaults. For variables that are autosized, the main variable description provides additional detail about the sizing algorithm. See Server System Variables, and InnoDB Startup Options and System Variables. Any of these default settings can be overridden by specifying an explicit value at server startup.
Parameter | Old Default | New Default |
---|---|---|
host_cache_size |
128 | Autosized using max_connections |
innodb_log_file_size |
5MB |
48MB |
open_files_limit |
0 | Autosized using max_connections |
performance_schema |
OFF | ON |
performance_schema_events_waits_history_long_size |
10000 | Autosized |
performance_schema_events_waits_history_size |
10 | Autosize |
performance_schema_max_cond_instances |
1000 | Autosize |
performance_schema_max_file_instances |
10000 | Autosize |
performance_schema_max_mutex_instances |
1000000 | Autosize |
performance_schema_max_rwlock_instances |
1000000 | Autosize |
performance_schema_max_table_handles |
100000 | Autosize |
performance_schema_max_table_instances |
50000 | Autosize |
performance_schema_max_thread_instances |
1000 | Autosize |
query_cache_size |
0 | 1M |
query_cache_type |
ON |
OFF |
table_definition_cache |
400 | Autosized using table_open_cache |
table_open_cache |
400 | 2000 |
thread_cache_size |
0 | Autosized using max_connections |
mysql_install_db is now a Perl script and can be used on any system with Perl installed. Previously, it was a shell script and available only on Unix platforms.
In addition, mysql_install_db is more strict
about the --datadir
option value. Only the last component of the path name is
created if it does not exist; the parent directory must already
exist or an error occurs. Previously, it created any nonexistent
directories in the path name.
On Unix platforms, mysql_install_db now
creates a default option file named my.cnf
in the base installation directory. This file is created from a
template included in the distribution package named
my-default.cnf
. You can find the template
in or under the base installation directory. When started using
mysqld_safe, the server uses
my.cnf
file by default. If
my.cnf
already exists,
mysql_install_db assumes it to be in use and
writes a new file named my-new.cnf
instead.
With one exception, the settings in the default option file are
commented and have no effect. The exception is that the file
changes the sql_mode
system
variable from its default of
NO_ENGINE_SUBSTITUTION
to also
include STRICT_TRANS_TABLES
:
sql_mode=NO_ENGINE_SUBSTITUTION,STRICT_TRANS_TABLES
This setting produces a server configuration that results in errors rather than warnings for bad data in operations that modify transactional tables. See Server SQL Modes.
The my-default.cnf
template replaces the
older sample option files (my-small.cnf
,
my-medium.cnf
, and so forth), which are no
longer distributed.
On Unix platforms, mysql_install_db supports
a new option,
--random-passwords
,
that provides for more secure MySQL installation. Invoking
mysql_install_db with
--random-passwords
causes it to perform the following actions in addition to its
normal operation:
The installation process creates a random password, assigns
it to the initial MySQL root
accounts,
and sets the “password expired” flag for those
accounts.
The initial random root
password is
written to the .mysql_secret
file in
the directory named by the HOME
environment variable. Depending on operating system, using a
command such as sudo may cause the value
of HOME
to refer to the home directory of
the root
system user.
.mysql_secret
is created with mode 600
to be accessible only to the system user for whom it is
created.
If .mysql_secret
already exists, the
new password information is appended to it. Each password
entry includes a timestamp so that in the event of multiple
install operations it is possible to determine the password
associated with each one.
No anonymous-user MySQL accounts are created.
As a result of these actions, it is necessary after installation
to start the server, connect as root
using
the password written to the .mysql_secret
file, and to select a new root
password.
Until this is done, root
cannot do anything
else. This must be done for each root
account
you intend to use. To change the password, you can use the
SET PASSWORD
statement (for
example, with the mysql client). You can also
use mysqladmin or
mysql_secure_installation.
New RPM install operations (not upgrades) invoke
mysql_install_db with the
--random-passwords
option. As a consequence,
RPM installs from this version onward will have their
root
accounts secured, and will have no
anonymous-user accounts. (Install operations using RPMs for
Unbreakable Linux Network are unaffected because they do not use
mysql_install_db.)
For install operations using a binary
.tar.gz
distribution or a source
distribution, you can invoke mysql_install_db
with the --random-passwords
option manually to
make your MySQL installation more secure. This is recommended,
particularly for sites with sensitive data.
