MySQL Community Edition is a freely downloadable version of the world's most popular open source database that is supported by an active community of open source developers and enthusiasts.
MySQL delivers enterprise features, including:
- Partitioning to improve performance and management of very large database environments
- Row-based/Hybrid Replication for improved replication security
- Event Scheduler to create and schedule jobs that perform various database tasks
- XPath Support
- Dynamic General/Slow Query Log
- Performance/Load Testing Utility (mysqlslap)
- Improved! Full Text Search (faster, new dev templates)
- Improved! Archive engine (better compression, more features)
- Improved! User session and problem SQL identification
- Improved! MySQL embedded library (libmysqld)
- Additional INFORMATION_SCHEMA objects
- Faster data import operations (parallel file load)
- ACID Transactions to build reliable and secure business critical applications
- Stored Procedures to improve developer productivity
- Triggers to enforce complex business rules at the database level
- Views to ensure sensitive information is not compromised
- Information Schema to provide easy access to metadata
- Pluggable Storage Engine Architecture for maximum flexibility
- Archive Storage Engine for historical and audit data
# Functionality Added or Changed
- Replication: The functions GTID_SUBTRACT() and GTID_SUBSET() were formerly available in libmysqld only when it was built with replication support. Now these functions are always available when using this library, regardless of how it was built.
- MySQL no longer uses the default OpenSSL compression.
- There is now a distinct error code (ER_MUST_CHANGE_PASSWORD_LOGIN) for the error sent by the server to a client authenticating with an expired password.
- mysql_config_editor now supports --port and --socket options for specifying TCP/IP port number and Unix socket file name.
- mysqlcheck has a new --skip-database option. The option value is the name of a database (case sensitive) for which checks should be skipped.
- mysql_upgrade uses this option to upgrade the system tables in the mysql database before tables in other databases: It upgrade the mysql database, then all databases except the mysql database. This avoids problems that can occur if user tables are upgraded before the system tables.
- The only supported value for the innodb_mirrored_log_groups system variable is 1, so this variable is now deprecated. Setting it to 1 at startup results in a warning. Setting it to a value other than 1 at startup results in an error and the server exits. This variable will be removed in a future release.
# Bugs Fixed
- Performance; InnoDB: Switching the MySQL table used by the InnoDB memcached interface (using the @@ notation), was made more efficient, by reading cached information about the cache policy to use for each table. This optimization lets you frequently switch between tables during a session that uses the memcached interface, without incurring I/O overhead from examining table metadata each time.
- Performance; InnoDB: Performance was improved for operations on tables with many rows that were deleted but not yet purged. The speedup applies mainly to workloads that perform bulk deletes, or updates to the primary key columns, and where the system is busy enough to experience purge lag.
- Performance; InnoDB: The DROP TABLE statement for a table using compression could be slower than necessary, causing a stall for several seconds. MySQL was unnecessarily decompressing pages in the buffer pool related to the table as part of the DROP operation.
- Performance; InnoDB: The I/O routines used when the AIO subsystem were made more efficient, to merge consecutive I/O requests into a single operation. This fix solves a performance issue introduced during the 5.6 development cycle.
- Incompatible Change; Partitioning: Changes in the KEY partitioning hashing functions used with numeric, date and time, ENUM, and SET columns in MySQL 5.5 makes tables using partitioning or subpartitioning by KEY on any of the affected column types and created on a MySQL 5.5 or later server incompatible with a MySQL 5.1 server. This is because the partition IDs as calculated by a MySQL 5.5 or later server almost certainly differ from those calculated by a MySQL 5.1 server for the same table definition and data as a result of the changes in these functions.
- The principal changes in the KEY partitioning implementation in MySQL 5.5 resulting in this issue were as follows: 1. The hash function used for numeric and date and time columns changed from binary to character-based. 2. The base used for hashing of ENUM and SET columns changed from latin1 ci characters to binary.
