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:
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. This memory cannot be used
by other NDB
tables.
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 12.2.10, “TRUNCATE TABLE
Syntax”.
Memory freed by DELETE
operations but still allocated to a specific table can also
be made available for general re-use by performing a rolling
restart of the cluster. See
Section 17.2.6.1, “Performing a Rolling Restart of a MySQL Cluster”.
Beginning with MySQL Cluster NDB 6.3.7, this limitation can
be overcome using OPTIMIZE
TABLE
. See
Section 17.1.5.11, “Previous MySQL Cluster Issues Resolved in MySQL 5.1, MySQL Cluster NDB
6.x, and MySQL Cluster NDB 7.x”, for
more information.
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 17.3.2, “MySQL 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 17.3.2.6, “Defining MySQL Cluster Data Nodes”, for
further information about DataMemory
and IndexMemory
.
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 inexes 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. (Previous to MySQL Cluster NDB 6.1.1, management and API nodes were restricted to the range 1 to 63 inclusive as a node ID; starting with MySQL Cluster NDB 6.1.1, management and API nodes may use node IDs in the range 1 to 255, inclusive.)
Prior to MySQL Cluster NDB 6.1.1, the total maximum number of nodes in a MySQL Cluster was 63. Beginning with MySQL Cluster NDB 6.1.1, the total maximum number of nodes in a MySQL Cluster is 255. In either case, 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 Section 17.1.5.11, “Previous MySQL Cluster Issues Resolved in MySQL 5.1, MySQL Cluster NDB 6.x, and MySQL Cluster NDB 7.x”, for more information.
User Comments
Add your own comment.