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MySQL 5.6 Release Notes  /  Changes in MySQL 5.6.9 (2012-12-11, Release Candidate)

Changes in MySQL 5.6.9 (2012-12-11, Release Candidate)

Deprecation and Removal Notes

  • Microsoft Windows: Windows Vista, Windows Server 2008, and newer support native symbolic linking using the mklink command. This makes the MySQL Server implementation of database symbolic links using .sym files redundant, so that mechanism is now deprecated and will be removed in a future MySQL release. See Using Symbolic Links for Databases on Windows.

Installation Notes

  • The --random-passwords option for mysql_install_db is now supported for MySQL install operations (not upgrades) using Solaris PKG packages.

Functionality Added or Changed

  • Incompatible Change; Replication: A number of variable and other names relating to GTID-based replication have been changed, with a view to making these names more appropriate and meaningful. The old names are no longer supported.

    The features so renamed are shown in the following list:

    For more information, see Replication with Global Transaction Identifiers, and Global Transaction ID Options and Variables. (Bug #14775984)

  • For client connections restrictd by the server because the client account password is expired, the server now permits SET PASSWORD only if the account named in the statement matches the account used by the client. (Bug #14807074)

    References: See also: Bug #14698309.

  • The server now provides thread information (for SHOW PROCESSLIST) to indicate the progress of in-place ALTER TABLE operations:

    • preparing for alter table

      The server is preparing to execute an in-place ALTER TABLE.

    • altering table

      The server is in the process of executing an in-place ALTER TABLE.

    • committing alter table to storage engine

      The server has finished an in-place ALTER TABLE and is committing the result.

    (Bug #14790408)

  • InnoDB automatically extends each secondary index by appending the primary key columns to it. Previously, the optimizer did not take into account the primary key columns of the extended secondary index when determining how and whether to use that index. Now the optimizer takes the primary key columns into account, which can result in more efficient query execution plans and better performance.

    The optimizer can use extended secondary keys for ref, range, and index_merge index access, for Loose Index Scan, for join and sorting optimization, and for MIN()/MAX() optimization.

    The new use_index_extensions flag of the optimizer_switch system variable permits control over whether the optimizer takes the primary key columns into account when determining how to use an InnoDB table's secondary indexes. By default, use_index_extensions is enabled. To check whether disabling use of index extensions will improve performance, use this statement:

    SET optimizer_switch = 'use_index_extensions=off';

    For more information, see Use of Index Extensions. (Bug #62025, Bug #12814559, Bug #56714, Bug #11763940)

  • mysqld now writes dates to the error log in ISO (YYYY-MM-DD hh:mm:ss) format. It also includes its process ID following the date. Thanks to Davi Arnaut for the patch. (Bug #56240, Bug #11763523)

Bugs Fixed

  • Incompatible Change: The THREAD_ID column in Performance Schema tables was widened from INT to BIGINT to accommodate 64-bit values.


    As a consequence of this change, the PROCESSLIST_ID column of the threads table is now NULL for background threads. Previously, the value was 0 for background threads.

    If you upgrade to this MySQL release from an earlier version, you must run mysql_upgrade (and restart the server) to incorporate this change to the performance_schema database. (Bug #14664453)

  • Incompatible Change: LAST_INSERT_ID(expr) did not work for expr values greater than the largest signed BIGINT value. Such arguments now are accepted, with some consequences for compatibility with previous versions:

    • LAST_INSERT_ID() now returns a BIGINT UNSIGNED value, not a BIGINT (signed) value.

    • LAST_INSERT_ID(expr) now returns an unsigned integer value, not a signed integer value.

    • For AUTO_INCREMENT columns, negative values are no longer supported.

    (Bug #20964, Bug #11745891)

  • Incompatible Change: Connection ID (thread ID) values greater than 32 bits can occur on some systems (such as busy or long-running 64-bit systems), causing these problems:

    • Connection IDs written to the general query log and slow query log were incorrect. This was true for logging to both files and tables.

    • The CONNECTION_ID() function could return a value with a data type too small for values larger than 32 bits.

    • The mysql_thread_id() and mysql_kill() C API functions did not handle ID values larger than 32 bits. This could result in killing the wrong thread; for example, if you invoked mysql_kill(mysql_thread_id()).

    Connection IDs now are permitted to be 64-bit values when the server supports them (when built with 64-bit data types), which has these effects:

    • Connection IDs are logged correctly to the general query log and slow query log.


      This change involves a modification to the log tables, so after upgrading to this release, you must run mysql_upgrade and restart the server.

