This is a milestone release, for use at your own risk. Upgrades between milestone releases (or from a milestone release to a GA release) are not supported. 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. (Making a backup before the upgrade is a prudent precaution in any case.)
Beginning with MySQL 5.6.5, Oracle no longer provides binaries for OS X 10.5. This aligns with Apple no longer providing updates or support for this platform.
Previously, at most one
TIMESTAMP
column per table could be automatically initialized or updated to the current date and time. This restriction has been lifted. AnyTIMESTAMP
column definition can have any combination ofDEFAULT CURRENT_TIMESTAMP
andON UPDATE CURRENT_TIMESTAMP
clauses. In addition, these clauses now can be used withDATETIME
column definitions. For more information, see Automatic Initialization and Updating for TIMESTAMP and DATETIME.
-
Important Change; Replication: This release introduces global transaction identifiers (GTIDs) for MySQL Replication. A GTID is a unique identifier that is assigned to each transaction as it is committed; this identifier is unique on the MySQL Server where the transaction originated, as well as across all MySQL Servers in a given replication setup. Because GTID-based replication depends on tracking transactions, it cannot be employed with tables that employ a nontransactional storage engine such as
MyISAM
; thus, it is currently supported only withInnoDB
tables.Because each transaction is uniquely identified, it is not necessary when using GTIDs to specify positions in the master's binary log when starting a new slave or failing over to a new master. This is reflected in the addition of a new
MASTER_AUTO_POSITION
option for theCHANGE MASTER TO
statement which takes the place of theMASTER_LOG_FILE
andMASTER_LOG_POS
options when executing this statement to prepare a MySQL Server to act as a replication slave.To enable GTIDs on a MySQL Server, the server must be started with the options
--gtid-mode=ON
--disable-gtid-unsafe-statements
--log-bin
--log-slave-updates
. These options are needed whether the server acts as a replication master or as a replication slave; the--gtid-mode
and--disable-gtid-unsafe-statements
options are new in this release. Once the master and slave have each been started with these options, it is necessary only to issue aCHANGE MASTER TO ... MASTER_AUTO_POSITION=1
followed bySTART SLAVE
on the slave to start replication.A number of new server system variables have also been added for monitoring GTID usage. For more information about these options and variables, see Global Transaction ID Options and Variables.
As part of these changes, three new mysqlbinlog options—
--include-gtids
,--exclude-gtids
, and--skip-gtids
—have been added for reading binary logs produced when the server participates in replication with GTIDs.ImportantDue to an issue discovered just prior to release, you cannot import a dump made using mysqldump from a MySQL 5.5 server to a MySQL 5.6.5 server and then use mysqlupgrade on the MySQL 5.6.5 server while GTIDs are enabled; doing so makes it impossible to connect to the server normally following the upgrade. Instead, you should import the dump and run mysqlupgrade while the MySQL 5.6.5 server is running with
--gtid-mode=OFF
, then restart it with--gtid-mode=ON
. (Bug #13833710) (mysqlupgrade can be executed when the server is running with--gtid-mode
set either toOFF
, or toON
.)For additional information about GTIDs and setting up GTID-based replication, see Replication with Global Transaction Identifiers.
-
MySQL now provides improved access to the host cache, which contains client IP address and host name information and is used to avoid DNS lookups, as well as more information about the causes of errors that occur when clients connect to the server. These changes have been implemented:
-
A new Performance Schema
host_cache
table exposes the contents of the host cache so that it can be examined usingSELECT
statements. Access to host cache contents makes it possible to answer questions such as how many hosts are cached, what kinds of connection errors are occurring for which hosts, or how close host error counts are to reaching themax_connect_errors
system variable limit. The Performance Schema must be enabled or this table is empty.If you upgrade to this MySQL release from an earlier version, you must run mysql_upgrade (and restart the server) to incorporate this change into the
performance_schema
database. The host cache has additional counters to track errors that do apply to specific IP addresses.
The host cache size now is configurable using the
host_cache_size
system variable. This variable also controls the maximum size of thehost_cache
table because that table is the cache visible representation. Setting the size to 0 disables the host cache. This is similar to disabling the cache by starting the server with--skip-host-cache
, but usinghost_cache_size
is more flexible because it can also be used to resize, enable, and disable the host cache at runtime, not just at server startup. If you start the server with--skip-host-cache
, the host cache cannot be re-enabled at runtime.New
Connection_errors_
status variables provide information about connection errors that do not apply to specific client IP addresses.xxx
For more information, see DNS Lookups and the Host Cache, and The host_cache Table. (Bug #22821, Bug #24906, Bug #45817, Bug #59404, Bug #11746048, Bug #11746269, Bug #11754244, Bug #11766316)
-
Reporting of how to sort a result set in
EXPLAIN
has been improved for some statements. This sorting decision could be reported incorrectly, causingUsing filesort
orUsing temporary
to be reported when they should not have been or vice versa. This could occur for statements that included index hints, that had the formSELECT SQL_BIG_RESULT ... GROUP BY
, that usedSQL_CALC_FOUND_ROWS
withLIMIT
, or that usedGROUP BY
,ORDER BY
, andLIMIT
. (Bug #11744768, Bug #1560)-
These query optimizer improvements were implemented:
-
The
EXPLAIN
statement now can produce output in JSON format. To select this, useEXPLAIN FORMAT = JSON
syntax. Withexplainable_stmt
FORMAT = JSON
, the output includes regularEXPLAIN
information, as well as extended and partition information.Traditional
EXPLAIN
output has also changed so that empty columns containNULL
rather the empty string. In addition,UNION RESULT
rows haveUsing filesort
in theExtra
column because a temporary table is used to bufferUNION
results.To work for both Optimizer Trace and JSON-format
EXPLAIN
output, theend_marker
parameter for theoptimizer_trace
system variable has been moved to a separateend_markers_in_json
system variable. This is an incompatible change to theoptimizer_trace
variable. For more information, see MySQL Internals: Tracing the Optimizer. -
The optimizer tries to find the best query execution plan by beginning with the most promising table and recursively adding to the plan the most promising of the remaining tables. Partial execution plans with a higher cost than an already found plan are pruned. The optimizer now attempts to improve the order in which it adds tables to the plan, resulting in a reduction of the number of partial plans considered.
