A number of features for MySQL Cluster were implemented in MySQL 5.1 through MySQL 5.1.23, when support for MySQL Cluster was moved to MySQL Cluster NDB. All of the features in the following list are also available in all MySQL Cluster NDB (6.1 and later) releases.
Integration of MySQL Cluster into MySQL Replication.
MySQL Cluster Replication makes it possible to replicate
from one MySQL Cluster to another. Updates on any SQL node
(MySQL server) in the cluster acting as the master are
replicated to the slave cluster; the state of the slave
side remains consistent with the cluster acting as the
master. This is sometimes referred to as
asynchronous replication between
clusters, providing geographic
redundancy. It is also possible to replicate
from a MySQL Cluster acting as the master to a standalone
MySQL server acting as the slave, or from a standalone
MySQL master server to to a slave cluster; in either of
these cases, the standalone MySQL server uses a storage
engine other than
Multi-master replication setups such as circular
replication are also supported.
Support for storage of rows on disk.
data on disk is now supported. Indexed columns, including
the primary key hash index, must still be stored in RAM;
however, all other columns can be stored on disk.
In MySQL 5.0, an
table column defined as
used 260 bytes of storage independent of what was stored
in any particular record. In MySQL 5.1 Cluster tables,
only the portion of the column actually taken up by the
record is stored. This makes possible a significant
reduction in space requirements for such columns as
compared to previous release series—by a factor of
up to 5 in many cases.
Users can define partitions based on columns that are part
of the primary key. It is possible to partition
NDB tables based on
schemes. This feature is also available for many other
MySQL storage engines, which support additional
partitioning types that are not available with
The MySQL Server can also determine whether it is possible
to “prune away” some of the partitions from the
WHERE clause, which can greatly speed up
some queries. See Section 18.4, “Partition Pruning”,
for information about designing tables and queries to take
advantage of partition pruning.
Autodiscovery of table schema changes.
In MySQL 5.0, it was necessary to issue a
TABLES statement or a “dummy”
SELECT for new
NDBCLUSTER tables or changes
made to schemas of existing
NDBCLUSTER tables on one SQL
node to be visible on the cluster's other SQL nodes.
In MySQL 5.1, this is no longer necessary; new Cluster
tables and changes in the definitions of existing
NDBCLUSTER tables made on one
SQL node are immediately visible to all SQL nodes
connected to the cluster.
Distribution awareness (NDB API). Distribution awareness is a mechanism by which the best data node is automatically selected to be queried for information. (Conceptually, it is similar in some ways to partition pruning (see Section 18.4, “Partition Pruning”). To take advantage of distribution awareness, you should do the following:
Determine which table column is most likely to be used for finding matching records.
Make this column part of the table's primary key.
Explicitly partition the table by
KEY, using this column as the
table' partitioning key.
Following these steps causes records with the same value for the partitioning column to be stored on the same partition (that is, in the same node group). When reading data, transactions are begun on the data node actually having the desired rows instead of this node being determined by the usual round-robin mechanism.
To see a measureable impact on performance, the cluster must have at least four data nodes, since, with only two data nodes, both data nodes have exactly the same data.
Using distribution awareness can yield performance increase of as great as 45% when using four data nodes, and possibly more when using a greater number of data nodes.
In mainline MySQL 5.1 releases, distribution awareness was supported only when using the NDB API; support was added for SQL and API nodes in MySQL Cluster NDB 6.3 (see Section 220.127.116.11, “MySQL Cluster Development in MySQL Cluster NDB 6.3”, which includes an example showing how to create a table to take advantage of distribution awareness).
Online adding and dropping of indexes.
ALTER TABLE statements,
ADD INDEX and
INDEX operations for dynamic (variable-width)
NDB tables are now
performed as online operations (no table copying). This is
also true for
DROP INDEX. As a
result, these operations are now performed much more
quickly than previously.
For more information, see
Section 18.104.22.168, “
ALTER TABLE Online Operations in MySQL
Section 13.1.13, “
CREATE INDEX Syntax”, and
Section 13.1.24, “
DROP INDEX Syntax”.
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