- The fix involves adding the capability in MySQL 5.5 and later to choose which type of hashing to use for KEY partitioning, which is implemented with a new ALGORITHM extension to the PARTITION BY KEY option for CREATE TABLE and ALTER TABLE. Specifying PARTITION BY KEY ALGORITHM=1 ([columns]) causes the server to use the hashing functions as implemented in MySQL 5.1; using ALGORITHM=2 causes the server to use the hashing functions from MySQL 5.5 and later. ALGORITHM=2 is the default. Using the appropriate value for ALGORITHM, you can perform any of the following tasks:
> Create KEY partitioned tables in MySQL 5.5 and later that are compatible with MySQL 5.1, using CREATE TABLE ... PARTITION BY KEY ALGORITHM=1 (...).
> Downgrade KEY partitioned tables that were created in MySQL 5.5 or later to become compatible with MySQL 5.1, using ALTER TABLE ... PARTITION BY KEY ALGORITHM=1 (...).
> Upgrade KEY partitioned tables originally created in MySQL 5.1 to use hashing as in MySQL 5.5 and later, using ALTER TABLE ... PARTITION BY KEY ALGORITHM=2 (...).
- Important Change; Replication: Executing a statement that performs an implicit commit but whose changes are not logged when gtid_next is set to any value other than AUTOMATIC is not permitted. Now in such cases, the statement fails with an error. This includes the statements in the following list:
> CHANGE MASTER TO
> START SLAVE
> STOP SLAVE
> REPAIR TABLE
> OPTIMIZE TABLE
> ANALYZE TABLE
> CHECK TABLE
> CREATE SERVER
> ALTER SERVER
> DROP SERVER
> CACHE INDEX
> LOAD INDEX INTO CACHE
- Important Change; Replication: The version number reported by mysqlbinlog --version has been increased to 3.4.
- Important Note; Replication: It was possible to replicate from a table to a same-named view using statement-based logging, while using row-based logging instead led to a failure on the slave. Now the target object type is checked prior to performing any DML, and an error is given if the target on the slave is not actually a table. This is true regardless of the binary logging format in use.
- InnoDB: When ADD PRIMARY KEY columns are reordered in an ALTER TABLE statement (for example: ALTER TABLE t1 ADD PRIMARY KEY(a,b), CHANGE a a INT AFTER b), the log apply for UPDATE operations would fail to find rows.
- InnoDB: ALTER TABLE operations on InnoDB tables that added a PRIMARY KEY using a column prefix could produce an incorrect result.
- InnoDB: For ALTER TABLE operations on InnoDB tables that required a table-copying operation, other transactions on the table might fail during the copy. However, if such a transaction issued a partial rollback, the rollback was treated as a full rollback.
- InnoDB: When parsing a delimited search string such as “abc-def” in a full-text search, InnoDB now uses the same word delimiters as MyISAM.
- InnoDB: This fix improves code readability by addressing naming inconsistencies for InnoDB PERFORMANCE_SCHEMA key declarations.
- InnoDB: This fix disables a condition for extra splitting of clustered index leaf pages, on compressed tables. Extra page splitting was only done to reserve space for future updates, so that future page splits could be avoided.
- InnoDB: For InnoDB tables, if a PRIMARY KEY on a VARCHAR column (or prefix) was empty, index page compression could fail.
- InnoDB: Status values in the INNODB_FT_CONFIG table would not update. The INNODB_FT_CONFIG is intended for internal configuration and should not be used for statistical information purposes. To avoid confusion, column values that are intended for internal use have been removed from the INNODB_FT_CONFIG table. This fix also removes the INNODB_FT_INSERTED table and other internal full text search-related tables that were unintentionally exposed.
- InnoDB: With innodb_api_enable_mdl=OFF, an ALTER TABLE operation on an InnoDB table that required a table copy could cause a server exit.
- InnoDB: Improper testing of compatibility between the referencing and referenced during ALTER TABLE ... ADD FOREIGN key could cause a server exit.
- InnoDB: Rollback did not include changes made to temporary tables by read-only transactions.
- InnoDB: The InnoDB page-splitting algorithm could recurse excessivly.
- InnoDB: For debug builds, InnoDB status exporting was subject to a race condition that could cause a server exit.
- InnoDB: When using ALTER TABLE to set an AUTO_INCREMENT column value to a user-specified value, InnoDB would set the AUTO_INCREMENT value to the user-specified value even when the AUTO_INCREMENT value is greater than the user-specified value. This fix ensures that the AUTO_INCREMENT value is set to the maximum of the user-specified value and MAX(auto_increment_column)+1, which is the expected behaviour.