Queries that are likely to have improved performance are joins of many tables, where most tables use
eq_ref
orref
join types (as indicated byEXPLAIN
output).A new status variable,
Last_query_partial_plans
, counts the number of iterations the optimizer makes in execution plan construction for the previous query. -
The optimizer uses semijoin and materialization strategies to optimize subquery execution. See Optimizing Subqueries with Semijoin Transformations, and Optimizing Subqueries with Materialization. In addition, the Batched Key Access (BKA) Join and Block Nested-Loop (BNL) Join algorithms used for inner join and outer join operations have been extended to support semijoin operations. For more information, see Block Nested-Loop and Batched Key Access Joins.
Several flags have been added to the
optimizer_switch
system variable to enable control over semijoin and subquery materialization strategies. Thesemijoin
flag controls whether semijoins are used. If it is set toon
, thefirstmatch
andloosescan
flags enable finer control over the permitted semijoin strategies. Thematerialization
flag controls whether subquery materialization is used. Ifsemijoin
andmaterialization
are bothon
, semijoins also use materialization where applicable. These flags areon
by default. See Switchable Optimizations. For expressions such as
that compare a column to a list of values, the optimizer previously made row estimates using index dives for each value in the list. This becomes inefficient as the number of values becomes large. The optimizer now can make row estimates for such expressions using index statistics instead, which is less accurate but quicker for a large number of values. The point at which the optimizer switches from index dives to index statistics is configurable using the newcol_name
IN(values
)eq_range_index_dive_limit
system variable. For more information, see Equality Range Optimization of Many-Valued Comparisons.
-
-
The Performance Schema has these additions:
The Performance Schema now has a
host_cache
table that exposes the contents of the host cache so that it can be examined usingSELECT
statements. See Host Cache Notes elsewhere in this changelog.-
The Performance Schema now maintains statement digest information. This normalizes and groups statements with the same “signature” and permits questions to be answered about the types of statements the server is executing and how often they occur.
A
statement_digest
consumer in thesetup_consumers
table controls whether the Performance Schema maintains digest information.The statement event tables (
events_statements_current
,events_statements_history
, andevents_statements_history_long
) haveDIGEST
andDIGEST_TEXT
columns that contain digest MD5 values and the corresponding normalized statement text strings.A
events_statements_summary_by_digest
table provides aggregated statement digest information.
For more information, see The host_cache Table, Performance Schema Statement Event Tables, and Statement Summary Tables.
If you upgrade to this MySQL release from an earlier version, you must run mysql_upgrade (and restart the server) to incorporate these changes into the
performance_schema
database.
Passwords stored in the older hash format used before MySQL 4.1 are less secure than passwords that use the native password hashing method and should be avoided. Pre-4.1 passwords and the
mysql_old_password
authentication plugin are now deprecated. To prevent connections using accounts that have pre-4.1 password hashes, thesecure_auth
system variable is now enabled by default. (To permit connections for accounts that have such password hashes, start the server with--secure_auth=0
.) (Bug #13586336)MySQL client programs now issue a warning if a password is given on the command line that this can be insecure.
Incompatible Change: The obsolete
OPTION
modifier for theSET
statement has been removed.InnoDB:
--ignore-builtin-innodb
is now ignored if used. (Bug #13586262)OS X; Microsoft Windows: A new CMake option,
MYSQL_PROJECT_NAME
, can be set on Windows or OS X to be used in the project name. (Bug #13551687)Microsoft Windows: A new server option,
--slow-start-timeout
, controls the Windows service control manager's service start timeout. The value is the maximum number of milliseconds that the service control manager waits before trying to kill the MySQL service during startup. The default value is 15000 (15 seconds). If the MySQL service takes too long to start, you may need to increase this value. A value of 0 means there is no timeout. (Bug #45546, Bug #11754011)The
MySQL-shared-compat
RPM package enables users of Red Hat-providedmysql-*-5.1
RPM packages to migrate to Oracle-providedMySQL-*-5.5
packages.MySQL-shared-compat
now replaces the Red Hatmysql-libs
package by replacinglibmysqlclient.so
files of the latter package, thus satisfying dependencies of other packages onmysql-libs
. This change affects only users of Red Hat (or Red Hat-compatible) RPM packages. Nothing is different for users of Oracle RPM packages. (Bug #13867506)Temporary tables for
INFORMATION_SCHEMA
queries now use dynamicMyISAM
row format if they contain sufficiently largeVARCHAR
columns, resulting in space savings. (Bug #13627632)As of MySQL 5.5.3, the
LOW_PRIORITY
modifier forLOCK TABLES ... LOW_PRIORITY WRITE
has no effect. This modifier is now deprecated. Its use should be avoided and now produces a warning. UseLOCK TABLES ... WRITE
instead. (Bug #13586314)If the
log_queries_not_using_indexes
system variable is enabled, slow queries that do not use indexes are written to the slow query log. In this case, it is now possible to put a logging rate limit on these queries by setting the newlog_throttle_queries_not_using_indexes
system variable, so that the slow query log does not grow too quickly. By default, this variable is 0, which means there is no limit. Positive values impose a per-minute limit on logging of queries that do not use indexes. The first such query opens a 60-second window within which the server logs queries up to the given limit, then suppresses additional queries. If there are suppressed queries when the window ends, the server logs a summary that indicates how many there were and the aggregate time spent in them. The next 60-second window begins when the server logs the next query that does not use indexes. (Bug #55323, Bug #11762697)Several subquery performance issues were resolved through the implementation of semijoin subquery optimization strategies. See Optimizing Subqueries with Semijoin Transformations. (Bug #47914, Bug #11756048, Bug #58660, Bug #11765671, Bug #10815, Bug #11745162, Bug #9021, Bug #13519134, Bug #48763, Bug #11756798, Bug #25130, Bug #11746289)
The mysql client now supports an
--init-command=
option. The option value is an SQL statement to execute after connecting to the server. If auto-reconnect is enabled, the statement is executed again after reconnection occurs. (Bug #45634, Bug #11754087)str
-
New
utf8_general_mysql500_ci
anducs2_general_mysql500_ci
collations have been added that preserve the behavior ofutf8_general_ci
anducs2_general_ci
from versions of MySQL previous to 5.1.24. Bug #27877 corrected an error in the original collations but introduced an incompatibility for columns that contain German'ß'
LATIN SMALL LETTER SHARP S. (As a result of the fix, that character compares equal to characters with which it previously compared different.) A symptom of the problem after upgrading to MySQL 5.1.24 or newer from a version older than 5.1.24 is thatCHECK TABLE
produces this error:Table upgrade required. Please do "REPAIR TABLE `t`" or dump/reload to fix it!
