The following list provides an overview of significant feature additions and changes first made in MySQL Cluster NDB 6.3. For more detailed information about all feature changes and bugfixes made in MySQL Cluster NDB 6.3, see http://dev.mysql.com/doc/relnotes/mysql-cluster/7.1/en/mysql-cluster-news-6-3.html.
Conflict detection and resolution. It is now possible to detect and resolve conflicts that arise in multi-master replication scenarios, such as circular replication, when different masters may try to update the same row on the slave with different data. Both “greatest timestamp wins” and “same timestamp wins” scenarios are supported. For more information, see Section 8.11, “MySQL Cluster Replication Conflict Resolution”.
Recovery of “one master, many slaves” replication setups.
Recovery of multi-way replication setups (“one
master, many slaves”) is now supported using the
--ndb-log-orig server option and changes
See Section 8.4, “MySQL Cluster Replication Schema and Tables”,
for more information.
Enhanced selection options for transaction coordinator.
New values and behaviors are introduced for
greater flexibility when an SQL node chooses a transaction
coordinator. For more information, see the description of
in Section 5.4.3, “MySQL Cluster System Variables”.
Replication heartbeats facilitate the task of monitoring
and detecting failures in master-slave connections in real
time. This feature is implemented using a new
clause for the
CHANGE MASTER TO statement
and the addition of two status variables
For more information, see
CHANGE MASTER TO Syntax.
NDB thread locks.
It is possible to lock
execution threads and maintenance threads (such as file
system and other operating system threads) to specific
CPUs on multiprocessor data node hosts, and to leverage
Improved performance of updates using primary keys or unique keys. The number of unnecessary reads when performing a primary key or unique key update has been greatly reduced. Since it is seldom necessary to read a record prior to an update, this can yield a considerable improvement in performance. In addition, primary key columns are no longer written to when not needed during update operations.
Improved SQL statement performance metrics.
system status variable measures the number of round trips
made by SQL statements to the
NDB kernel, providing an
improved metric for determining efficiency with which
statements are executed. For more information, see
Cluster Status Variables:
Compressed LCPs and backups.
Compressed local checkpoints and backups can save 50% or
more of the disk space used by uncompressed LCPs and
backups. These can be enabled using the two new data node
OPTIMIZE TABLE support with
OPTIMIZE TABLE is supported
for dynamic columns of in-memory
NDB tables. In such cases, it
is no longer necessary to drop (and possibly to re-create)
a table, or to perform a rolling restart, in order to
recover memory from deleted rows for general re-use by
Cluster. The performance of
Cluster tables can be tuned by adjusting the value of the
ndb_optimization_delay system variable,
which controls the number of milliseconds to wait between
processing batches of rows by
OPTIMIZE TABLE. In
OPTIMIZE TABLE on
NDBCLUSTER table can be
interrupted by, for example, killing the SQL thread
Batching of transactions.
It is possible to cause statements occurring within the
same transaction to be run as a batch by setting the
ON. To use
must be set to
OFF. Batch sizes can be controlled
--ndb-batch-size option for
mysqld. For additional information, see
Section 5.4.2, “MySQL Server Options for MySQL Cluster”,
and Section 5.4.3, “MySQL Cluster System Variables”.
Attribute promotion with ndb_restore.
It is possible using ndb_restore to
restore data reliably from a column of a given type to a
column that uses a “larger” type. This is
sometimes referred to as attribute
promotion. For example, MySQL Cluster backup
data that originated in a
SMALLINT column can be
restored to a
BIGINT column. See
Section 6.19, “ndb_restore — Restore a MySQL Cluster Backup”, for
Parallel data node recovery. Recovery of multiple data nodes can now be done in parallel, rather than sequentially. In other words, several data nodes can be restored concurrently, which can often result in much faster recovery times than when they are restored one at a time.
Increased local checkpoint efficiency. Only 2 local checkpoints are stored, rather than 3, lowering disk space requirements and the size and number of redo log files.
NDBCLUSTER table persistence control.