    • CONNECTION_ID() returns a data type appropriate for values larger than 32 bits.

    • mysql_thread_id() is unchanged; the client/server protocal has only 4 bytes for the ID value. This function returns an incorrect (truncated) value for connection IDs larger than 32 bits and should be avoided.

      mysql_kill() still cannot handle values larger than 32 bits, but to guard against killing the wrong thread now returns an error in these cases:

      To avoid problems with mysql_thread_id() and mysql_kill(), do not use them. To get the connection ID, execute a SELECT CONNECTION_ID() query and retrieve the result. To kill a thread, execute a KILL statement.

    (Bug #19806, Bug #11745768, Bug #65715, Bug #14236124, Bug #44728, Bug #11753308)

  • Important Change; InnoDB: A DML statement using the index merge access method could lock many rows from the table, even when those rows were not part of the final result set. This fix reduces the excessive locking by releasing the locks of unmatched rows. This optimization affects only transactions with isolation level equal to or less strict than READ COMMITTED; it does not apply to transactions using REPEATABLE READ or SERIALIZABLE isolation level. (Bug #14226171)

  • Important Change; Replication: Statements involving the Performance Schema tables should not be written to the binary log, because the content of these tables is applicable only to a given MySQL Server instance, and may differ greatly between different servers in a replication topology. The database administrator should be able to configure (INSERT, UPDATE, or DELETE) or flush (TRUNCATE TABLE) performance schema tables on a single server without affecting others. However, when using replication with GTIDs enabled (see Replication with Global Transaction Identifiers), warnings about unsafe statements updating Performance Schema tables were elevated to errors, preventing the use of performance_schema and GTIDs together.

    Similar problems were encountered with replication and system logging tables when GTIDs were enabled.

    This fix introduces the concept of a nonreplicated or local table. Now when MySQL replication encounters a table that is marked as local, updates to this table are ignored.

    This fix defines as local the following tables, which are no longer replicated:

    • All tables in the performance_schema database

    • mysql.general_log

    • mysql.slow_log

    • mysql.slave_relay_log_info

    • mysql.slave_master_info

    • mysql.slave_worker_info

    Before this fix, statements using the performance_schema and other tables just listed were handled by being marked as unsafe for replication, which caused warnings during execution; the statements were nonetheless written to the binary log, regardless of the logging format in effect.

    Existing replication behavior for tables in the INFORMATION_SCHEMA database is not changed by this fix.

    For more information, see MySQL Performance Schema. See also MySQL Server Logs, and Replication Metadata Repositories. For information about general and slow query log tables, see Selecting General Query Log and Slow Query Log Output Destinations. (Bug #14741537)

  • Important Change; Replication: Because running the server with GTIDs enabled prevented changes to nontransactional tables, programs such as mysql_upgrade and mysql_install_db were unable to operate on system tables that used the MyISAM storage engine and therefore could not function correctly. Now, when running with --enforce-gtid-consistency (required whenever --gtid-mode=ON), the server allows single statements on nontransactional tables. (Bug #14722659)

  • Important Change; Replication: Formerly, the value of the Seconds_Behind_Master column in the output of SHOW SLAVE STATUS was always set to NULL whenever the SQL thread or the I/O thread was stopped. Now, this column is set to NULL only if the SQL thread is not running, or if the I/O thread is not running following a check to determine whether or not the SQL thread has processed all of the relay log. (If the SQL thread has finished processing and the I/O thread is running, Seconds_Behind_Master is 0.) (Bug #12946333)

  • Performance; InnoDB: The timing values for low-level InnoDB read operations were adjusted for better performance with fast storage devices, such as SSD. This enhancement primarily affects read operations for BLOB columns in compressed tables. (Bug #13702112, Bug #64258)

  • InnoDB; Partitioning: Previously, when attempting to optimize one or more partitions of a partitioned table that used a storage engine that does not support partition-level OPTIMIZE, such as InnoDB, MySQL reported Table does not support optimize, doing recreate + analyze instead, then re-created the entire table, but did not actually analyze it. Now in such cases, the warning message is, Table does not support optimize on partitions. All partitions will be rebuilt and analyzed. In addition, the entire table is analyzed after first being rebuilt. (Bug #11751825, Bug #42822)

  • InnoDB: The server could halt with an error when two kinds of operations happened simultaneously:

    • A ROLLBACK of an inserted row that contained off-page columns.