On Windows, many MySQL executables depend on the
libeay32.dll
and
ssleay32.dll
SSL libraries at runtime. To
ensure that the proper versions of these libraries are found,
the install process copies them into the same directory as the
executables.
InnoDB:
The InnoDB
transportable tablespace feature
was enhanced to allow ALTER TABLE ... IMPORT
TABLESPACE
to succeed in some cases where the
corresponding .cfg
file was not available.
This enhancement allows recovery of data even in some cases
where the system
tablespace is corrupted or deleted.
(Bug #14589582, Bug #66715)
The number of atomic operations performed by the Performance Schema was reduced. (Bug #14658739)
ALTER USER
now can be used as a
prepared statement.
(Bug #66874, Bug #14646014)
On Unix systems, the mysql client writes
statements executed interactively to a history file (see
mysql Client Logging). mysql now
ignores for logging purposes statements that match any pattern
in the “ignore” list. By default, the pattern list
is "*IDENTIFIED*:*PASSWORD*"
, to ignore
statements that refer to passwords. Pattern matching is not case
sensitive. Within patterns, two characters are special:
?
matches any single character.
*
matches any sequence of zero or more
characters.
To specify additional patterns, use the
--histignore
command option or set
the MYSQL_HISTIGNORE
environment variable.
(If both are specified, the option value takes precedence.) The
value should be a colon-separated list of one or more patterns,
which are appended to the default pattern list.
Patterns specified on the command line might need to be quoted
or escaped to prevent your command interpreter from treating
them specially. For example, to suppress logging for
UPDATE
and DELETE
statements in addition to statements that refer to passwords,
invoke mysql like this:
shell> mysql --histignore="*UPDATE*:*DELETE*"
(Bug #48287, Bug #11756377)
The SHOW AUTHORS
and SHOW
CONTRIBUTORS
statements have been removed.
Important Change; Replication:
When running the slave with the
--slave-skip-errors
option,
successive skipped events (errors logged as warnings) were found
to contain information from previous warnings, which caused an
excessive amount of redundant information to be written to the
error log. This problem could occur when using row-based or
mixed-format binary logging.
The fix for this issue is to clear these warnings prior to
processing the next skipped event. In addition, the skipped
events are now handled in the same way regardless of the value
of binlog_format
, and a skipped
error always causes a warning to be written to the error log, as
long as the value of the
log_warnings
system variable is
greater than 1.
(Bug #12776842)
Important Change:
The server system variables
profiling
,
have_profiling
, and
profiling_history_size
are now
deprecated, and are subject to removal in a future release of
the MySQL Server.
(Bug #14658683)
InnoDB:
The thread gathering
persistent
statistics for an InnoDB
table could
cause a serious error if it accessed the table while a
TRUNCATE TABLE
operation was in
progress:
InnoDB: Assertion failure in thread thread_num
in file fsp0fsp.cc line 1882
(Bug #14765035)
InnoDB:
When a CREATE INDEX
operation
failed for an InnoDB
FULLTEXT
index due to a duplicate key error,
some allocated memory was not freed.
(Bug #14759111)
InnoDB:
During a brief time window while creating an
InnoDB
unique index, MySQL could print a
spurious warning message:
WARNING: CANNOT FIND INDEX ?index_name
IN INNODB INDEX TRANSLATION TABLE
The cause was that MySQL started enforcing the uniqueness constraint before the existence of the index was fully registered. The fix suppresses the incorrect message during this final stage of index creation. (Bug #14735988)
InnoDB: An online DDL operation to create a unique index could fail to detect duplicate index values, when the duplicate values were caused by DML operations while the index was being created. (Bug #14733674)
InnoDB: During an online DDL operation, a duplicate key error could be incorrectly issued if a record was inserted and subsequently updated while the table was being rebuilt. (Bug #14723456)
InnoDB:
The auxiliary tables for FULLTEXT
indexes
were being created in the
system tablespace,
regardless of the setting for the
innodb_file_per_table
configuration option.
(Bug #14723291)
InnoDB:
When using the
transportable
tablespace feature, the ALTER TABLE ... IMPORT
TABLESPACE
statement could crash if the
InnoDB
table being flushed contained a
FULLTEXT
index. With this fix, the table data
can be imported, although you must drop and re-create the
FULLTEXT
index after the import operation.
(Bug #14712962, Bug #67081)
InnoDB:
An assertion failure occurred when a bogus duplicate key error
was flagged during online ALTER
TABLE
. This issue only occurred for a table that
lacked a primary key and
any secondary
indexes. This patch fixes the assertion failure, but not
the bogus duplicate key error, which is reported as
Bug#14723456.
