MySQL 8.0 Reference Manual Including MySQL NDB Cluster 8.0
In this section, we list limits found in NDB 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:
A DELETE statement on an
NDB table 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
OPTIMIZE TABLE.
A rolling restart of the cluster also frees any memory used by deleted rows. See Section 25.6.5, “Performing a Rolling Restart of an NDB Cluster”.
A DROP TABLE or
TRUNCATE TABLE operation on
an NDB table frees the memory
that was used by this table for re-use by any
NDB table, either by the same
table or by another NDB table.
Recall that TRUNCATE TABLE
drops and re-creates the table. See
Section 15.1.37, “TRUNCATE TABLE Statement”.
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 25.4.3, “NDB Cluster Configuration Files”. Most configuration parameters can be upgraded online. These hard limits include:
Database memory size and index memory size
(DataMemory and
IndexMemory,
respectively).
DataMemory is
allocated as 32KB pages. As each
DataMemory page
is used, it is assigned to a specific table; once
allocated, this memory cannot be freed except by
dropping the table.
See Section 25.4.3.6, “Defining NDB Cluster Data Nodes”, for more information.
The maximum number of operations that can be performed
per transaction is set using the configuration
parameters
MaxNoOfConcurrentOperations
and
MaxNoOfLocalOperations.
Bulk loading, TRUNCATE
TABLE, and ALTER
TABLE are handled as special cases by
running multiple transactions, and so are not subject
to this limitation.
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 144. (In NDB 7.6 and earlier, this was 48.)
A data node must have a node ID in the range of 1 to 144, inclusive.
Management and API nodes may use node IDs in the range 1 to 255, inclusive.
The total maximum number of nodes in an NDB 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 NDB Cluster is 20320. This limit is hard-coded.
See Section 25.2.7.11, “Previous NDB Cluster Issues Resolved in NDB Cluster 8.0”, for more information.