    • An online DDL operation involving a table of ROW_FORMAT=DYNAMIC or ROW_FORMAT=COMPRESSED (that is, using the Barracuda file format) that rebuilt the table. For example, ADD/DROP COLUMN, ADD PRIMARY KEY, change ROW_FORMAT.

    (Bug #14842014)

  • InnoDB: If the server crashed while rows were inserted into a table with a FULLTEXT index but before the transaction was committed, an error could occur during the next startup:

    InnoDB: Assertion failure in thread thread_num in file line 1019

    (Bug #14826779)

  • InnoDB: The server could halt with an error when accessing an InnoDB table containing a FULLTEXT index through the HANDLER statement. (Bug #14788710)

  • InnoDB: A timeout error could occur on Windows systems when doing ALTER TABLE statements with the DISCARD TABLESPACE or IMPORT TABLESPACE clauses, due to a temporary tablespace file remaining in the file system. (Bug #14776799)

  • InnoDB: InnoDB tables with FULLTEXT indexes could allocate memory for thread handles that was never released, possibly leading to resource issues on Windows systems. (Bug #14759163)

  • InnoDB: The server could halt with an assertion error for an ANALYZE TABLE operation, depending on the structure of the table and its indexes:

    InnoDB: Assertion failure in thread thread_num in file dict0dict.ic line 447
    InnoDB: Failing assertion: pos < table->n_def

    (Bug #14755452)

  • InnoDB: During an online DDL operation that copies the table, the secondary index of the table could become corrupted. (Bug #14753701)

  • InnoDB: An online DDL operation for an InnoDB table incorrectly reported an empty value ('') instead of the correct key value when it reported a duplicate key error for a unique index using an index prefix. (Bug #14729221)

  • InnoDB: If the server crashed after an online DDL CREATE INDEX operation, an error could occur while rolling back incomplete transactions on the next startup:

    InnoDB: error in sec index entry del undo in
    InnoDB: Assertion failure in thread thread_num in file line 559

    (Bug #14707452)

  • InnoDB: This fix improves the error handling when an ALTER TABLE operation adds a column beyond the maximum number allowed for an InnoDB table. It also raises the maximum number of columns for an InnoDB table from 1000 to 1020. (Bug #14705287)

  • InnoDB: This fix makes MySQL more responsive to KILL QUERY statements when the query is accessing an InnoDB table. (Bug #14704286)

  • InnoDB: If the server crashed at a precise moment during an ALTER TABLE operation that rebuilt the clustered index for an InnoDB table, the original table could be inaccessible afterward. An example of such an operation is ALTER TABLE ... ADD PRIMARY KEY The fix preserves the original table if the server halts during this operation. You might still need to rename the .ibd file manually to restore the original table contents: in MySQL 5.6 and higher, rename from #sql-ib$new_table_id.ibd to table_name.ibd within the database directory; prior to MySQL 5.6, the temporary file to rename is table_name#1 or #2. (Bug #14669848)

  • InnoDB: During an online DDL operation that rebuilt the table, a CHECK TABLE statement could report a count mismatch for all secondary indexes. (Bug #14606472)

  • InnoDB: After a FULLTEXT index was created and dropped from an InnoDB table, further ALTER TABLE operations to add, drop, and rename columns could cause a serious error. Regression of bug #13972248. (Bug #14504337)

  • InnoDB: If an ALTER TABLE statement failed while attempting to create a FULLTEXT index for an InnoDB table, the server could halt with an assertion error while dropping the incomplete index. (Bug #14504174)

  • InnoDB: During shutdown, with the innodb_purge_threads configuration option set greater than 1, the server could halt prematurely with this error:

    mysqld got signal 11

    A workaround was to increase innodb_log_file_size and set innodb_purge_threads=1. The fix was backported to MySQL 5.5 and 5.1, although those versions do not have the innodb_purge_threads configuration option so the error was unlikely to occur. (Bug #14234028)

  • InnoDB: The server could halt with an error under some combinations of concurrent operations:

    InnoDB: unknown error code 20

    This issue originated during the 5.6 development cycle. It affected only transactions using the READ COMMITTED andREAD UNCOMMITTED isolation levels. (Bug #13641662, Bug #12424846)

  • InnoDB: This fix improves the error message when a foreign key constraint cannot be created. Instead of referring to an inability to create a table with an auto-generated name, the message clearly states the error:

    ERROR 1215 (HY000): Cannot add foreign key constraint

    Issuing a subsequent SHOW WARNINGS statement provides additional detail about any secondary indexes that are required. (Bug #11745444, Bug #15324)