Unfortunately,
REPAIR TABLE
could not fix the problem. The new collations permit older tables created before MySQL 5.1.24 to be upgraded to current versions of MySQL.To convert an affected table after a binary upgrade that leaves the table files in place, alter the table to use the new collation. Suppose that the table
t1
contains one or more problematicutf8
columns. To convert the table at the table level, use a statement like this:ALTER TABLE t1 CONVERT TO CHARACTER SET utf8 COLLATE utf8_general_mysql500_ci;
To apply the change on a column-specific basis, use a statement like this (be sure to repeat the column definition as originally specified except for the
COLLATE
clause):ALTER TABLE t1 MODIFY c1 CHAR(N) CHARACTER SET utf8 COLLATE utf8_general_mysql500_ci;
To upgrade the table using a dump and reload procedure, dump the table using mysqldump, modify the
CREATE TABLE
statement in the dump file to use the new collation, and reload the table.After making the appropriate changes,
CHECK TABLE
should report no error. (Bug #43593, Bug #11752408)References: See also: Bug #27877.
-
The
SET TRANSACTION
andSTART TRANSACTION
statements now supportREAD WRITE
andREAD ONLY
modifiers to set the transaction access mode for tables used in transactions. The default mode is read/write, which is the same mode as previously. Read/write mode now may be specified explicitly with theREAD WRITE
modifier. UsingREAD ONLY
prohibits table changes and may enable storage engines to make performance improvements that are possible when changes are not permitted.In addition, the new
--transaction-read-only
option andtx_read_only
system variable permit the default transaction access mode to be set at server startup and runtime.For more information, see SET TRANSACTION Statement, and START TRANSACTION, COMMIT, and ROLLBACK Statements.
MySQL distributions no longer include the GPL
readline
input-editing library. This results in simpler maintenance and support, and simplifies licensing considerations.
Incompatible Change; Replication:
CHANGE MASTER TO
statements were written into the error log using quoted numeric values, although the syntax for this statement does not allow such option values to be quoted. This meant that such statements could not be copied from the error log and re-run verbatim. NowCHANGE MASTER TO
statements are written to the error log without the extraneous quotation marks, and so are syntactically correct as logged.Incompatible Change: A change in MySQL 5.6.3 caused
LAST_DAY()
to be more strict and reject incomplete dates with a day part of zero. For this function, a nonzero day part is not necessary, so the change has been reverted. (Bug #13458237)-
Important Change; InnoDB: When a row grew in size due to an
UPDATE
operation, other (non-updated) columns could be moved to off-page storage so that information about the row still fit within the constraints of theInnoDB
page size. The pointer to the new allocated off-page data was not set up until the pages were allocated and written, potentially leading to lost data if the system crashed while the column was being moved out of the page. The problem was more common with tables usingROW_FORMAT=DYNAMIC
orROW_FORMAT=COMPRESSED
along with the Barracuda file format, particularly with theinnodb_file_per_table
setting enabled, because page allocation operations are more common as the.ibd
tablespace files are extended. Still, the problem could occur with any combination of InnoDB version, file format, and row format.A related issue was that during such an
UPDATE
operation, or anINSERT
operation that reused a delete-marked record, other transactions could see invalid data for the affected column, regardless of isolation level.The fix corrects the order of operations for moving the column data off the original page and replacing it with a pointer. Now if a crash occurs at the precise moment when the column data is being transferred, the transfer will not be re-run during crash recovery.
