Added option --sigint-ignore to the mysql command line client to make it ignore SIGINT signals (typically the result of the user pressing Control-C).

InnoDB: Added the startup option and settable global variable innodb_max_purge_lag for delaying INSERT, UPDATE and DELETE operations when the purge operations are lagging. The default value of this parameter is zero, meaning that there are no delays. See Section 14.2.13, “Implementation of Multi-Versioning”.

InnoDB: The innodb_autoextend_increment startup option that was introduced in release 4.1.5 was made a settable global variable. (Bug#5736)

InnoDB: If DROP TABLE is invoked on an InnoDB table for which the .ibd file is missing, print to error log that the table was removed from the InnoDB data dictionary, and allow MySQL to delete the .frm file. Maybe DROP TABLE should issue a warning in this case.

TIMESTAMP columns now can store NULL values. To create such a column, you must explicitly specify the NULL attribute in the column specification. (Unlike all other data types, TIMESTAMP columns are NOT NULL by default.)

Now if ALTER TABLE converts one AUTO_INCREMENT column to another AUTO_INCREMENT column it preserves zero values (this includes the case that we don't change such column at all).

Now if ALTER TABLE converts some column to TIMESTAMP NOT NULL column it converts NULL values to current timestamp value (One can still get old behavior by setting system TIMESTAMP variable to zero).

On Windows, the MySQL configuration files included in the package now use .ini instead of .cnf as the file name suffix.

Fixed a bug that caused the server to crash on attempt to execute a prepared statement with a subquery inside a boolean expression. (Bug#5987)

Fixed a bug that caused the server to sometimes choose non-optimal execution plan for a prepared statement executed with changed placeholder values. (Bug#6042)

InnoDB: Make the check for excessive semaphore waits tolerate glitches in the system clock (do not crash the server if the system time is adjusted while InnoDB is under load.). (Bug#5898)

InnoDB: Fixed a bug in the InnoDB FOREIGN KEY parser that prevented ALTER TABLE of tables containing ‘#’ in their names. (Bug#5856)

InnoDB: Fixed a bug that prevented ALTER TABLE t DISCARD TABLESPACE from working. (Bug#5851)

InnoDB: SHOW CREATE TABLE now obeys the SET SQL_MODE=ANSI and SET SQL_QUOTE_SHOW_CREATE=0 settings. (Bug#5292)

InnoDB: Fixed a bug that caused CREATE TEMPORARY TABLE ... ENGINE=InnoDB to terminate mysqld when running in innodb_file_per_table mode. Per-table tablespaces for temporary tables from now on are created in the temporary directory of mysqld. (Bug#5137)

InnoDB: Fixed some (not all) UTF-8 bugs in column prefix indexes. (Bug#5975)

InnoDB: If one updated a column so that its size changed, or updated it to an externally stored (TEXT or BLOB) value, then ANOTHER externally stored column would show up as 512 bytes of good data + 20 bytes of garbage in a consistent read that fetched the old version of the row. (Bug#5960)

InnoDB: Change error code to HA_ERR_ROW_IS_REFERENCED if we cannot DROP a parent table referenced by a FOREIGN KEY constraint; this error number is less misleading than the previous number HA_ERR_CANNOT_ADD_FOREIGN, but misleading still. (Bug#6202)

Fixed REVOKE ALL PRIVILEGES, GRANT OPTION FROM user so that all privileges are revoked correctly. (Bug#5831)

Fixed a bug that caused the server to crash when character set conversion was implicitly used in prepared mode; for example, as in 'abc' LIKE CONVERT('abc' as utf8). (Bug#5688)

The mysql_change_user() C API function now frees all prepared statements associated with the connection. (Bug#5315)

Fixed a bug when inserting NULL into an AUTO_INCREMENT column failed, when using prepared statements. (Bug#5510)

Fixed slave SQL thread so that the SET COLLATION_SERVER... statements it replicates don't advance its position (so that if it gets interrupted before the actual update query, it later redoes the SET). (Bug#5705)

Fixed that if the slave SQL thread found a syntax error in a query (which should be rare, as the master parsed it successfully), it stops. (Bug#5711)

Fixed that if a write to a MyISAM table fails because of a full disk or an exceeded disk quota, it prints a message to the error log every 10 minutes, and waits until disk space becomes available. (Bug#3248)

Now MySQL does not prefer columns, which are mentioned in select list but are renamed, over columns from other tables participating in FROM clause when it resolves GROUP BY clause (for example, SELECT t1.a AS c FROM t1, t2 ORDER BY a produces an error if both t1 and t2 tables contain a column). (Bug#4302)

Behavior of ALTER TABLE converting column containing NULL values to AUTO_INCREMENT column is no longer affected by NO_AUTO_VALUE_ON_ZERO mode. (Bug#5915).