- InnoDB: Importing a tablespace with the configuration file present would not import the data file. This problem would occur when all pages are not flushed from the buffer pool after a table is altered using the copy and rename approach. This fix ensures that all pages are flushed from the buffer pool when a table is altered using the copy and rename approach.
- InnoDB: RENAME TABLE would result in a hang due to a MySQL mutex acquisition deadlock.
- InnoDB: Internal read operations could be misclassified as synchronous when they were actually asynchronous. When the I/O requests returned sooner than expected, threads could be scheduled inefficiently. This issue mainly affected read-ahead requests, and thus had relatively little impact on I/O performed by user queries.
- InnoDB: The lock_validate function, which is only present in debug builds, acquired and released mutexes to avoid hogging them. This behavior introduced a window wherein changes to the hash table could occur while code traversed the same set of data. This fix updates lock_validate logic to collect all records for which locks must be validated, releases mutexes, and runs a loop to validate record locks.
- InnoDB: ALTER TABLE functions would perform a check to see if InnoDB is in read-only mode (srv_read_only_mode=true). If InnoDB was in read-only mode, the check would return a successful status and do nothing else. This fix replaces srv_read_only_mode check conditions with debug assertions.
- InnoDB: An improper call to abort() by InnoDB could result in a server exit.
- InnoDB: When the InnoDB buffer pool is almost filled with 4KB compressed pages, inserting into 16KB compact tables would cause 8KB pages_free to increase, which could potentially slow or stall inserts.
- InnoDB: An assertion failure would occur in heap->magic_n == MEM_BLOCK_MAGIC_N due to a race condition that appeared when row_merge_read_clustered_index() returned an error.
- InnoDB: This fix removes an unnecessary debug assertion related to page_hash locks which only affects debug builds. The debug assertion is no longer valid and should have been removed when hash_lock array was introduced in MySQL 5.6.
- InnoDB: The InnoDB memcached plugin could encounter a serious error under a heavy load, such as produced by benchmark runs.
- InnoDB: If the MySQL server halted at a precise moment when a purge operation was being applied from the change buffer, the operation could be incorrectly performed again during the next restart. A workaround was to set the configuration option innodb_change_buffering=changes, to turn off change buffering for purge operations.
- InnoDB: When InnoDB locking code was revised, a call to register lock waits was inadvertently removed. This fix adds the call back to the InnoDB locking code.
- InnoDB: A direct call to the trx_start_if_not_started_xa_low() function would cause a debug assertion.
- InnoDB: In the case of LOCK WAIT for an insert in a foreign key table, InnoDB could report a false dictionary-changed error and cause the insert to fail rather than being retried.
- InnoDB: In some cases, deadlock detection did not work, resulting in sessions hanging waiting for a lock-wait timeout.
- InnoDB: An in-place ALTER TABLE on an InnoDB table could fail to delete the statistics for the old primary key from the mysql.innodb_index_stats table.
- InnoDB: This fix updates InnoDB code in ha_innodb.cc and handler0alter.cc to use TABLE::key_info instead of both TABLE::key_info and TABLE_SHARE::key_info.
- InnoDB: Arithmetic underflow during page compression for CREATE TABLE on an InnoDB table could cause a server exit.
- InnoDB: For debug builds, online ALTER TABLE operations for InnoDB tables could cause a server exit during table rebuilding.
- InnoDB: In some cases, the InnoDB purge coordinator did not use all available purge threads, resulting in suboptimal purge activity.
- InnoDB: On systems that cannot handle unaligned memory access, depending on the stack frame alignment, a SIGBUS error could occur during startup. This issue was observed on Solaris 64-bit systems.
- InnoDB: ALTER TABLE for InnoDB tables was not fully atomic.
- InnoDB: When innodb_mirrored_log_groups was set to a value other than the default 1, the MySQL server encountered a serious error during startup while loading the InnoDB memcached plugin. In earlier releases, the server would refuse to start (but not display an error) when this setting was changed. This fix cleans up the error handling for unsupported values of this configuration option.