In MySQL 5.1, this fix applies to the InnoDB Plugin, but not the built-in InnoDB storage engine. (Bug #13721257, Bug #12612184, Bug #12704861)
Important Change; Partitioning: The query cache did not always function correctly with partitioned tables in a transactional context. For this reason, the query cache is now disabled for any queries using partitioned tables, and such queries can no longer be cached. For more information, see Restrictions and Limitations on Partitioning. (Bug #11761296, Bug #53775)
Important Change; Replication: The
CHANGE MASTER TO
statement was not checked for invalid characters in values for options such asMASTER_HOST
andMASTER_USER
. In addition, when the server was restarted, a value containing certain characters was trimmed, causing the loss of its original value. Now such values are validated, and in cases where the value contains invalid characters, including linefeed (\n
or0x0A
) characters, the statement fails with an error (ER_MASTER_INFO
). (Bug #11758581, Bug #50801)-
Important Change; Replication: Moving the binary log file, relay log file, or both files to a new location, then restarting the server with a new value for
--log-bin
,--relay-log
, or both, caused the server to abort on start. This was because the entries in the index file overrode the new location. In addition, paths were calculated relative to datadir (rather than to the--log-bin
or--relay-log
values).The fix for this problem means that, when the server reads an entry from the index file, it now checks whether the entry contains a relative path. If it does, the relative part of the path is replaced with the absolute path set using the
--log-bin
or--relay-log
option. An absolute path remains unchanged; in such a case, the index must be edited manually to enable the new path or paths to be used. (Bug #11745230, Bug #12133) Performance; InnoDB: The optimizer now takes into account
InnoDB
page sizes other than 16KB, which can be configured with theinnodb_page_size
option when creating a MySQL instance. This change improves the estimates of I/O costs for queries on systems with non-defaultInnoDB
page sizes. (Bug #13623078)Performance; InnoDB: Memory allocation for
InnoDB
tables was reorganized to reduce the memory overhead for large numbers of tables or partitions, avoiding situations where the “resident set size” could grow regardless ofFLUSH TABLES
statements. The problem was most evident for tables with large row size. Some of the memory that was formerly allocated for every open table is now allocated only when the table is modified for the first time. (Bug #11764622, Bug #57480)Performance: Temporary
MyISAM
tables (unlike normalMyISAM
tables) did not use the dynamic row format when they containedVARCHAR
columns, resulting in larger temporary files (and more file I/O) than necessary. Dynamic row format now is used, which results in smaller tables that are faster to process. (Bug #13350136, Bug #78840, Bug #22023218)InnoDB: An erroneous assertion could occur, in debug builds only, when creating an index on a column containing zero-length values (that is,
''
). (Bug #13654923)InnoDB: A DDL operation such as
ALTER TABLE ... ADD COLUMN
could stall, eventually timing out with anError 1005: Can't create table
message referring tofil_rename_tablespace
. (Bug #13636122, Bug #62100, Bug #63553)InnoDB: If InnoDB was started with
innodb_force_recovery
set to a value of 3 or 4, and there are transactions to roll back, normal shutdown would hang waiting for those transactions to complete. Now the shutdown happens immediately, without rolling back any transactions, because nonzero values forinnodb_force_recovery
are only appropriate for troubleshooting and diagnostic purposes. (Bug #13628420)InnoDB: The MySQL server could hang in some cases if the configuration option
innodb_use_native_aio
was turned off. (Bug #13619598)InnoDB: A Valgrind error was fixed in the function
os_aio_init()
. (Bug #13612811)InnoDB: The configuration option
innodb_sort_buf_size
was renamed toinnodb_sort_buffer_size
for consistency. This work area is used while creating anInnoDB
index. (Bug #13610358)-
InnoDB: The server could crash when creating an
InnoDB
temporary table under Linux, if the$TMPDIR
setting points to atmpfs
filesystem andinnodb_use_native_aio
is enabled, as it is by default in MySQL 5.5.4 and higher. The entry in the error log looked like:101123 2:10:59 InnoDB: Operating system error number 22 in a file operation. InnoDB: Error number 22 means 'Invalid argument'.
The crash occurred because asynchronous I/O is not supported on tmpfs in some Linux kernel versions. The workaround was to turn off the
innodb_use_native_aio
setting or use a different temporary directory. The fix causesInnoDB
to turn off theinnodb_use_native_aio
setting automatically if it detects that the temporary file directory does not support asynchronous I/O. (Bug #13593888, Bug #11765450, Bug #58421) InnoDB: During startup, the status variable
Innodb_buffer_pool_dump_status
could be empty for a brief time before being initialized to the correct valuenot started
. (Bug #13513676)InnoDB: Valgrind errors when referencing the internal function
buf_LRU_scan_and_free_block()
were fixed. (Bug #13491704)-
InnoDB: The MySQL error log could contain messages like:
InnoDB: Ignoring strange row from mysql.innodb_index_stats WHERE ...
The fix makes the contents of the
innodb_index_stats
andinnodb_table_stats
tables case-sensitive, to properly distinguish the statistics for tables whose names differ only in lettercase. Other cases were fixed where the wrong name could be selected for an index while retrieving persistent statistics. (Bug #13432465) InnoDB: References to C preprocessor symbols and macros
HAVE_purify
,UNIV_INIT_MEM_TO_ZERO
, andUNIV_SET_MEM_TO_ZERO
were removed from theInnoDB
source code. They were only used in debug builds instrumented for Valgrind. They are replaced by calls to theUNIV_MEM_INVALID()
macro. (Bug #13418934)-
InnoDB: The MySQL server could halt with an assertion error:
InnoDB: Failing assertion: page_get_n_recs(page) > 1
Subsequent restarts could fail with the same error. The error occurred during a purge operation involving the
InnoDB
change buffer. The workaround was to set the configuration optioninnodb_change_buffering=inserts
. (Bug #13413535, Bug #61104) InnoDB: A discrepancy could arise between the number of available
InnoDB
undo logs and the number of undo logs that were currently active. Now theinnodb_undo_logs
system variable reports the number of active undo logs, and the newInnodb_available_undo_logs
status variable reports the total number of undo logs. (Bug #13255225)InnoDB: When doing a live downgrade from MySQL 5.6.4 or later, with
innodb_page_size
set to a value other than 16384, now the earlier MySQL version reports that the page size is incompatible with the older version, rather than crashing or displaying a “corruption” error. (Bug #13116225)InnoDB: Certain
CREATE TABLE
statements could fail forInnoDB
child tables containing foreign key definitions. This problem affected Windows systems only, with the settinglower_case_table_names=0
. It was a regression from MySQL bug #55222. (Bug #13083023, Bug #60229)-
InnoDB: If the server crashed during a
TRUNCATE TABLE
orCREATE INDEX
statement for anInnoDB
table, or aDROP DATABASE
statement for a database containingInnoDB
tables, an index could be corrupted, causing an error message when accessing the table after restart:InnoDB: Error: trying to load index index_name for table table_name InnoDB: but the index tree has been freed!