  • Replication: If a table to be replicated had a FULLTEXT index, this index was not ruled out when selecting the type of scan to be used in finding the next row, even though it cannot be used to find the correct one. The row applier subsequently tried unsuccessfully to employ an index scan, causing replication to fail. Now in such cases, indexes which do not provide for sequential access (such as FULLTEXT) are not considered when determining whether to use a table, index, or hash scan for this purpose. (Bug #14843764)

  • Replication: Given a stored routine R in which the GTID_SUBTRACT() function was invoked: Once GTID_SUBTRACT() returned NULL when called inside R, it continued to return NULL every time it was called within R, for the remainder of the client session. (Bug #14838575)

  • Replication: When using the GTID-aware master-slave protocol, the slave I/O thread used the wrong position. When using GTIDs, the position is not normally used, but as a special case, the position was used in addition to the GTID when the slave reconnected to the same master (even though this was not necessary). This problem is fixed by making the GTID-aware master-slave protocol not use positions at all any longer. (Bug #14828028)

  • Replication: MySQL Enterprise Backup, mysqldump, and mysqlhotcopy could not be used with a GTID-enabled MySQL Server, because they were unable to restore the server's GTID state and so could not restore from any point in the binary log other than the very beginning.

    As part of the fix for this problem, the gtid_purged system variable (formerly named gtid_lost) is no longer read-only; now it is possible to add GTIDs to it when gtid_executed (formerly gtid_done) is empty. (Bug #14787808)

  • Replication: Restarting replication after the first binary log file was purged resulted in the error Got fatal error 1236 from master when reading data from binary log: 'The slave is connecting using CHANGE MASTER TO MASTER_AUTO_POSITION = 1, but the master has purged binary logs containing GTIDs that the slave requires.' This led GTID-based replication to fail. (Bug #14756691)

  • Solaris: Installation using Solaris packages ran mysql_install_db during upgrade operations (this should occur only for new installations). (Bug #14747671, Bug #16534721)

  • mysql_install_db failed to honor the --user option. (Bug #15866735)

  • The optimizer could allocate insufficient memory when determining subquery execution strategies, causing the server to exit. (Bug #14846866)

  • The optimizer could raise an assertion when evaluating a range test against an IS NOT NULL condition. (Bug #14843705)

  • init_io_cache() used memset() to clear a mutex but passed the wrong mutex size. (Bug #14838882)

  • Creating an InnoDB table with a FULLTEXT index could encounter a serious error if the table name contained nonalphanumeric characters. (Bug #14835178, Bug #16036699)

  • Out-of-bounds reads could occur within filename_to_tablename(). (Bug #14834378)

  • When a backup is taken using mysqldump on a server with global transaction IDs (GTIDs) enabled, the dump file did not contain any GTID information. This eventually results in replicating the transactions from the beginning of history when the backup is used to bring up a slave.

    To enable control over GTID information written to the dump file, mysqldump now has a --set-gtid-purged option that indicates whether to add a SET @@GLOBAL.gtid_purged statement to the output.

    The following table shows the permitted option values. The default value is AUTO.

    Value Meaning
    OFF Add no SET statement to the output.
    ON Add a SET statement to the output. An error occurs if GTIDs are not enabled on the server.
    AUTO Add a SET statement to the output if GTIDs are enabled on the server.

    (Bug #14832472)

  • With LOCK TABLES in effect, CREATE TABLE IF NOT EXISTS ... LIKE could raise an assertion. (Bug #14788976)

  • An assertion could be raised executing INSERT, UPDATE, or DELETE after implicitly starting a READ ONLY transaction in LOCK TABLES mode. (Bug #14788540)

  • A query with a union and a join could crash the parser. (Bug #14786792, Bug #16076289)

  • Attempting to read a utf16 file with LOAD DATA raised an assertion. (Bug #14786470)

  • The automatic key generation part of derived table handling did not handle properly columns specified as part of the VALUES() clause and caused an assertion to be raised. (Bug #14786324)

  • Invalid memory reads could occur for queries that selected from a zero-length table name. (Bug #14780820)

  • SHOW PROCESSLIST output was not sorted in Id order. (Bug #14771006)

  • For some SELECT statements, EXPLAIN could cause the server to exit. (Bug #14761894)

  • Attempting to create an auto-increment column in an InnoDB table with a NULL type attribute could cause a serious error. (Bug #14758479)

  • A memory leak occurred for attempts to use ALTER TABLE to set a default value for a tiny, medium, or long BLOB or TEXT column. (Bug #14756206)

  • An assertion was raised if ALTER TABLE was used to rename a column to same name as an existing column while also reordering the renamed column using AFTER or FIRST. (Bug #14756089)