NDB tables can
be controlled using the session variables
NDB tables not to be
checkpointed to disk;
ndb_table_temporary does the same, and
in addition, no schema files are created. See
Section 5.4.1, “MySQL Cluster mysqld Option and Variable Reference”.
Epoll support (Linux only). Epoll is an improved method for handling file descriptors, which is more efficient than scanning to determine whether a file descriptor has data to be read. (The term epoll is specific to Linux and equivalent functionality is known by other names on other platforms such as Solaris and FreeBSD.) Currently, MySQL Cluster supports this functionality on Linux only.
Distribution awareness (SQL nodes).
In MySQL Cluster NDB 6.3, SQL nodes can take advantage of
awareness. Here we provide a brief example showing
how to design a table to make a given class of queries
distrubtion-aware. Suppose an
t1 has the following schema:
CREATE TABLE t1 ( userid INT NOT NULL, serviceid INT NOT NULL AUTO_INCREMENT PRIMARY KEY, data VARCHAR(255) ) ENGINE=NDBCLUSTER;
Suppose further that most of the queries to be used in our
application test values of the
column of this table. The form of such a query looks
something like this:
columnsFROM t1 WHERE userid
In this query,
represents some relational operator, such as
>, and so on. Queries using
IN and a list of values can also be used:
columnsFROM t1 WHERE userid IN
To make use of distribution awareness, we need to make the
userid column part of the table's
primary key, then explicitly partition the table with this
column being used as the partitioning key. (Recall that for
a partitioned table having one or more unique keys, all
columns of the table's partitioning key must also be
part of all of the unique keys—for more information
and examples, see
Partitioning Keys, Primary Keys, and Unique Keys.)
In other words, the table schema should be equivalent to the
CREATE TABLE t1 ( userid INT NOT NULL, serviceid INT NOT NULL AUTO_INCREMENT, data VARCHAR(255), PRIMARY KEY p (userid,serviceid) ) ENGINE=NDBCLUSTER PARTITION BY KEY(userid);
When the table is partitioned in this way, all rows having
userid value are found on the
same node group, and the MySQL Server can immediately select
the optimal node to use as the transaction coordinator.
Realtime extensions for multiple CPUs.
When running MySQL Cluster data nodes on hosts with
multiple processors, the realtime extensions make it
possible to give priority to the data node process and
control on which CPU cores it should operate. This can be
done using the data node configuration parameters
Doing so properly can significantly lower response times
and make them much more predictable response. For more
information about using these parameters, see
Data Nodes: Realtime Performance Parameters
Fully automatic database discovery.
It is no longer a requirement for database autodiscovery
that an SQL node already be connected to the cluster at
the time that a database is created on another SQL node,
or for a
CREATE DATABASE or
SCHEMA statement to be issued on the new SQL
node after it joins the cluster.
Detection of NDB API client connection errors.
Beginning with MySQL Cluster NDB 6.3.20, the NDB
class adds the
methods for catching and diagnosing problems with NDB API
Restoring specific databases, tables, or columns from a MySQL Cluster
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 6.3.22, you can choose to restore only
specified tables or databases, or exclude specific tables
or databases from being restored, using the new
--exclude-databases. Beginning with MySQL
Cluster NDB 6.3.26, 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 6.19, “ndb_restore — Restore a MySQL Cluster Backup”.
Improved Disk Data file system configuration.
As of MySQL Cluster NDB 6.3.22, you can specify default
locations for MySQL Cluster Disk Data data files and undo
log files using the data node configuration parameters
This eliminates the need to use symbolic links to place
Disk Data files separately from other files in data node
file systems to improve Disk Data performance. For more
Disk Data file system parameters.
Automatic creation of Disk Data log file groups and tablespaces.
Beginning with MySQL Cluster NDB 6.3.22, using the data
node configuration parameters
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
Data object creation parameters.
Configuration parameter data dumps.
Starting with MySQL Cluster NDB 6.3.25, 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 permitted values,
and the sections of the
file in which the parameters apply. An additional
--xml switch causes
ndb_config to use XML rather than
plaintext output. Using ndb_config
--xml requires no access to a running
MySQL Cluster, any other programs, or any files. For more
information and examples, see
Section 6.7, “ndb_config — Extract MySQL Cluster Configuration Information”.
