In this section, we list limits found in MySQL Cluster that either differ from limits found in, or that are not found in, standard MySQL.
Memory usage and recovery.
Memory consumed when data is inserted into an
NDB table is not automatically
recovered when deleted, as it is with other storage engines.
Instead, the following rules hold true:
DELETEstatement on an
NDBtable makes the memory formerly used by the deleted rows available for re-use by inserts on the same table only. However, this memory can be made available for general re-use by performing
A rolling restart of the cluster also frees any memory used by deleted rows. See Section 19.5.5, “Performing a Rolling Restart of a MySQL Cluster”.
Limits imposed by the cluster's configuration. A number of hard limits exist which are configurable, but available main memory in the cluster sets limits. See the complete list of configuration parameters in Section 19.3.3, “MySQL Cluster Configuration Files”. Most configuration parameters can be upgraded online. These hard limits include:
See Section 18.104.22.168, “Defining MySQL Cluster Data Nodes”, for more information.
Different limits related to tables and indexes. For example, the maximum number of ordered indexes in the cluster is determined by
MaxNoOfOrderedIndexes, and the maximum number of ordered indexes per table is 16.
Node and data object maximums. The following limits apply to numbers of cluster nodes and metadata objects:
The maximum number of data nodes is 48.
A data node must have a node ID in the range of 1 to 48, inclusive. (Management and API nodes may use node IDs in the range 1 to 255, inclusive.)
The total maximum number of nodes in a MySQL Cluster is 255. This number includes all SQL nodes (MySQL Servers), API nodes (applications accessing the cluster other than MySQL servers), data nodes, and management servers.
The maximum number of metadata objects in current versions of MySQL Cluster is 20320. This limit is hard-coded.
See Previous MySQL Cluster Issues Resolved in MySQL Cluster NDB 7.3, for more information.