(Bug #14712710)
InnoDB:
The InnoDB
memcached
plugin can now work with tables where the underlying character
set is multibyte.
(Bug #14711015, Bug #67076)
InnoDB:
If a CREATE TABLE
statement
failed due to a disk full error, some memory allocated during
the operation was not freed properly.
(Bug #14708715)
InnoDB:
An ALTER TABLE
operation on an
InnoDB
table containing a
FULLTEXT
index could cause make the server
halt with an assertion error. The fix causes all ALTER
TABLE
operations for such tables to use the
table-copying behavior of the ALGORITHM=COPY
clause.
(Bug #14681198)
InnoDB:
If the server crashed while executing
TRUNCATE TABLE
for an
InnoDB
table containing a
FULLTEXT
index, further errors could occur
during crash
recovery, preventing the server from restarting.
(Bug #14676345)
InnoDB:
If an InnoDB
table containing a
FULLTEXT
index was being modified by a
TRUNCATE TABLE
statement and on
online DDL operation
simultaneously, the server could end up with inconsistent
internal locks or could crash.
(Bug #14676329)
InnoDB:
If creation of a FULLTEXT
index failed
because of a “row too large” condition, a
subsequent ALTER TABLE
operation
could cause the server to halt with an error.
(Bug #14668777)
InnoDB:
If the MySQL server crashed while
XA transactions were in
PREPARED
state, inconsistent data could be
produced during crash
recovery if the query cache was enabled. The fix allows
MySQL to disable the query cache during crash recovery if
required.
(Bug #14658648)
InnoDB:
MySQL could crash while creating an InnoDB
table if the disk became full at a specific moment: after the
.frm file was created but
before the corresponding .ibd
file was created.
(Bug #14645935)
InnoDB: If the server crashed at the specific point when a change buffer entry was being merged into a buffer pool page, the transaction log and the change buffer were left in an inconsistent state. After a restart, MySQL could crash after reading the corresponding secondary index page. The problem was more likely to occur in MySQL 5.5 or later, where the original insert buffering mechanism was generalized to cover other operations. (Bug #14636528, Bug #66819, Bug #58571, Bug #61104, Bug #65443)
InnoDB:
If a crash occurred during a CREATE
TABLE
operation, the InnoDB
data dictionary
could be left in an inconsistent state, causing a crash if the
partially created table was accessed later.
(Bug #14601290)
InnoDB:
On startup, MySQL would not start if there was a mismatch
between the value of the
innodb_log_file_size
configuration option and the actual size of the
ib_logfile*
files that make up the
redo log. This behavior
required manually removing the redo log files after changing the
value of innodb_log_file_size
. The fix causes
MySQL to write all dirty
pages to disk and re-create the redo log files during
startup if it detects a size mismatch.
(Bug #14596550)
InnoDB:
With the innodb_file_per_table
setting enabled, a DROP TABLE
operation could cause a crash, due to a race condition that
depended on the timing of pending I/O requests.
(Bug #14594600, Bug #66718)
InnoDB: If an online DDL operation failed due to a duplicate key error, caused by DML changes being made concurrently to the table, the server could crash with an assertion error. (Bug #14591797)
InnoDB:
A query against an InnoDB
table with a
FULLTEXT
index could crash, if the
AGAINST
clause contained a character sequence
that was encoded incorrectly for the character set of the table.
(Bug #14588091)
InnoDB:
If a FULLTEXT
index was dropped from an
InnoDB
table, and the server crashed later
for an unrelated reason, an additional error could occur while
attempting to access nonexistent FULLTEXT
data structures.
(Bug #14586855)
InnoDB: The server could crash with a confusing message if it ran out of space for temporary files during index creation.
InnoDB: Assertion failure in thread thread_num
in file mtr0mtr.cc line 306
InnoDB: Failing assertion: mtr->state == 12231
(Bug #14586256)
InnoDB:
An ALTER TABLE
on an
InnoDB
table that dropped the primary key and
then re-created it with columns in a different order could cause
an error. The issue affected tables where the swapped columns
referenced each other in a single-table
foreign key
relationship. The data dictionary could be left in an
inconsistent state, where the table was listed in SHOW
TABLES
output but could not be queried or dropped. For
example, if the table was declared with primary key columns
(c1,c2)
and a foreign key with c1
REFERENCES c2
:
ALTER TABLE t2 DROP PRIMARY KEY, ADD PRIMARY KEY (c2, c1); ERROR 1030 (HY000): Got error 38 from storage engine
(Bug #14548753)
InnoDB:
During an online DDL operation, a
ROLLBACK
affecting the same table could cause an assertion error if the
table formerly contained a FULLTEXT
index.