- InnoDB: An error at the filesystem level, such as too many open files, could cause an unhandled error during an ALTER TABLE operation. The error could be accompanied by Valgrind warnings, and by this assertion message:
>Assertion `! is_set()' failed.
mysqld got signal 6 ;
- InnoDB: The INNODB_SYNC_ARRAY_SIZE variable was incorrectly allowed to be configured at runtime. As documented, INNODB_SYNC_ARRAY_SIZE must be configured when the MySQL instance is starting up, and cannot be changed afterward. This fix changes INNODB_SYNC_ARRAY_SIZE to a non-dynamic variable, as intended.
- InnoDB: The server could exit during an attempt by InnoDB to reorganize or compress a compressed secondary index page.
- InnoDB: A RENAME TABLE statement could stall for several minutes before timing out. This issue could occurred for a table using compression, with change buffering enabled.
- InnoDB: A DML operation performed while a RENAME TABLE operation waits for pending I/O operations on the tablespace to complete would result in a deadlock.
- InnoDB: If the server was started with the skip-innodb option, or InnoDB otherwise failed to start, query any of these Information Schema tables would cause a severe error:
- InnoDB: Online DDL had a restriction that prevented renaming a column and adding a foreign key involving that column in a single ALTER TABLE statement. Now, this combination of operations is allowed in a single statement.
- InnoDB: When printing out long semaphore wait diagnostics, sync_array_cell_print() ran into a segmentation violation (SEGV) caused by a race condition. This fix addresses the race condition by allowing the cell to be freed while it is being printed.
- InnoDB: The value of the innodb_version variable was not updated consistently for all server releases for the InnoDB Plugin in MySQL 5.1, and the integrated InnoDB component in MySQL 5.5, 5.6, and higher. Since InnoDB and MySQL Server development cycles are fully integrated and synchronized, now the value returned by the innodb_version variable is the same as for the version variable.
- InnoDB: Killing a query caused an InnoDB assertion failure when the same table (cursor) instance was used again. This is the result of a regression error introduced . The fix introduced a check to handle kill signals for long running queries but the cursor was not restored to the proper state.
- InnoDB: On startup, InnoDB reported a message on 64-bit Linux and 64-bit Windows systems stating that the CPU does not support crc32 instructions. On Windows, InnoDB does not use crc32 instructions even if supported by the CPU. This fix revises the wording of the message and implements a check for availability of crc32 instructions.
- InnoDB: The length of internally generated foreign key names was not checked. If internally generated foreign key names were over the 64 character limit, this resulted in invalid DDL from SHOW CREATE TABLE. This fix checks the length of internally generated foreign key names and reports an error message if the limit is exceeded.
- InnoDB: This fix removes left-over prototype code for srv_parse_log_group_home_dirs, and related header comments.
- InnoDB: Attempting to replace the default InnoDB FTS stopword list by creating an InnoDB table with the same structure as INFORMATION_SCHEMA.innodb_ft_default_stopword would result in an error. SHOW CREATE TABLE revealed that the new InnoDB table was created with CHARSET=utf8. The InnoDB FTS stopword table validity check only supported latin1. This fix extends the validity check for all supported character sets.
- Partitioning: ALGORITHM = INPLACE, which was disallowed in MySQL 5.6.10 for DDL statements operating on partitioned tables, can once again be used with such statements.
- Partitioning: A query on a table partitioned by range and using TO_DAYS() as a partitioing function always included the first partition of the table when pruning. This happened regardless of the range employed in the BETWEEN clause of such a query.
- Partitioning: Execution of ALTER TABLE ... DROP PARTITION against a view caused the server to crash, rather than fail with an error as expected.
- Partitioning: A query result was not sorted if both DISTINCT and ORDER BY were used and the underlying table was partitioned.
- Partitioning: Inserting any number of rows into an ARCHIVE table that used more than 1000 partitions and then attempting to drop the table caused the MySQL Server to fail.
- Replication: When using GTIDs and binary log auto-positioning, the master had to scan all binary logs whenever the slave reconnected (due to reasons such as I/O thread failure or a change of master) before it could send any events to slave. Now, the master starts from the oldest binary log that contains any GTID not found on the slave.
