Performance: Added support for pushing down joins to the NDB kernel for parallel execution across the data nodes, which can speed up execution of joins across NDB tables by a factor of 20 or more in some cases. Some restrictions apply on the types of joins that can be optimized in this way; in particular, columns to be joined must use exactly the same data type, and cannot be any of the BLOB or TEXT types. In addition, columns to be joined must be part of a table index or primary key. Support for this feature can be enabled or disabled using the ndb_join_pushdown server system variable (enabled by default); see the description of this variable for more information and examples.

As part of this improvement, the status variables Ndb_pushed_queries_defined, Ndb_pushed_queries_dropped, Ndb_pushed_queries_executed, and Ndb_pushed_reads also been introduced for monitoring purposes. You can also see whether a given join is pushed down using EXPLAIN. In addition, several new counters relating to push-down join performance have been added to the counters table in the ndbinfo database. For more information, see the descriptions of the status variables previously mentioned.

Important Change: MySQL user privileges can now be distributed automatically across all MySQL servers (SQL nodes) connected to the same MySQL Cluster. Previously, each MySQL Server's user privilege tables were required to use the MyISAM storage engine, which meant that a user account and its associated privileges created on one SQL node were not available on any other SQL node without manual intervention. MySQL Cluster now provides an SQL script file ndb_dist_priv.sql that can be found in share/mysql under the MySQL installation directory; loading this script creates a stored procedure mysql_cluster_move_privileges that can be used following initial installation to convert the privilege tables to the NDB storage engine, so that any time a MySQL user account is created, dropped, or has its privileges updated on any SQL node, the changes take effect immediately on all other MySQL servers attached to the cluster. Note that you may need to execute FLUSH PRIVILEGES on any SQL nodes with connected MySQL clients (or to disconnect and then reconnect the clients) in order for those clients to be able to see the changes in privileges.

Once mysql_cluster_move_privileges has been executed successfully, all MySQL user privileges are distributed across all connected MySQL Servers. MySQL Servers that join the cluster after this automatically participate in the privilege distribution.

ndb_dist_priv.sql also provides stored routines that can be used to verify that the privilege tables have been distributed successfully, and to perform other tasks.

For more information, see Distributed MySQL Privileges for MySQL Cluster.

Important Change: The default values for a number of MySQL Cluster data node configuration parameters have changed, to provide more resiliency to environmental issues and better handling of some potential failure scenarios, and to perform more reliably with increases in memory and other resource requirements brought about by recent improvements in join handling by NDB. The affected parameters are listed here:

In addition, when MaxNoOfLocalScans is not specified, the value computed for it automatically has been increased by a factor of 4 (that is, to 4 times MaxNoOfConcurrentScans, times the number of data nodes in the cluster).