In MySQL 5.1, this fix applies to the InnoDB Plugin, but not the built-in InnoDB storage engine. (Bug #12861864, Bug #11766019)
-
InnoDB: A DDL operation for an
InnoDB
table could cause a busy MySQL server to halt with an assertion error:InnoDB: Failing assertion: trx->error_state == DB_SUCCESS
The error occurred if the DDL operation was run while all 1023 undo slots were in use by concurrent transactions. This error was less likely to occur in MySQL 5.5 and 5.6, because raising the number of
InnoDB
undo slots increased the number of simultaneous transactions (corresponding to the number of undo slots) from 1K to 128K. (Bug #12739098, Bug #62401) InnoDB:
InnoDB
persistent statistics gave less accurate estimates for date columns than for columns of other data types. The fix changes the way cardinality is estimated for nonunique keys, and avoids situations where identical values could be counted twice if they occurred on different index pages. (Bug #12429443)-
InnoDB: The
innodb_max_purge_lag
variable controls how to delay DML operations when purge operations are lagging. Previously, if an old consistent read view was detected, DML operations would not be delayed even though the purge lag exceeded theinnodb_max_purge_lag
setting.Additionally, if the
innodb_max_purge_lag
setting was used, situations could arise in which the DML delay time would continue to increase but not be applied right away due to the presence an old consistent read view. This could result in a lengthy DML delay when the accumulated DML delay time is eventually applied.This fix caps the DML delay at a maximum value, removes the consistent read check, and revises the DML delay calculation. (Bug #12407434, Bug #60776)
-
InnoDB: With 1024 concurrent
InnoDB
transactions running concurrently and theinnodb_file_per_table
setting enabled, aCREATE TABLE
operation for anInnoDB
table could fail. The.ibd
file from the failedCREATE TABLE
was left behind, preventing the table from being created later, after the load had dropped.The fix adds error handling to delete the erroneous
.ibd
file. This error was less likely to occur in MySQL 5.5 and 5.6, because raising the number ofInnoDB
undo slots increased the number of simultaneous transactions needed to trigger the bug, from 1K to 128K. (Bug #12400341) InnoDB: Improved the accuracy of persistent
InnoDB
statistics for large tables. The estimate of distinct records could be inaccurate if the index tree was more than 3 levels deep. (Bug #12316365)-
InnoDB: Shutdown could hang with messages like this in the log:
Waiting for purge thread to be suspended
After 1 hour, the shutdown times out and
mysqld
quits. This problem is most likely to occur with a high value forinnodb_purge_threads
. (Bug #11765863, Bug #58868, Bug #60939) -
InnoDB: When
DROP TABLE
failed due to all undo slots being in use, the error returned was Unknown table '...' rather than the expected Too many active concurrent transactions. (Bug #11764724, Bug #57586)References: See also: Bug #11764668, Bug #57529.
-
InnoDB: Server startup could produce an error for temporary tables using the
InnoDB
storage engine, if the path in the$TMPDIR
variable ended with a/
character. The error log would look like:120202 19:21:26 InnoDB: Operating system error number 2 in a file operation. InnoDB: The error means the system cannot find the path specified. InnoDB: If you are installing InnoDB, remember that you must create InnoDB: directories yourself, InnoDB does not create them. 120202 19:21:26 InnoDB: Error: trying to open a table, but could not InnoDB: open the tablespace file './t/#sql7750_1_0.ibd'! InnoDB: Have you moved InnoDB .ibd files around without using the InnoDB: commands DISCARD TABLESPACE and IMPORT TABLESPACE? InnoDB: It is also possible that this is a temporary table #sql..., InnoDB: and MySQL removed the .ibd file for this.
The workaround for the problem was to create a similar temporary table again, copy its
.frm
file totmpdir
under the name mentioned in the error message (for example,#sql123.frm
) and restartmysqld
withtmpdir
set to its normal value without a trailing slash, for example/var/tmp
. On startup, MySQL would see the.frm
file and issueDROP TABLE
for the orphaned temporary table. (Bug #11754376, Bug #45976) Partitioning: When creating a view from a
SELECT
statement that used explicit partition selection, the partition selection portion of the query was ignored. (Bug #13559657)-
Partitioning: Adding a partition to an already existing
LIST
-partitioned table did not work correctly if the number of items in the new partition was greater than 16. This could happen when trying to add a partition using anALTER TABLE ... ADD PARTITION
statement, or anALTER TABLE ... REORGANIZE PARTITION
statement.This 16-item limit was not apparent when using either
CREATE TABLE ... PARTITION BY LIST
orALTER TABLE ... PARTITION BY LIST
. (Bug #13029508, Bug #62505) -
Partitioning: A function internal to the code for finding matching subpartitions represented an unsigned number as signed, with the result that matching subpartitions were sometimes missed in results of queries. (Bug #12725206, Bug #61765)
References: See also: Bug #20257.
