MySQL 5.5.23

[McLovin]

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

Change Log - Link.

# Functionality Added or Changed
* The MySQL-shared-compat RPM package enables users of Red Hat-privided mysql-*-5.1 RPM packages to migrate to Oracle-provided MySQL-*-5.5 packages. MySQL-shared-compat now replaces the Red Hat mysql-libs package by replacing libmysqlclient.so files of the latter package, thus satisfying dependencies of other packages on mysql-libs. This change affects only users of Red Hat (or Red Hat-compatible) RPM packages. Nothing is different for users of Oracle RPM packages.
# Bugs Fixed
* Security Fix: Bug #59533 was fixed.
* Performance: Partitioning: InnoDB Storage Engine: The statistics used by the optimizer for queries against partitioned InnoDB tables were based only on the first partition of each such table, leading to use of the wrong execution plan.
* Performance: InnoDB Storage Engine: Improved the performance of the DROP TABLE statement for InnoDB tables, especially on systems with a large buffer pool. The fix speeds up the processing for freeing entries in the adaptive hash index.
* InnoDB Storage Engine: Deleting a huge amount of data from InnoDB tables within a short time could cause the purge operation that flushes data from the buffer pool to stall. If this issue occurs, restart the server to work around it. This issue is only likely to occur on 32-bit platforms.
* InnoDB Storage Engine: If the server crashed during a TRUNCATE TABLE or CREATE INDEX statement for an InnoDB table, or a DROP DATABASE statement for a database containing InnoDB 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.
* InnoDB Storage Engine: When data was removed from an InnoDB table, newly inserted data might not reuse the freed disk blocks, leading to an unexpected size increase for the system tablespace or .ibd file (depending on the setting of innodb_file_per_table. The OPTIMIZE TABLE could compact a .ibd file in some cases but not others. The freed disk blocks would eventually be reused as additional data was inserted.
* Partitioning: After updating a row of a partitioned table and selecting that row within the same transaction with the query cache enabled, then performing a ROLLBACK, the same result was returned by an identical SELECT issued in a new transaction.
* Replication: Formerly, the default value shown for the Port column in the output of SHOW SLAVE HOSTS was 3306 whether the port had been set incorrectly or not set at all. Now, when the slave port is not set, 0 is used as the default. This change also affects the default used for the --report-port server option.
* Replication: The --relay-log-space-limit option was sometimes ignored. More specifically, when the SQL thread went to sleep, it allowed the I/O thread to queue additional events in such a way that the relay log space limit was bypassed, and the number of events in the queue could grow well past the point where the relay logs needed to be rotated. Now in such cases, the SQL thread checks to see whether the I/O thread should rotate and provide the SQL thread a chance to purge the logs (thus freeing space). Note that, when the SQL thread is in the middle of a transaction, it cannot purge the logs; it can only ask for more events until the transaction is complete. Once the transaction is finished, the SQL thread can immediately instruct the I/O thread to rotate.
* An infinite thread loop could develop within Performance Schema, causing the server to become unresponsive.
* Incorrect stored program caching could cause statements within a stored program that included a GROUP BY clause to return different results across multiple program invocations.
* Mishandling of NO_BACKSLASH_ESCAPES SQL mode within stored procedures on slave servers could cause replication failures.
* SAVEPOINT statements were incorrectly disallowed within XA transactions.
* The Performance Schema incorrectly displayed some backslashes in Windows file names (by doubling them).
* SHOW statements treated stored procedure, stored function, and event names as case sensitive.

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[McLovin]

# Bugs Fixed
* A regression bug in the optimizer could cause excessive disk usage for UPDATE statements.

Sources.