Some bookkeeping information related to
FULLTEXT
indexes for
InnoDB
tables is preserved even after such an
index is dropped.
(Bug #14503700)
InnoDB: If a table was defined with an index key length very close to the upper length limit of 3072, a query against that table could cause a serious error. (Bug #14500557, Bug #14537695)
InnoDB:
Table names containing non-ASCII characters were displayed
incorrectly when the
MYSQL.INNODB_TABLE_STATS.TABLE_NAME
column
was queried.
(Bug #14404879)
InnoDB:
A race condition could cause a crash during an online
CREATE INDEX
statement for an
InnoDB
table. This bug only affected very
small tables. It required a DML
operation to be in progress for the table, affecting the
primary key columns, at
the same time the CREATE INDEX
statement was
issued.
(Bug #14117641)
InnoDB:
If a transaction was started with a consistent snapshot, then
new indexes were added to the table while the transaction was in
progress, a subsequent UPDATE
statement could
incorrectly encounter the error:
ER_TABLE_DEF_CHANGED: insufficient history for index
This issue could cause an assertion error in debug builds. (Bug #14036214)
InnoDB:
The server could crash with an assertion error during operations
on tables with ROW_FORMAT=COMPRESSED
.
(Bug #14001972)
InnoDB:
In rare circumstances, during operations on an
InnoDB
table containing
foreign keys, pages in
the buffer pool could be
evicted but not written to disk, leading to data inconsistency.
(Bug #13688491)
InnoDB:
In rare circumstances, MySQL could apply
InnoDB
undo
records out of order during a
ROLLBACK of an operation
that modified a BLOB column. This issue could cause an assertion
error in debug builds:
!bpage->file_page_was_freed
(Bug #13249921)
InnoDB:
In debug builds, a mismatch in the InnoDB
PAGE_FREE
list would cause an assertion.
(Bug #12701488)
Partitioning: The server now skips pruning of tables (see Partition Pruning) that use a storage engine which handles its own partitioning internally. The server now also explicitly rejects attempts to use explicit partitioning for such tables. (Bug #14672885)
Partitioning:
When used with a table having multiple columns in its primary
key, but partitioned by KEY
using a column
that was not part of the primary key as the partitioning column,
a query using an aggregate function and
DISTINCT
such as
SELECT
SUM
(DISTINCT
was not handled
correctly.
(Bug #14495351)pk_column_1
) FROM
table
WHERE
pk_column_2
=
constant
Replication: When using a multithreaded slave, if all worker threads were kept busy, it was possible for cleanup of an internal MTS circular buffer to fail, resulting in a full buffer and failure of the slave. (Bug #14710881)
Replication:
Executing FLUSH LOGS
in parallel
with COMMIT
could cause the
server to hang.
(Bug #14640486)
Replication:
When invoked while gtid_mode
was set to OFF
, the
SQL_THREAD_WAIT_AFTER_GTIDS()
function waited
indefinitely, unless a timeout was specified. In the latter
case, the function could return incorrect values. Now, when
gtid_mode
is OFF
,
SQL_THREAD_WAIT_AFTER_GTIDS()
always returns
NULL
, as expected.
(Bug #14640065)
Replication:
Partially-failed GRANT
and
REVOKE
statements were not always
handled the same way on the master and the slave. We now log an
incident event whenever an error occurs, even if it is only a
partial error, with a message stating that manual reconciliation
is required.
(Bug #14598585)
Replication:
There existed a gap in time between the appending of the current
GTID to the server's list of logged GTIDs and the commit of the
transaction by the storage engine. On slow platforms, or when
using profiling, this could cause
SELECT
SQL_THREAD_WAIT_AFTER_GTIDS(
to return before the data actually reached the database.
gtid
)
Now the current GTID is appended to the logged GTIDs following the commit, which removes this gap and so eliminates a possible source of inconsistency. (Bug #14116526)
Replication:
The error shown when a relay log file was missing from the relay
log index file informed the user only that the log file was not
found, but did not specify the exact reason. Now in such cases,
the error message returned is Could not find target
log file mentioned in relay log info in the index file
'index_file_name
' during relay log
initialization.