- Replication: When the server version of the master was greater than or equal to 10, replication to a slave having a lower server version failed.
- Replication: When replicating to a MySQL 5.6 master to an older slave, Error 1193 (ER_UNKNOWN_SYSTEM_VARIABLE) was logged with a message such as Unknown system variable 'SERVER_UUID' on master, maybe it is a *VERY OLD MASTER*. This message has been improved to include more information, similar to this one: Unknown system variable 'SERVER_UUID' on master. A probable cause is that the variable is not supported on the master (version: 5.5.31), even though it is on the slave (version: 5.6.11).
- Replication: A zero-length name for a user variable (such as @``) was incorrectly considered to be a sign of data or network corruption when reading from the binary log.
- Replication: When MTS is on and transactions are being applied, the slave coordinator would hang when encountering a checksum error on a transaction event. This was due to a deadlock situation in which the coordinator assumed a normal stop while a worker waited for the coordinator to dispatch more events. For debug builds, the problem appeared as an assertion failure, which was due to the coordinator not setting thd->is_error() when encountering an error.
- Replication: mysqlbinlog can connect to a remote server and read its binary logs. In MySQL 5.6 and later, this tool can also wait for the server to generate and send additional events, in practice behaving like a slave connecting to a master. In cases where the server sent a heartbeat, mysqlbinlog was unable to handle it properly. As a consequence, mysqlbinlog failed at this point, without reading any more events from the server. To fix this problem, mysqlbinlog now ignores any binary log events of type HEARTBEAT_LOG_EVENT that it receives.
- Replication: STOP SLAVE could cause a deadlock when issued concurrently with a statement such as SHOW STATUS that retrieved the values for one or more of the status variables Slave_retried_transactions, Slave_heartbeat_period, Slave_received_heartbeats, Slave_last_heartbeat, or Slave_running.
- Replication: Using the --replicate-* options (see Replication Slave Options and Variables) could in some cases lead to a memory leak on the slave.
- Replication: Backtick (`) characters were not always handled correctly in internally generated SQL statements, which could sometimes lead to errors on the slave.
- Replication: The session-level value for gtid_next was incorrectly reset on the slave for all rollbacks, which meant that GTIDs could be lost for multi-statement transactions, causing the slave to stop with an ER_GTID_NEXT_TYPE_UNDEFINED_GROUP error. Now this is done only when a complete transaction is being rolled back, or when autocommit is enabled.
- Replication: In order to provision or to restore a server using GTIDs, it is possible to set gtid_purged to a given GTID set listing the transactions that were imported. This operation requires that the global gtid_executed and gtid_purged server system variables are empty. (This is done in order to avoid the possibility of overriding server-generated GTIDs.)
- The error message GTID_PURGED can only be set when GTID_EXECUTED is empty that was raised when this requirement was not met could be confusing or misleading because it did not specify the scope of the affected variables. To prevent this from happening, error messages that refer to variables relating to GTIDs now specify the scope of any such variables when they do so.
- Replication: In certain cases, the dump thread could send a heartbeat out of synchronisation with format description events. One of the effects of this issue what that, after provisioning a new server from a backup data directory and setting --gtid-mode=ON and enabling autopositioning (see CHANGE MASTER TO Syntax), replication failed to start, with the error Read invalid event from master.... The same problem could also cause GTID-based replication to fail due to skipped events following a unplanned shutdown of the master.
- Replication: In some cases, when the slave could not recognize the server version of the master, this could cause the slave to fail.
- Replication: Table IDs used in replication were defined as type ulong on the master and uint on the slave. In addition, the maximum value for table IDs in binary log events is 6 bytes (281474976710655). This combination of factors led to the following issues:
> Data could be lost on the slave when a table was assigned an ID greater than uint.
> Table IDs greater than 281474976710655 were written to the binary log as 281474976710655.
> This led to a stopped slave when the slave encountered two tables having the same table ID.
- To fix these problems, IDs are now defined by both master and slave as type ulonglong but constrained to a range of 0 to 281474976710655, restarting from 0 when it exceeds this value.
- Replication: Internal objects used for relay log information were only partially deleted before freeing their memory.
