MySQL Cluster on Windows (alpha).  MySQL Cluster is now available on an experimental basis for Windows operating systems. Features and behavior comparable to those found on platforms that are already supported — such as Linux and Solaris — are planned for MySQL Cluster on Windows. Currently, you must build from source, although we intend to start making Windows binaries available in the near future. To enable MySQL Cluster support on Windows, you must configure the build using the WITH_NDBCLUSTER_STORAGE_ENGINE option. For more information, see Installing MySQL from Source on Windows.

Ability to add nodes and node groups online.  Beginning with MySQL Cluster NDB 6.4.0, it is possible to add new node groups (and thus new data nodes) to a running MySQL Cluster without shutting down and reloading the cluster. As part of enabling this feature, a new command CREATE NODEGROUP has been added to the cluster management client and the functionality of the ALTER ONLINE TABLE ... REORGANIZE PARTITION SQL statement has been extended. For more information, see Section 5.11, “Adding MySQL Cluster Data Nodes Online”.

Data node multithreading support.  Beginning with MySQL Cluster NDB 6.4.0, a multithreaded version of the data node daemon, named ndbmtd, is available for use on data node hosts with multiple CPU cores. This binary is built automatically when compiling with MySQL Cluster support; no additional options other than those needed to provide MySQL Cluster support are needed when configuring the build. In most respects, ndbmtd functions in the same way as ndbd, and can use the same command-line options and configuration parameters. In addition, the new MaxNoOfExecutionThreads configuration parameter can be used to determine the number of data node process threads for ndbmtd. For more information, see Section 4.3, “ndbmtd — The MySQL Cluster Data Node Daemon (Multi-Threaded)”.

Configuration cache.  Formerly, MySQL Cluster configuration was stateless — that is, configuration information was reloaded from the cluster's global configuration file (usually config.ini) each time ndb_mgmd was started. Beginning with MySQL Cluster NDB 6.4.0, the cluster's configuration is cached internally, and the global configuration file is no longer automatically re-read when the management server is restarted. This behavior can be controlled via the three new management server options --configdir, --initial, and --reload. For more information about this change, see Section 3.2, “MySQL Cluster Configuration Files”. For more information about the new management server options, see Section 4.4, “ndb_mgmd — The MySQL Cluster Management Server Daemon”.

Snapshot options for backups.  Beginning with MySQL Cluster NDB 6.4.0, you can determine when performing a cluster backup whether the backup matches the state of the data when the backup was started or when it was completed, using the new options SNAPSHOTSTART and SNAPSHOTEND for the management client's START BACKUP command. See Section 5.3.2, “Using The MySQL Cluster Management Client to Create a Backup”, for more information.

Dynamic NDB transporter send buffer memory allocation.  Previously, the NDB kernel used a fixed-size send buffer for every data node in the cluster, which was allocated when the node started. Because the size of this buffer could not be changed after the cluster was started, it was necessary to make it large enough in advance to accomodate the maximum possible load on any transporter socket. However, this was an inefficient use of memory, since much of it often went unused. Beginning with MySQL Cluster NDB 6.4.0, send buffer memory is allocated dynamically from a memory pool shared between all transporters, which means that the size of the send buffer can be adjusted as necessary. This change is reflected by the addition of the configuration parameters TotalSendBufferMemory, ReservedSendBufferMemory, and OverLoadLimit, as well as a change in how the existing SendBufferMemory configuration parameter is used. For more information, see Section 3.2.13, “Configuring MySQL Cluster Send Buffer Parameters”.

Robust DDL operations.  Beginning with MySQL Cluster NDB 6.4.0, DDL operations (such as CREATE TABLE or ALTER TABLE) are protected from data node failures; in the event of a data node failure, such operations are now rolled back gracefully. Previously, if a data node failed while trying to perform a DDL operation, the MySQL Cluster data dictionary became locked and no further DDL statements could be executed without restarting the cluster.

IPv6 support in MySQL Cluster Replication.  Beginning with MySQL Cluster NDB 6.4.1, IPv6 networking is supported between MySQL Cluster SQL nodes, which makes it possible to replicate between instances of MySQL Cluster using IPv6 addresses. However, IPv6 is supported only for direct connections between MySQL servers; all connections within an individual MySQL Cluster must use IPv4. For more information, see Section 6.3, “Known Issues in MySQL Cluster Replication”.

Restoring specific databases, tables, or columns from a MySQL Cluster backup.  It is now possible to exercise more fine-grained control when restoring a MySQL Cluster from backup using ndb_restore. Beginning with MySQL Cluster NDB 6.4.3, you can choose to restore only specified tables or databases, or exclude specific tables or databases from being restored, using the new ndb_restore options --include-tables, --include-databases, --exclude-tables, and --exclude-databases. Beginning with MySQL Cluster NDB 7.0.7, it is also possible to restore to a table having fewer columns than the original using the --exclude-missing-columns option. For more information about all of these options, see Section 4.17, “ndb_restore — Restore a MySQL Cluster Backup”.

Improved Disk Data filesystem configuration.  As of MySQL Cluster NDB 6.4.3, you can specify default locations for MySQL Cluster Disk Data data files and undo log files using the data node configuration parameters FileSystemPathDD, FileSystemPathDataFiles, and FileSystemPathUndoFiles. This eliminates the need to use symbolic links in order to place Disk Data files separately from other files in data node filesystems to improve Disk Data performance. For more information, see Disk Data filesystem parameters.