 

[McLovin]

* Functionality Added or Changed
- Important Change: The YEAR(2) data type is now deprecated because it is problematic. Support for YEAR(2) will be removed in a future release of MySQL.
* Bugs Fixed
- InnoDB: A race condition could cause assertion errors during a DROP TABLE statement for an InnoDB table. Some internal InnoDB functions did not correctly determine if a tablespace was missing; other functions did not handle the error code correctly if a tablespace was missing.
- InnoDB: If a row was deleted from an InnoDB table, then another row was re-inserted with the same primary key value, an attempt by a concurrent transaction to lock the row could succeed when it should have waited. This issue occurred if the locking select used a WHERE clause that performed an index scan using a secondary index.
- InnoDB: An assertion could be raised if an InnoDB table was moved to a different database using ALTER TABLE ... RENAME while the database was being dropped by DROP DATABASE.
- InnoDB: Using the KILL statement to terminate a query could cause an unnecessary message in the error log: [ERROR] Got error -1 when reading table table_name
- InnoDB: For an InnoDB table with a trigger, under the setting innodb_autoinc_lock_mode=1, sometimes auto-increment values could be interleaved when inserting into the table from two sessions concurrently. The sequence of auto-increment values could vary depending on timing, leading to data inconsistency in systems using replication.
- Replication: An event whose length exceeded the size of the master dump thread's max_allowed_packet caused replication to fail. This could occur when updating many large rows and using row-based replication. As part of this fix, a new server option --slave-max-allowed-packet is added, which permits max_allowed_packet to be exceeded by the slave SQL and I/O threads. Now the size of a packet transmitted from the master to the slave is checked only against this value (available as the value of the slave_max_allowed_packet server system variable), and not against the value of max_allowed_packet.
- Replication: Statements such as UPDATE ... WHERE primary_key_column = constant LIMIT 1 are flagged as unsafe for statement-based logging, despite the fact that such statements are actually safe. In cases where a great many such statements were run, this could lead to disk space becoming exhausted do to the number of such false warnings being logged. To prevent this from happening, a warning suppression mechanism is introduced. This warning suppression acts as follows: Whenever the 50 most recent ER_BINLOG_UNSAFE_STATEMENT warnings have been generated more than 50 times in any 50-second period, warning suppression is enabled. When activated, this causes such warnings not to be written to the error log; instead, for each 50 warnings of this type, a note is written to the error log stating The last warning was repeated N times in last S seconds. This continues as long as the 50 most recent such warnings were issued in 50 seconds or less; once the number of warnings has decreased below this threshold, the warnings are once again logged normally. The fix for this issue does not affect how these warnings are reported to MySQL clients; a warning is still sent to the client for each statement that generates the warning. This fix also does not make any changes in how the safety of any statement for statement-based logging is determined.
- Replication: After upgrading a replication slave to MySQL 5.5.18 or later, enabling the query cache eventually caused the slave to fail.
- The server did not build with gcc 4.7.
- Certain arguments to RPAD() could lead to “uninitialized variable” warnings.
- The presence of a file named .empty in the test database prevented that database from being dropped.
- For some subqueries that should be executed using a range scan on a non-primary index and required use of filesort, only the first execution of the subquery was done as a range scan. All following executions were done as full table scans, resulting in poor performance.
- The number of connection errors from a given host as counted by the server was periodically reset, with the result that max_connect_errors was never reached and invalid hosts were never blocked from trying to connect.
- File access by the ARCHIVE storage engine was not instrumented and thus not shown in Performance Schema tables.
- mysqlbinlog exited with no error code if file write errors occurred.
- Using CONCAT() to construct a pattern for a LIKE pattern match could result in memory corrupting and match failure.
- yaSSL rejected valid SSL certificates that OpenSSL accepts.
- Sessions could end up deadlocked when executing a combination of SELECT, DROP TABLE, KILL, and SHOW ENGINE INNODB STATUS.
- mysqldump could dump views and the tables on which they depend in such an order that errors occurred when the dump file was reloaded.

Sources.