(Bug #11758505)
Replication: Following an insert into a nontransactional table that failed due to insufficient disk space, the server did not properly clean up all pending events, leading to an assert or possibly to other errors. (Bug #11750014)
Replication:
Backtick (`
) characters were not always
handled correctly in internally generated SQL statements, which
could sometimes lead to errors on replication slaves or cause
failure of restore operations from binary log files.
(Bug #66550, Bug #14548159, Bug #29422, Bug #11746883)
A DELETE
statement for an
InnoDB
table could write incorrect
transaction metadata into a record, causing the server to halt
with an error. To work around this issue, reduce the specified
length of the primary key to less than 1K bytes.
(Bug #14731482)
mysql_secure_installation could not change
the password for an account that had
password_expired='Y'
in the
mysql.user
table row for that account.
(Bug #14726722)
For an in-place ALTER TABLE
operation on an InnoDB
table that
produced a duplicate-key error for NULL
values, the error message displayed the column default value
rather than NULL
.
(Bug #14723364)
Patches for materialized semijoins caused failures of the query
plan interface used by NDBCLUSTER
.
(Bug #14704659)
mysqladmin password did not work for accounts with an expired password. (The fix for this problem is limited to accounts with passwords that use native or “old” native hashing. It still does not handle accounts that use SHA-256 password hashing.)
As a consequence of this patch, the restricted mode of operation
enforced by the server on operations permitted to clients with
expired passwords now includes
SET
statements in addition to SET
PASSWORD
. This is useful if the account uses a
password hashing format that requires
old_passwords
to be set to a
value different from its default.
(Bug #14698309)
Repeated execution of a query containing a subquery that used
MAX()
could result in increasing
memory consumption.
(Bug #14683676)
Queries that used a nested join with a subquery in the
FROM
clause and an ORDER BY ...
DESC
clause could return too few rows.
(Bug #14678404)
With the optimizer tracing enabled, the
INFORMATION_SCHEMA.OPTIMIZER_TRACE
table can be queried to find tracing information about the last
statements. However, for queries for which the results were
retrieved from the query cache, this information was not
available.
(Bug #14665052)
There was a performance regression for queries using
SELECT ... INTO
user variables and a
WHERE
condition on one or more of the
variables in the INTO
list.
(Bug #14664077)
References: This issue is a regression of: Bug #12408412.
In debug builds, the server could crash because
db_suicide()
failed to handle
SIGABRT
signals.
(Bug #14649493)
USE
could fail with
Unknown database when
dbname
dbname
contained multiple backtick
(`
) characters.
(Bug #14645196)
Outer joins could execute inefficiently and return incorrect results if joins were pushed down to the storage engine. (Bug #14644936)
A prepared statement that referenced views in an
IN
subquery could return different results
for different executions.
(Bug #14641759)
References: See also: Bug #13773979.
Within a stored program, memory allocated to hold condition information was not released until program exit, leading to excessive memory use. (Bug #14640599)
Attempts to insert, update, delete from, or lock unknown
Performance Schema tables failed with an
ER_TABLEACCESS_DENIED_ERROR
error rather than
ER_NO_SUCH_TABLE
.
(Bug #14633008)
An incomplete result could be stored in the query cache when a query failed with an error (providing that the query cache was enabled, and was set to a nonzero size). This fix ensures that it is no longer possible for queries that finish with an error to be cached. (Bug #14621700)
References: This issue is a regression of: Bug #40264.
The thread cache implementation worked in LIFO rather than FIFO fashion and could result in a thread being denied service (although this was a remote possibility). (Bug #14621627)
The server could crash when registering tables in the query cache for queries that selected from views. (Bug #14619935)
With semijoin and materialization optimizations enabled, a query
that materialized a const
table returned
incorrect results when STRAIGHT_JOIN
was
added.
(Bug #14609394)
Index condition pushdown in conjunction with descending index range scan could return incorrect results if there were multiple ranges in the range scan. (Bug #14604223)
EXPLAIN DELETE ...
WHERE
could function incorrectly when it was used in a stored routine.
(Bug #14601802)impossible_condition
References: This issue is a regression of: Bug #11752097.
Small values of max_sort_length
could produce incorrect results for integer, decimal,
floating-point, or temporal data types. Now
max_sort_length
is ignored for
those data types.