Partitioning: An
ALTER TABLE ... ADD PARTITION
statement subsequent toALTER TABLE ... REORGANIZE PARTITION
failed on a table partitioned byHASH
orKEY
. (Bug #11764110, Bug #56909)-
Replication: Executing mysqlbinlog with the
--start-position=
option, whereN
N
was equal either to 0 or to a value greater than the length of the dump file, caused it to crash.This issue was introduced in MySQL 5.5.18 by the fix for Bug #32228 and Bug #11747416. (Bug #13593869, Bug #64035)
References: This issue is a regression of: Bug #32228, Bug #11747416.
-
Replication: When starting the server, replication repositories were checked even when the
server_id
system variable was equal to 0 (the default), in spite of the fact that a valid nonzero value forserver_id
must be supplied for a server that acts as either a master or a slave in MySQL replication.This could cause problems when trying to perform a live upgrade from MySQL 5.5, although it was possible to work around the issue by starting the server with
--skip-slave-start
(in addition to any other required options).To avoid this problem, replication repositories are now checked only when the server is started with
--server-id
using a nonzero value. (Bug #13427444, Bug #13504821) Replication: Formerly, the default value shown for the
Port
column in the output ofSHOW SLAVE HOSTS
was 3306 whether the port had been set incorrectly or not set at all. Now, when the slave port is not set, the actual port used by the slave is shown. This change also affects the default shown for the--report-port
server option. (Bug #13333431)Replication: A race condition could occur when running multiple instances of mysqld on a single machine, when more than slave thread was started at the same time, and each such thread tried to use the same temporary file concurrently. (Bug #12844302, Bug #62055)
-
Replication: It was possible on replication slaves where
FEDERATED
tables were in use to get timeouts on long-running operations, such as Error 1160 Got an error writing communication packets. TheFEDERATED
tables did not need to be replicated for the issue to occur. (Bug #11758931, Bug #51196)References: See also: Bug #12896628, Bug #61790.
Replication: Statements that wrote to tables with
AUTO_INCREMENT
columns based on an unorderedSELECT
from another table could lead to the master and the slave going out of sync, as the order in which the rows are retrieved from the table may differ between them. Such statements include anyINSERT ... SELECT
,REPLACE ... SELECT
, orCREATE TABLE ... SELECT
statement. Such statements are now marked as unsafe for statement-based replication, which causes the execution of one to throw a warning, and forces the statement to be logged using the row-based format if the logging format isMIXED
. (Bug #11758263, Bug #50440)Replication: On Windows replication slave hosts,
STOP SLAVE
took an excessive length of time to complete when the master was down. (Bug #11752315, Bug #43460)-
Replication: mysqlbinlog
--database=
included alldbname
SET INSERT_ID=
assignments from the binary log in its output, even if databasen
dbname
was never referenced in the binary log. This was due to the fact thatCOMMIT
statements were not associated with any database in the binary log. Now in such cases, the current database is tracked so that only thoseSET INSERT_ID
assignments that are made in the context of changes to tables in databasedbname
are actually printed in the mysqlbinlog output. (Bug #11746146, Bug #23894)References: See also: Bug #23890, Bug #46998, Bug #11761686, Bug #54201, Bug #11754117, Bug #45670.
Microsoft Windows: On Windows, rebuilds in a source distribution failed to create the initial database due to insufficient cleanup from the previous run or failure to find the proper server executable. (Bug #13431251)
Microsoft Windows: On Windows, the server incorrectly constructed the full path name of the plugin binary for
INSTALL PLUGIN
andCREATE FUNCTION ... SONAME
. (Bug #45549, Bug #11754014)mysqldump tried to execute
SET
statements asSET OPTION
, which failed when used against 5.6 or higher servers because the deprecatedOPTION
keyword has been removed fromSET
syntax. (Bug #13813473)The optimizer did not perform constant propagation for views, so a query containing views resulted in a less efficient execution plan than the corresponding query using only base tables. (Bug #13783777)
A memory leak could occur for queries containing a subquery that used
GROUP BY
on an outer column. (Bug #13724099)-
After using an
ALTER TABLE
statement to change theKEY_BLOCK_SIZE
property for anInnoDB
table, for example when switching from an uncompressed to a compressed table, subsequent server restarts could fail with a message like:InnoDB: Error: data file path/ibdata2 uses page size 1024, InnoDB: but the only supported page size in this release is=16384
This issue is a regression introduced in MySQL 5.5.20. (Bug #13698765, Bug #64160)
In debug builds, a Debug Sync timeout warning was treated as an error, causing an assertion to be raised. (Bug #13688248)
_mi_print_key()
iterated one time too many when there was aNULL
bit, resulting in Valgrind warnings. (Bug #13686970)Pushing down to
InnoDB
an index condition that called a stored function resulted in a server crash. This kind of condition is no longer pushed down. (Bug #13655397)A
SELECT
from a subquery that returned an empty result could itself fail to return an empty result as expected. (Bug #13651009, Bug #13650418)For debug builds, negative values with a zero integer part and nonzero fractional part (such as -0.1111) were not detected, so the negative fractional part was later cast to a large unsigned number and raised an assertion. (Bug #13616434)
If during server startup a signal such as
SIGHUP
was caught prior to full server initialization, the server could crash. This was due to a race condition between the signal handler thread and the main thread performing server initialization. To prevent this from happening, signal processing is now suspended until full initialization of all server subsystems has been completed successfully. (Bug #13608371, Bug #62311)The shared version of
libmysqlclient
did not export these functions for linking by client programs:get_tty_password()
,handle_options()
,my_print_help()
. (Bug #13604121)An aggregated expression of type
MIN()
orMAX()
should returnNULL
but could instead return the empty set if the query was implicitly grouped and there was noHAVING
clause that evaluates toFALSE
. (Bug #13599013)Left join queries could be incorrectly converted to inner joins and return erroneous result sets. (Bug #13595212)
Date-handling code could raise an assertion attempting to calculate the number of seconds since the epoch. (Bug #13545236)
For queries that used a join type of
ref_or_null
, the optimizer could skip the filesort operation and sort the results incorrectly. (Bug #13531865)For some queries, a filesort operation was done even when the result contained only a single row and needed no sorting. (Bug #13529048)
The optimizer could return an incorrect select limit in some cases when a query included no explicit
LIMIT
clause. (Bug #13528826)In some cases, the optimizer failed to use a covering index when that was possible and read data rows instead. (Bug #13514959)
-
SELECT
statements failed for theEXAMPLE
storage engine. (Bug #13511529)References: This issue is a regression of: Bug #11746275.
