Incompatible Change: MySQL Cluster: The internal specifications for columns in NDB tables has changed to allow compatibility with future MySQL Cluster releases that are expected to implement online adding and dropping of columns. This change is not backward compatible with earlier versions of MySQL Cluster.

See the related note in MySQL Cluster 4.1 Upgrade and Downgrade Compatibility, for important information prior to upgrading a MySQL Cluster to MySQL 5.1.18 or later from MySQL 5.1.17 or earlier.

See also Bug#28205

Cluster Replication: Incompatible Change: The definition of the mysql.ndb_apply_status table has changed such that an online upgrade is not possible from MySQL 5.1.17 or earlier for a replication slave cluster; you must shut down all SQL nodes as part of the upgrade procedure. See MySQL Cluster 4.1 Upgrade and Downgrade Compatibility before upgrading for details.

For more information about the changes to mysql.ndb_apply_status see Cluster Replication Schema and Tables.

Incompatible Change: Prior to this release, when DATE values were compared with DATETIME values, the time portion of the DATETIME value was ignored, or the comparison could be performed as a string compare. Now a DATE value is coerced to the DATETIME type by adding the time portion as 00:00:00. To mimic the old behavior, use the CAST() function to cause the comparison operands to be treated as previously. For example: SELECT date_col = CAST(NOW() AS DATE);. (Bug#28929)

Incompatible Change: The INFORMATION_SCHEMA.EVENTS and mysql.event tables have been changed to facilitate replication of events. When upgrading to MySQL 5.1.18, you must run mysql_upgrade prior to working with events. Until you have done so, any statement relating to the Event Scheduler or these tables (including SHOW EVENTS) will fail with the errors Expected field status at position 12 to have type enum ('ENABLED','SLAVESIDE_DISABLED','DISABLED'), found enum('ENABLED','DISABLED') and Table mysql.event is damaged. Can not open.

These changes were made as part of fixes for the following bugs:

For more information, see Replication of Invoked Features. (Bug#17857, Bug#16421, Bug#20384, Bug#17671)

Security Fix: The requirement of the DROP privilege for RENAME TABLE was not enforced. (Bug#27515, CVE-2007-2691)

Security Fix: If a stored routine was declared using SQL SECURITY INVOKER, a user who invoked the routine could gain privileges. (Bug#27337, CVE-2007-2692)

Security Fix: A user with only the ALTER privilege on a partitioned table could obtain information about the table that should require the SELECT privilege. (Bug#23675, CVE-2007-2693)