(Bug #14596888)
The configure.pl script that converts GNU
configure options to CMake
equivalents generated erroneous output for the
--with-client-ldflags
and
--with-mysqld-ldflags
options. It now ignores
those options.
(Bug #14593123)
A query with a subquery and ORDER BY
and
LIMIT
clauses returned fewer rows than
expected when executed using semijoin materialization.
(Bug #14580874)
The server printed excessive Got error 159 when reading
table
messages to the error log when one transaction
attempted to access a table that had been modified by another.
(Bug #14579877)
The optimizer could choose an incorrect execution plan for
updates to InnoDB
tables based on
indexes that use column prefixes.
(Bug #14578060)
Materialization of a subquery in the FROM
clause could return the wrong number of rows if the subquery
included a LIMIT
clause.
(Bug #14576727)
In-source builds modified the source file
sql/share/dictionary.txt
.
(Bug #14562699)
Improper memory cleanup could cause the server to exit. (Bug #14536113)
A query with a subquery in the JOIN ... ON
clause with an outer reference to a field that was out of scope
could cause the server to crash.
(Bug #14498914)
On Windows, mysql_plugin could not find my_print_defaults. (Bug #14471052)
When used in GRANT
statements,
quoted user name or host name values containing leading or
trailing spaces caused privileges to be assigned incorrectly
until a FLUSH PRIVILEGES
statement was issued.
Now, as a result of this fix, quoted name and host identifiers
used in a GRANT
statement are automatically
trimmed of any leading and trailing spaces, before privileges
are assigned.
(Bug #14328259)
Granting or revoking the PROXY
privilege caused the server to exit if the server was started
with the skip_name_resolve
system variable enabled.
(Bug #14211140)
CREATE USER
and
DROP USER
could fail to flush the
privileges, requiring FLUSH
PRIVILEGES
to be used explicitly.
(Bug #13864642)
On OS X, the
version_compile_machine
system
variable did not include the value 64
for
server binaries compiled on a 64-bit system.
(Bug #13859866)
Access to INFORMATION_SCHEMA
tables through a
view could leak memory.
(Bug #13734987)
On Microsoft Windows with CMake 2.6, the build process would not
stop if the create_initial_db
step failed.
(Bug #13713525)
The test in mysqld_safe for the presence of
the --plugin_dir
option and
assignment of a default value to it were performed before the
actual argument parsing took place.
(Bug #13548161)
A cached query result was not empty at the end of statement execution as expected. This could occur when executing queries (with the query cache enabled and set to a nonzero size) where the result was not sent to the client such as those executed by the Event Scheduler, or when executing stored routines containing queries while the server was running in bootstrap mode. (Bug #11755580, Bug #14609893)
The number of connection errors from a given host as counted by
the server was periodically reset, with the result that
max_connect_errors
was never
reached and invalid hosts were never blocked from trying to
connect.
(Bug #11753779)
References: See also: Bug #38247, Bug #43006, Bug #45584, Bug #45606.
The Range checked for each record
optimization is now used for conditions with outer query
references.
(Bug #11750963)
Random number generation during client authentication consumed excessive CPU. (Bug #66567, Bug #14555434)
Metadata locking resulted in excessive contention in read-only
workloads involving InnoDB
tables
and a low number of connections.
Now the set of metadata locks can be partitioned into separate
hashes to permit connections accessing different objects to use
different locking hashes and reduce contention. The new
metadata_locks_hash_instances
system variable can be used to specify the number of hashes.
(Bug #66473, Bug #14569140)
On Windows, the Perl version of mysql_install_db created system tables in the mysql database that were not populated properly. (Bug #65584, Bug #14181049)
ST_Contains()
and
ST_Within()
incorrectly reported that a
polygon did not contain itself. ST_Equals()
incorrectly returned 0 for polygons that differed only in
shifted vertices.
(Bug #64653, Bug #13864679)
ST_Difference()
could incorrectly produce
empty polygons in the result.
(Bug #64649, Bug #13865773)
libmysqlclient
did not use symbol versioning.
Thanks to Nicholas Bamber for the patch.
(Bug #64386, Bug #13788218)
The parser rejected legal queries that involved a
UNION
where the right hand side
query term has a table in parenthese.
(Bug #54382, Bug #11761854)
For some queries involving ORDER BY
, the
optimizer chose the wrong index for accessing the table.
(Bug #45969, Bug #11754370, Bug #14338686)
In debug builds, vio_read()
printed
errno
rather than
socket_error
to the debug trace.
(Bug #28775, Bug #11746795)