  • An assertion could be raised if semijoin materialization was used to evaluate a NOT IN subquery. (Bug #14751858)

  • After issuing ALTER TABLE ... DISCARD TABLESPACE, an online DDL operation for the same table could fail on Windows systems with an error: Got error 11 from storage engine. An ALTER TABLE statement with the ALGORITHM=INPLACE clause could also create an empty .ibd file, making the tablespace no longer discarded. (Bug #14735917)

  • For some continuation handler nestings, continuation could occur at the wrong location. (Bug #14724836)

  • Starting the server with bind_address and then setting host_cache_size to 0 could result in the server stopping for certain kinds of client connections. (Bug #14689561)

  • For UPDATE statements, EXPLAIN showed the total key length in the key_len column rather than the length of the used key parts. (Bug #14682438)

  • With index condition pushdown enabled, the optimizer could produce incorrect results for derived tables. (Bug #14640176)

  • SHOW PROFILE could be used to cause excessive server memory consumption. (Bug #14629232)

  • The optimizer could incorrectly use a nonspatial index to optimize spatial operations, causing an assertion to be raised. (Bug #14600994)

  • Several problems with mysql_config_editor were fixed:

    • There was no error message for write errors to the configuration file.

    • The --all option is not supported for the remove command, but there was no warning message for attempts to use remove --all.

    • The --all option is not supported for the set command, but there was no warning message for attempts to use set --all.

    In addition, the --user, --password, and --host options now are supported for the remove command. When present, the remove command removes only the requested values from the login path. If none of them is given, remove removes the entire client login path. For example, this command removes only the user value from the client login path rather than the entire client login path:

    mysql_config_editor remove --login-path=client --user

    (Bug #14505672, Bug #14545989, Bug #14545999)

  • A LIKE pattern with too many '%' wildcards could cause a segmentation fault. (Bug #14303860)

  • Previously, the events_statements_summary_by_digest Performance Schema table was a summary grouped by the DIGEST column alone. Now this table contains a SCHEMA_NAME column and the digest summary is grouped by the SCHEMA_NAME and DIGEST columns.

    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. (Bug #14075527)

  • Query rewriting to scrub passwords for logging was done even if none of the associated logs were enabled. Also, CREATE SERVER and ALTER SERVER are now rewritten as necessary. (Bug #14073554)

  • CREATE TABLE ... SELECT could create a table with a column of type NULL, which when accessed caused a server exit. (Bug #14021323, Bug #23280699)

  • CHECK TABLE and REPAIR TABLE could crash if a MyISAM table had a corrupt key (.MYI) file. Now the server produces an error. (Bug #13556441)

  • CHECK TABLE and REPAIR TABLE could crash if a MyISAM table had a corrupt key (.MYI) file. Now the server produces an error. (Bug #13556107, Bug #13556000)

  • A buffer too small error message from the myisamchk command referred to the myisam_sort_buffer_size configuration option, when it should have referred to sort_buffer_size.

    myisamchk now has a myisam_sort_buffer_size variable available as an alternative name to sort_buffer_size. myisam_sort_buffer_size is preferable to sort_buffer_size because its name corresponds to the myisam_sort_buffer_size server system variable that has a similar meaning. sort_buffer_size should be considered deprecated. (Bug #11754894, Bug #46578)

  • The host_cache Performance Schema table displayed some lines multiple times. This was not an issue with the host cache itself, only with the table that provides information about the cache contents. (Bug #67236, Bug #14764890)

  • On OS X, reinitializing the query cache could cause the server to exit. Thanks to Davi Arnaut for the patch. (Bug #67156, Bug #14741880)

  • The server failed to use the query cache for queries in which a database or table name contained special characters and the table storage engine was InnoDB. (Bug #64821, Bug #13919851)

  • mysqld_safe ignored the value of the UMASK environment variable, leading to behavior different from mysqld with respect to the access mode of created files. Now mysqld_safe (and mysqld_multi) attempt to approximate the same behavior as mysqld. (Bug #57406, Bug #11764559)

  • For dumps of the mysql database, mysqldump skipped the event table unless the --events option was given. This no longer occurs. To skip the event table if that is desired, use the --ignore-table option instead (Bug #55587, Bug #11762933)

  • For MEMORY tables with HASH indexes, DELETE sometimes failed to delete all applicable rows. (Bug #51763, Bug #11759445)

  • On OS X, KILL could sometimes be unreliable. (Bug #37780, Bug #11748945)