The Performance Schema instrumentation for stages did not fully honor the
ENABLED
column in theschema.setup_instruments
table. (Bug #13509513)Converting a string ending with a decimal point (such as
'1.'
) to a floating-point number raised a data truncation warning. (Bug #13500371)Use of an uninitialized
TABLE_SHARE
member could cause a server crash. (Bug #13489996)Some outer joins that used views as inner tables did not evaluate conditions correctly. (Bug #13464334)
A query that used an index on a
CHAR
column referenced in aBETWEEN
clause could return invalid results. (Bug #13463488, Bug #63437)Expressions that compared a
BIGINT
column with any non-integer constant were performed using integers rather than decimal or float values, with the result that the constant could be truncated. This could lead to any such comparison that used<
,>
,<=
,>=
,=
,!=
/<>
,IN
, orBETWEEN
yielding false positive or negative results. (Bug #13463415, Bug #11758543, Bug #63502, Bug #50756)An application linked against
libmysqld
could crash in debug mode with astack smashing detected
error if it tried to connect without specifying the user name. (Bug #13460909)Instantiating a derived table for a query with an empty result caused a server crash. (Bug #13457552)
When the optimizer performed conversion of
DECIMAL
values while evaluating range conditions, it could produce incorrect results. (Bug #13453382)Implicitly grouped queries with a
const
table and no matching rows could return incorrect results. (Bug #13430588)For debug builds, enabling
optimizer_trace
could cause an assertion to be raised. (Bug #13430443)Enabling index condition pushdown could cause performance degradation. (Bug #13430436)
When a fixed-width row was inserted into a
MyISAM
temporary table, the entire content of the record buffer was written to the table, including any trailing space contained inVARCHAR
columns, the issue being that this trailing space could be uninitialized. This problem has been resolved by insuring that only the bytes actually used to store theVARCHAR
(and none extra) are copied and inserted in such cases. (Bug #13389854, Bug #79028, Bug #22123583)Fractional seconds parts were lost for certain
UNION ALL
queries. (Bug #13375823)When merging ranges that effectively resulted in a full index scan, the optimizer did not discard the range predicate as unneeded. (Bug #13354910)
When executing
EXPLAIN
, it was assumed that only the default multi-range read implementation could produce an ordered result; this meant that when a query on a table that used a storage engine providing its own sorted MRR, it was ignored, so thatEXPLAIN
failed to reportUsing MRR
even when a multi-range read was used. (Bug #13330645)Some multiple-table updates could update a row twice. (Bug #13095459)
Performance Schema
idle
event timings were not normalized to the same units as wait timings. (Bug #13018537)-
In MySQL 5.6.3, a number of status variables were changed to
longlong
types so that they would roll over much later. However, the format string used by mysqladmin status to printQueries per second
values did not reflect this, causing such values to be misreported. (Bug #12990746)References: See also: Bug #42698. This issue is a regression of: Bug #11751727.
For debug builds, two assertions could be raised erroneously for
UPDATE
statements. (Bug #12912171)-
When the result of a stored function returning a non-integer type was evaluated for
NULL
, an incorrect type warning (Warning 1292 Truncated incorrect INTEGER value) is generated, although such a test for NULL should work with any type. This could cause stored routines not handling the warning correctly to fail.The issue could be worked around by wrapping the result in an expression, using a function such as
CONCAT()
. (Bug #12872824, Bug #62125) When running mysqldump with both the
--single-transaction
and--flush-logs
options, the flushing of the log performed an implicitCOMMIT
(see Statements That Cause an Implicit Commit), causing more than one transaction to be used and thus breaking consistency. (Bug #12809202, Bug #61854)A query that used an aggregate function such as
MAX()
orMIN()
of an index withNOT BETWEEN
in theWHERE
clause could fail to match rows, thus returning an invalid result. (Bug #12773464, Bug #61925)With
ONLY_FULL_GROUP_BY
SQL mode enabled, columns that were not aggregated in the select list or named in aGROUP BY
were incorrectly permitted inORDER BY
. (Bug #12626418)Mishandling of
NO_BACKSLASH_ESCAPES
SQL mode within stored procedures on slave servers could cause replication failures. (Bug #12601974)Passing a user variable as an argument to
GROUP_CONCAT()
could cause a server exit if the variable value changed during query execution. (Bug #12408412)LOAD INDEX INTO CACHE
could cause a server exit if the index cache was too small. (Bug #12361113)With
ONLY_FULL_GROUP_BY
SQL mode enabled, a query that usesGROUP BY
on a column derived from a subquery in theFROM
clause failed with acolumn isn't in GROUP BY
error, if the query was in a view. (Bug #11923239)Attempting to execute
ALTER TABLE
on a temporaryMERGE
table having an underlying temporary table rendered theMERGE
table unusable, unless theALTER TABLE
specified a new list of underlying tables. (Bug #11764786, Bug #57657)It was possible in the event of successive failures for mysqld_safe to restart quickly enough to consume excessive amounts of CPU. Now, on systems that support the sleep and date system utilities, mysqld_safe checks to see whether it has restarted more than 5 times in the current second, and if so, waits 1 second before attempting another restart. (Bug #11761530, Bug #54035)
-
A
HAVING
clause in a query usingMIN()
orMAX()
was sometimes ignored. (Bug #11760517, Bug #52935)References: See also: Bug #11758970, Bug #51242, Bug #11759718, Bug #52051.