 

[McLovin]

# Functionality Added or Changed
* The internal interface of the Thread Pool plugin has changed. Old versions of the plugin will work with current versions of the server, but versions of the server older than 5.5.28 will not work with current versions of the plugin.
# Bugs Fixed
* InnoDB: Certain information_schema tables originally introduced in MySQL 5.6 are now also available in MySQL 5.5 and MySQL 5.1: INNODB_BUFFER_PAGE, INNODB_BUFFER_PAGE_LRU, and INNODB_BUFFER_POOL_STATS.
* InnoDB: When a SELECT ... FOR UPDATE, UPDATE, or other SQL statement scanned rows in an InnoDB table using a < or <= operator in a WHERE clause, the next row after the affected range could also be locked. This issue could cause a lock wait timeout for a row that was not expected to be locked. The issue occurred under various isolation levels, such as READ COMMITTED and REPEATABLE READ.
* Partitioning: For tables using PARTITION BY HASH or PARTITION BY KEY, when the partition pruning mechanism encountered a multi-range list or inequality using a column from the partitioning key, it continued with the next partitioning column and tried to use it for pruning, even if the previous column could not be used. This caused partitions which possibly matched one or more of the previous partitioning columns to be pruned away, leaving partitions that matched only the last column of the partitioning key.
- This issue was triggered when both of the following conditions were met:
> The columns making up the table's partitioning key were used in the same order as in the partitioning key definition by a SELECT statement's WHERE clause as in the column definitions;
> The WHERE condition used with the last column of the partitioning key was satisfied only by a single value, while the condition testing some previous column from the partitioning key was satisfied by a range of values.
An example of a statement creating a partitioned table and a query against this for which the issue described above occurred is shown here:
CREATE TABLE t1 (
c1 INT,
c2 INT,
PRIMARY KEY(c2, c1)
) PARTITION BY KEY() # Use primary key as partitioning key
PARTITIONS 2;
SELECT * FROM t1 WHERE c2 = 2 AND c1 <> 2;
This issue is resolved by ensuring that partition pruning skips any remaining partitioning key columns once a partition key column that cannot be used in pruning is encountered.
* Partitioning: The buffer for the row currently read from each partition used for sorted reads was allocated on open and freed only when the partitioning handler was closed or destroyed. For SELECT statements on tables with many partitions and large rows, this could cause the server to use excessive amounts of memory. This issue has been addressed by allocating buffers for reads from partitioned tables only when they are needed and freeing them immediately once they are no longer needed. As part of this fix, memory is now allocated for reading from rows only in partitions that have not been pruned.
* Replication: On 64-bit Windows platforms, values greater than 4G for the max_binlog_cache_size and max_binlog_stmt_cache_size system variables were truncated to 4G. This caused LOAD DATA INFILE to fail when trying to load a file larger than 4G in size, even when max_binlog_cache_size was set to a value greater than this.
* Replication: In master-master replication with --log-slave-updates enabled, setting a user variable and then performing inserts using this variable caused the Exec_master_log_position column in the output of SHOW SLAVE STATUS not to be updated.
* The RPM spec file now also runs the test suite on the new binaries, before packaging them.
* The libmysqlclient_r client library exported symbols from yaSSL that conflict with OpenSSL. If a program linked against that library and libcurl, it could crash with a segmentation fault.
* The argument for LIMIT must be an integer, but if the argument was given by a placeholder in a prepared statement, the server did not reject noninteger values such as '5'.
* The Thread Pool plugin did not respect the wait_timeout timeout for client sessions.
* CHECK TABLE and REPAIR TABLE could crash if a key definition differed in the .frm and .MYI files of a MyISAM table. Now the server produces an error.
* A query for a FEDERATED table could return incorrect results when the underlying table had a compound index on two columns and the query included an AND condition on the columns.
* mysqlhotcopy failed for databases containing views.
* The argument to the --ssl-key option was not verified to exist and be a valid key. The resulting connection used SSL, but the key was not used.
* Adding a LIMIT clause to a query containing GROUP BY and ORDER BY could cause the optimizer to choose an incorrect index for processing the query, and return more rows than required.
* mysqlbinlog did not accept input on the standard input when the standard input was a pipe.

Sources.