- Replication: It was possible in certain cases—immediately after detecting an EOF in the dump thread read event loop, and before deciding whether to change to a new binary log file—for new events to be written to the binary log before this decision was made. If log rotation occurred at this time, any events that occurred following EOF detection were dropped, resulting in loss of data. Now in such cases, steps are taken to make sure that all events are processed before allowing the log rotation to take place.
- Replication: If the disk becomes full while writing to the binary log, the server hangs until space is freed up manually. It was possible after this was done for the MySQL server to fail, due to an internal status value being set when not needed. Now in such cases, rather than trying to set this status, a warning is written in the error log instead.
- Microsoft Windows: In Shared Memory mode, the MySQL Server could crash when receiving requests from multiple threads.
- Failure to handle a full-text search wildcard properly could cause the server to exit.
- InnoDB now reports row and table locks to the thread pool plugin. Deadlocks within a thread group could occur otherwise.
- SHOW ENGINE PERFORMANCE_SCHEMA STATUS could report incorrect memory-allocation values when the correct values exceeded 4GB.
- Performance Schema statement tokenization overhead was reduced.
- A long database name in a GRANT statement could cause the server to exit.
- On Linux, a race condition involving epoll() could cause the thread pool plugin to miss events. This was most likely on systems with greater than 16 cores.
- The server could exit if a prepared statement attempted to create a table using the name of an existing view while an SQL handler was opened.
- For debug builds, checking of password constraints could raise an assertion for statements that updated passwords.
- The BUILD-CMAKE file in MySQL distributions was updated with the correct URL for CMake information.
- A Valgrind failure could occur if a CREATE USER statement was logged to the general query log and the old_passwords system variable was set to 2.
- The optimizer's attempt to remove redundant subquery clauses raised an assertion when executing a prepared statement with a subquery in the ON clause of a join in a subquery.
- Very small join_buffer_size values could cause an assertion to be raised.
- Some aggregate queries attempted to allocate excessive memory.
- Incorrect results were returned if a query contained a subquery in an IN clause which contained an XOR operation in the WHERE clause.
- For debug builds, an assertion could be raised if a statement failed with autocommit enabled just before an XA START statement was issued.
- Conversion of numeric values to BIT could yield unexpected results.
- Certain legal HAVING clauses were rejected as invalid.
- Fixed warnings when compiling with XCode 4.6. Fixed warnings when compiling when the _XOPEN_SOURCE or isoctal macro was already defined in the environment.
- Queries using range predicates that were evaluated using the LooseScan semi-join strategy could return duplicate rows.
- For upgrade operations, RPM packages produced unnecessary errors about being unable to access .err files.
- In the range optimizer, an index merge failure could cause a server exit.
- A full-text query using Boolean mode could return zero results in some cases where the search term was a quoted phrase:
- If the quoted phrase was preceded by a + sign. For example, this combination of a Boolean + operator and a phrase would return zero results:
where match(content) against('+"required term due to plus sign"' in boolean mode)
If the quoted phrase contained any stopwords. For example, the stopword "the" inside the phrase caused the query to return zero results:
where match(content) against('"stopword inside the phrase"' in boolean mode)
- For debug builds, the server could exit due to incorrect calculation of applicable indexes for a join that involved const tables.
- A bug in range optimization sometimes led to incorrect condition calculation for index merge union. This could lead to missing rows.
- The Performance Schema could return incorrect values for the PROCESSLIST_INFO column of the threads table.
- Invocation of the range optimizer for a NULL select caused the server to exit.
- mysql_config --libs displayed incorrect output.
- For a CREATE TABLE (... col_name TIMESTAMP DEFAULT CURRENT_TIMESTAMP ...) ... SELECT statement for which the SELECT did not provide a value for the TIMESTAMP column, that column was set to '0000-00-00 00:00:00', not the current timestamp.
- yaSSL did not perform proper padding checks, but instead examined only the last byte of plaintext and used it to determine how many bytes to remove.
- Using GROUP BY WITH ROLLUP in a prepared statement could cause the server to exit.
- If, in a SELECT, the HAVING clause contained a function call which itself contained an alias to a selected expression, the server could sometimes exit.
- Setting the slave_rows_search_algorithms system variable to an inappropriate value could cause the server to exit.