When used with the
--xml
option, mysqldump--routines
failed to dump any stored routines, triggers, or events. (Bug #11760384, Bug #52792)-
If an attempt to initiate a statement failed, the issue could not be reported to the client because it was not prepared to receive any error messages prior to the execution of any statement. Since the user could not execute any queries, they were simply disconnected without providing a clear error.
After the fix for this issue, the client is prepared for an error as soon as it attempts to initiate a statement, so that the error can be reported prior to disconnecting the user. (Bug #11755281, Bug #47032)
Previously,
.OLD
files were not included among the files deleted byDROP DATABASE
. Files with this extension are now also deleted by the statement. (Bug #11751736, Bug #42708)A prepared statement using a view whose definition changed between preparation and execution continued to use the old definition, which could cause the prepared statement to return incorrect results. (Bug #11748352, Bug #36002)
Some debugging information was written to the buffer after a flush, resulting in the information not appearing until the next flush. (Bug #64048, Bug #13608112)
Locale information for
FORMAT()
function instances was lost in view definitions. (Bug #63020, Bug #13344643)mysqlhotcopy failed for databases containing views. (Bug #62472, Bug #13006947, Bug #12992993)
The VIO description string was initialized even for connections where it was unneeded. (Bug #62285, Bug #12951586)
On Windows, pasting multiple-line input including a CRLF terminator on the last line into the mysql client resulted in the first character of the last line being changed, resulting in erroneous statements. Handling of newlines in pasted input was also incorrect. (Bug #60901, Bug #12589167, Bug #64104, Bug #13639107)
-
The contents of the
shared
andshared-compat
RPM packages had been changed in versions 5.5.6 and 5.6.1 to avoid the overlap which they traditionally had (and still have in MySQL 5.0 and 5.1). However, the RPM meta information had not been changed in accordance, and so RPM still assumed a conflict betweenshared
andshared-compat
RPM packages. This has been fixed. (Bug #60855, Bug #12368215)References: See also: Bug #56150.
The result of
SUBSTRING_INDEX()
could be missing characters when used as an argument to conversion functions such asLOWER()
. (Bug #60166, Bug #11829861)UPDATE IGNORE
returned an incorrect count for number of rows updated when there were duplicate-key conflicts in a multiple-table update. (Bug #59715, Bug #11766576)The optimizer mishandled
STRAIGHT_JOIN
used with nested joins; for example, by not evaluating tables in the specified order. (Bug #59487, Bug #11766384, Bug #43368, Bug #11752239, Bug #60080, Bug #11766858)A subquery involved in a comparison requiring a character set conversion caused an error that resulted in a server crash. (Bug #59185, Bug #11766143)
The embedded server crashed when
argc = 0
. (Bug #57931, Bug #12561297)If tables were locked by
LOCK TABLES ... READ
in another session,SET GLOBAL read_only = 1
failed to complete. (Bug #57612, Bug #11764747)Invalid memory reads could occur when
cmp_item_sort_string::store_value()
tried to refer to a temporary value that could be changed or deleted by other functions. (Bug #57510, Bug #11764651)Assigning the result of a subquery to a user variable raised an assertion when the outer query included
DISTINCT
andGROUP BY
. (Bug #57196, Bug #11764371)For comparisons containing out-of-range constants, the optimizer permitted warnings to leak through to the client, even though it accounted for the range issue internally. (Bug #56962, Bug #11764155)
A confusing
CREATE TABLE
error message was improved. (Bug #54963, Bug #11762377)The
handle_segfault()
signal-handler code in mysqld could itself crash due to calling unsafe functions. (Bug #54082, Bug #11761576)Using myisamchk with the sort recover method to repair a table having fixed-width row format could cause the row pointer size to be reduced, effectively resulting in a smaller maximum data file size. (Bug #48848, Bug #11756869)
Enabling
myisam_use_mmap
could cause the server to crash. (Bug #48726, Bug #11756764)For
MEMORY
tables, a scan of aHASH
index on aVARCHAR
column could fail to find some rows if the index was on a prefix of the column. (Bug #47704, Bug #11755870)myisam_sort_buffer_size
could not be set larger than 4GB on 64-bit systems. (Bug #45702, Bug #11754145)-
The stored routine cache was subject to a small memory leak that over time or with many routines being used could result in out-of-memory errors.
The fix for this issue also introduces a new global server system variable
stored_program_cache
which can be used for controlling the size of the stored routine cache. (Bug #44585, Bug #11753187) Under some circumstances, the result of
SUBSTRING_INDEX()
incorrectly depended on the contents of the previous row. (Bug #42404, Bug #11751514)Setting an event to
DISABLED
status and with theON COMPLETION NOT PRESERVE
attribute caused it to be dropped at the next server restart. (Bug #37666, Bug #11748899)Due to improper locking, concurrent inserts into an
ARCHIVE
table at the same time as repair and check operations on the table resulted in table corruption. (Bug #37280, Bug #11748748)Stored functions could produce an error message that referred to
ORDER BY
even though the offending statement within the function had no such clause. (Bug #35410, Bug #11748187)