Per-table reporting of free space on disk.
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
6.3.27 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
Section 6.10, “ndb_desc — Describe NDB Tables”.
Improved restart times. Optimizations in redo log handling and other file system operations introduced in MySQL Cluster NDB 6.3.28 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 6.3 releases by a factor of 50 or more.
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 6.3.29, MySQL Cluster supports online upgrading of API nodes (including MySQL servers running as SQL nodes) before upgrading management nodes, data nodes, or both.
Before attempting to use this new upgrade functionality, see Section 7.5, “Performing a Rolling Restart of a MySQL Cluster”, for additional information, especially if you are planning an online upgrade from MySQL Cluster NDB 6.3 to MySQL Cluster NDB 7.0.
New replication conflict resolution strategy.
Beginning with MySQL Cluster NDB 6.3.31, the function
NDB$MAX_DELETE_WIN() is available to
implement “greatest timestamp, delete wins”
conflict resolution. See
for more information.
CHANGE MASTER TO option for circular
Beginning with MySQL Cluster NDB 6.3.31, the
CHANGE MASTER TO statement
which takes a comma-separated list of server IDs and
causes events originating from the corresponding servers
to be ignored. (Log rotation and log deletion events are
Heartbeat thread policy and priority.
Beginning with MySQL Cluster NDB 6.3.32, a new
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
option causes this program to include partition
in its output. Beginning with MySQL Cluster NDB 6.3.33,
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
Information about partition-to-node mappings can also be
obtained using the
method, also added in MySQL Cluster NDB 6.3.33.
Replication attribute promotion and demotion.
Beginning with MySQL Cluster NDB 6.3.33, 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
column on the slave, and to demote a
TEXT column to a
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
global server system variable.
For more information, see Attribute promotion and demotion (MySQL Cluster).
Incompatible change in NDB API event reporting.
Beginning with MySQL Cluster NDB 6.3.34, DDL events are no
longer reported on
objects by default. Instead such event reporting must be
enabled explicitly using the
method. For more information, see
Beginning with MySQL Cluster NDB 6.3.35, it is possible to
set a specific order for transmission of heartbeats
between data nodes, using the
data node configuration parameter introduced in this
version. This parameter can be useful in situations where
multiple data nodes are running on the same host and a
temporary disruption in connectivity between hosts would
otherwise cause the loss of a node group (and thus failure
of the cluster).
Relaxed ndb_restore column comparison rules. When restoring data, ndb_restore compares the attributes of a column for equality with the definition of the column in the target table. However, not all of these attributes need to be the same for ndb_restore to be meaningful, safe and useful. Beginning with MySQL Cluster NDB 6.3.35, ndb_restore automatically ignores differences in certain column attributes which do not necessarily have to match between the version of the column in a backup and the version of that column in the MySQL Cluster to which the column data is being restored. These attributes include the following:
The default value
The distribution key
In such cases, ndb_restore reports any such differences to minimize any chance of user error.
--add-drop-trigger option for
Beginning with MySQL Cluster NDB 6.3.38, this option can
be used to force all
TRIGGER statements in
mysqldump output to be preceded by a
IF EXISTS statement.
Skipping corrupted tables in
Beginning with MySQL Cluster NDB 6.3.40, you can cause
ndb_restore to ignore tables that are
corrupted due to missing blob parts tables by using the
option. When this option is used, such tables are skipped,
and the restoration of any remaining uncorrupted tables in
the backup continues.
Restoring from a NDB native backup to a differently-named database.
MySQL Cluster NDB 6.3.41 adds a new
option to ndb_restore, which makes it
possible to restore to a database having a different name
from that of the database in the backup. The option can be
used multiple times, and it is possible to restore from
more than one source database in the backup to a single
target database (although no protection against table or
other object name collision is provided).
See Section 6.19, “ndb_restore — Restore a MySQL Cluster Backup”, for more information.
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