- Directory name manipulation could result in stack overflow on Mac OS X and Windows.
- with statement-based binary logging, dropping a TEMPORARY InnoDB table could cause a segmentation fault.
- For debug builds, if the server was started with binary logging disabled, executing SHOW RELAYLOG EVENTS from within a stored procedure raised an assertion.
- The query parser leaked memory for some syntax errors.
- With the thread pool plugin enabled, large numbers of connections could lead to a Valgrind panic or failure of clients to be able to connect.
- The server executed EXPLAIN FORMAT=JSON for some malformed queries improperly.
- Performance Schema instrumentation was missing for slave worker threads.
- The initial test database contained a dummy.bak file that prevented DROP DATABASE from working. This file is no longer included. Also, a db.opt file is now included that contains these lines:
- Setting a system variable to DEFAULT could cause the server to exit.
- SET PASSWORD and GRANT ... IDENTIFIED BY have no effect on the password of a user who is authenticated using an authentication plugin that accesses passwords stored externally to the mysql.user table. But attempts to change the password of such a user produced no warning, leading to the impression that the password had been changed when it was not. Now MySQL issues an ER_SET_PASSWORD_AUTH_PLUGIN warning to indicate that the attempt was ignored.
- For debug builds, creating an InnoDB table in strict SQL mode that violated the maximum key length limit caused the server to exit.
- Issuing a PREPARE statement using certain combinations of stored functions and user variables caused the server to exit.
- Joins of exactly 32 tables and containing a HAVING clause returned an empty result.
- A mysys library string-formatting routine could mishandle width specifiers.
- The --character-set-server option could set connection character set system variables to values such as ucs2 that are not permitted.
- During shutdown, the server could attempt to lock an uninitialized mutex.
- The --default-authentication-plugin option permitted invalid plugin values, and did not always set the old_passwords system variable to a value appropriate for the named plugin.
- Under some circumstances, mysql --secure-auth permitted passwords to be sent to the server using the old (pre-4.1) hashing format.
- With index condition pushdown enabled, queries for which the pushed-down condition contained no columns in the used index could be slow.
- Table creation operations added entries to the Performance Schema file_instances table, but these were not always removed for table drop operations.
- In special cases, the optimizer did not consider indexes that were applicable to query processing, resulting in potentially suboptimal execution and incorrect EXPLAIN output.
- A query with an EXISTS/IN/ALL/ANY subquery with an ORDER BY clause ordering by an outer column of type BLOB that is not in the select list caused an assertion to fire.
- Creating an InnoDB table with a FULLTEXT index could encounter a serious error if the table name contained nonalphanumeric characters.
- Enabling the query cache during high client contention could cause the server to exit.
- The server sometimes failed to respect MAX_CONNECTIONS_PER_HOUR limits on user connections.
- The optimizer could return incorrect results after transforming an IN subquery with aggregate functions to an EXISTS subquery.
- When a client program loses the connection to the MySQL server or if the server begins a shutdown after the client has executed mysql_stmt_prepare(), the next mysql_stmt_prepare() returns an error (as expected) but subsequent mysql_stmt_execute() calls crash the client.
- Previously, if multiple --login-path options were given, mysql_config_editor ignored all but the last one. Now multiple --login-path options result in an error.
- SET PASSWORD for anonymous users did not work correctly.
- SHOW COLUMNS on a view defined as a UNION of Geometry columns could cause the server to exit.
- The sha256_password_private_key_path and sha256_password_public_key_path system variables indicate key files for the sha256_password authentication plugin, but the server failed to properly check whether the key files were valid. Now in the event that either key file is invalid, the server logs an error and exits.
- SET var_name = VALUES(col_name) could cause the server to exit. This syntax is now prohibited because in SET context there is no column name and the statement returns ER_BAD_FIELD_ERROR.
- The COM_CHANGE_USER command in the client/server protocol did not properly use the character set number in the command packet, leading to incorrect character set conversion of other values in the packet.
- Invoking the FORMAT() function with a locale and a very large number could cause the server to exit.
- yaSSL rejected some valid server SSL certificates.
- Certain plugin-related conditions can make a user account unusable:
> The account requires an authentication plugin that is not loaded.