Automatic creation of Disk Data log file groups and tablespaces.  Beginning with MySQL Cluster NDB 6.4.3, using the data node configuration parameters InitialLogFileGroup and InitialTablespace, you can cause the creation of a MySQL Cluster Disk Data log file group, tablespace, or both, when the cluster is first started. When using these parameters, no SQL statements are required to create these Disk Data objects. For more information, see Disk Data object creation parameters.

Improved internal message passing and record handling.  MySQL Cluster NDB 7.0 contains 2 changes that optimize the use of network connections by addressing the size and number of messages passed between data nodes, and between data nodes and API nodes, which can increase MySQL Cluster and application performance:

Both of these optimizations are internal to the NDB API, and so is transparent to applications; this is true whether an application uses the NDB API directly or does so indirectly through an SQL node.

Configuration parameter data dumps.  Starting with MySQL Cluster NDB 7.0.6, the ndb_config utility supports a --configinfo option that causes it to dump a list of all configuration parameters supported by the cluster, along with brief descriptions, information about the parameters' default and allowed values, and the sections of the config.ini file in which the parameters apply. An additional --xml switch causes ndb_config to use XML rather than plaintext output. Using ndb_config --configinfo or ndb_config --configinfo --xml requires no access to a running MySQL Cluster, any other programs, or any files. For more information and examples, see Section 4.6, “ndb_config — Extract MySQL Cluster Configuration Information”.

Per-table reporting of free space on disk.  The INFORMATION_SCHEMA.FILES table shows information about used and free space in MySQL Cluster Disk Data data files, but this information is not applicable to individual tables. In MySQL Cluster NDB 7.0.8 and later, the ndb_desc utility provides two additional columns in its output that show the amount of space allocated on disk for a given NDB table as well the amount of space that remains available for additional storage of disk-based column data for that table. For more information, see Section 4.9, “ndb_desc — Describe NDB Tables”.

Improved restart times.  Optimizations in redo log handling and other filesystem operations introduced in MySQL Cluster NDB 7.0.9 have the potential to reduce considerably the time required for restarts. While actual performance benefits observed in production setups will naturally vary depending on database size, hardware, and other conditions, our own preliminary testing has shown that these improvements can yield startup times that are faster than those typical of previous MySQL Cluster NDB 7.0 releases by a factor of 50 or more.

--nowait-nodes option for management servers.  Starting with MySQL Cluster NDB 7.0.10, it is possible to configure a cluster with two management servers, but to start the cluster using only one of them by starting the management node daemon with the --nowait-nodes option. The other management server can then be started at a later time to join the running MySQL Cluster.

Increased flexibility in online upgrade procedure.  Previously, when performing an upgrade of a running MySQL cluster, the order in which the types of cluster nodes had to be upgraded was very strict. However, beginning with MySQL Cluster NDB 7.0.10, MySQL Cluster supports online upgrading of API nodes (including MySQL servers running as SQL nodes) online upgrading management nodes, data nodes, or both.

New replication conflict resolution strategy.  Beginning with MySQL Cluster NDB 7.0.11, the function NDB$MAX_DELETE_WIN() is available to implement “greatest timestamp, delete wins” conflict resolution. See NDB$MAX_DELETE_WIN(column_name), for more information.

Improved lock handling for primary key lookups on BLOB tables.  A MySQL Cluster table stores all but the first 256 bytes of any BLOB or TEXT column values in a separate BLOB table; when executing queries against such tables, a shared lock is obtained. Prior to MySQL Cluster NDB 7.0.12, when the query used a primary key lookup and took place within a transaction, the lock was held for the duration of the transaction, even after no more data was being read from the NDB table. Now in such cases, the lock is released when all BLOB data associated with the table has been read. (Bug#49190)

Heartbeat thread policy and priority.  Beginning with MySQL Cluster NDB 7.0.13, a new configuration parameter HeartbeatThreadPriority makes it possible to set the policy and the priority for the heartbeat thread on management and API nodes.

Improved access to partitioning information.  The ndb_desc utility now provides additional information about the partitioning of data stored in MySQL Cluster. Beginning with MySQL Cluster NDB 7.0.13, the --blob-info option causes this program to include partition information for BLOB tables in its output. Beginning with MySQL Cluster NDB 7.0.14, the --extra-node-info option causes ndb_desc to include information about data distribution (that is, which table fragments are stored on which data nodes). Each of these options also requires the use of the --extra-partition-info option.

Information about partition-to-node mappings can also be obtained using the Table::getFragmentNodes() method, also added in MySQL Cluster NDB 7.0.14.

Replication attribute promotion and demotion.  Beginning with MySQL Cluster NDB 7.0.14, MySQL Cluster Replication supports attribute promotion and demotion when replicating between columns of different but similar types on the master and the slave. For example, it is possible to promote an INT column on the master to a BIGINT column on the slave, and to demote a TEXT column to a VARCHAR column.

The implementation of type demotion distinguishes between lossy and non-lossy type conversions, and their use on the slave can be controlled by setting the slave_type_conversions global server system variable.

For more information, see Attribute promotion and demotion (MySQL Cluster).