> The account requires the sha256_password authentication plugin but the server was started with neither SSL nor RSA enabled as required by this plugin.
- The server now checks those conditions by default and produces warnings for unusable accounts. This checking slows down server initialization and FLUSH PRIVILEGES, so it is made optional by means of the new validate_user_plugins system variable. This variable is enabled by default, but if you do not require the additional checking, you can disable it at startup to avoid the performance decrement.
- Passing an unknown time zone specification to CONVERT_TZ() resulted in a memory leak.
- The obsolete linuxthreads.txt and glibc-2.2.5.patch files in the Docs directory of MySQL distributions have been removed.
- mysql_install_db did not escape '_' in the host name for statements written to the grant tables.
- mysqld_safe used the nonportable -e test construct.
- An out-of-memory condition could occur while handling an out-of-memory error, leading to recursion in error handling.
- The optimizer used loose index scan for some queries for which this access method is inapplicable.
- If a dump file contained a view with one character set and collation defined on a view with a different character set and collation, attempts to restore the dump file failed with an “illegal mix of collations” error.
- The REPLACE() function produced incorrect results when a user variable was supplied as an argument and the operation was performed on multiple rows.
- UNION type conversion could incorrectly turn unsigned values into signed values.
- UNION ALL on BLOB columns could produce incorrect results.
- View access in low memory conditions could raise a debugging assertion.
- Queries with many values in a IN() clause were slow due to inclusion of debugging code in non-debugging builds.
- Setting max_connections to a value less than the current number of open connections caused the server to exit.
- Some table I/O performed by the server when calling a storage engine were missing from the statistics collected by the Performance Schema.
- For debug builds, some queries with SELECT ... FROM DUAL nested subqueries raised an assertion.
- Nonspatial indexes only support exact-match lookups for spatial columns, but the optimizer incorrectly used range access in some cases, leading to incorrect results.
- If mysql is built with the bundled libedit library, the library is built as static code, to avoid linking to a different dynamic version at runtime. Dynamic linking could result in use of a different, incompatible version and a segmentation fault.
- The --log-slow-admin-statements and --log-slow-slave-statements command options now are exposed at runtime as the log_slow_admin_statements and log_slow_slave_statements system variables. Their values can be examined using SHOW VARIABLES. The variables are dynamic, so their values can can be set at runtime. (The options were actually replaced by the system variables, but as system variables can be set at server startup, no option functionality is lost.)
- For arguments with fractional seconds greater than six decimals, SEC_TO_TIME() truncated, rather than rounding as it should have.
- MySQL failed to build if configured with WITH_LIBWRAP enabled.
- If the server was started without a --datadir option, SHOW VARIABLES could show an empty value for the datadir system variable.
- Configuring with -DWITH_SSL=/path/to/openssl resulted in link errors due to selection of the incorrect libcrypto.
- ALTER TABLE tbl_name ADD COLUMN col_name TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP inserted 0000-00-00 00:00:00 rather than the current timestamp if the alteration was done in place rather than by making a table copy.
- If the server was started with --skip-grant-tables, ALTER USER ... PASSWORD EXPIRE caused the server to exit.
- CMake did not check whether the system zlib had certain functions required for MySQL, resulting in build errors. Now it checks and falls back to the bundled zlib if the functions are missing.
- mysql_install_db did not work in Solaris 10 sparse root zones.
- or EXPLAIN DELETE and EXPLAIN UPDATE the possible_keys column listed all indexes, not just the applicable indexes.
- The Perl version of mysql_install_db mishandled some error messages.
- Handling of SQL_CALC_FOUND_ROWS in combination with ORDER BY and LIMIT could lead to incorrect results for FOUND_ROWS().
- Adding an ORDER BY clause following an IN subquery could cause duplicate rows to be returned.
- If INET6_NTOA() or INET6_ATON() returned NULL for a row in a result set, following rows also returned NULL.
- A statement with an aggregated, nongrouped outer query and an aggregated, nongrouped subquery in the SELECT list could return incorrect results.
- With explicit_defaults_for_timestamp enabled, inserting NULL into a TIMESTAMP NOT NULL column now produces an error (as it already did for other NOT NULL data types), instead of inserting the current timestamp.