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Known Limitations of MySQL Cluster
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• Temporary errors.
When first starting a node, it is possible that you may see Error 1204
Temporary failure, distribution changed
and similar temporary errors.
• Errors due to node failure.
The stopping or failure of any data node can result in a number of
different node failure errors. (However, there should be no aborted transactions when performing a
planned shutdown of the cluster.)
In either of these cases, any errors that are generated must be handled within the application. This
should be done by retrying the transaction.
See also
Section 17.1.5.2, “Limits and Differences of MySQL Cluster from Standard MySQL Limits”
.
17.1.5.5. Limits Associated with Database Objects in MySQL Cluster
Some database objects such as tables and indexes have different limitations when using the
NDBCLUSTER
storage engine:
• Identifiers.
Database names, table names and attribute names cannot be as long in
NDB
tables
as when using other table handlers. Attribute names are truncated to 31 characters, and if not unique
after truncation give rise to errors. Database names and table names can total a maximum of 122
characters. In other words, the maximum length for an
NDB
table name is 122 characters, less the
number of characters in the name of the database of which that table is a part.
• Table names containing special characters.
NDB
tables whose names contain characters other
than letters, numbers, dashes, and underscores and which are created on one SQL node may not be
discovered correctly by other SQL nodes. (Bug #31470)
• Number of tables and other database objects.
The maximum number of tables in a Cluster
database in MySQL 5.0 is limited to 1792. The maximum number of all
NDBCLUSTER
database
objects in a single MySQL Cluster—including databases, tables, and indexes—is limited to 20320.
• Attributes per table.
The maximum number of attributes (that is, columns and indexes) per table
is limited to 128.
• Attributes per key.
The maximum number of attributes per key is 32.
• Row size.
The maximum permitted size of any one row is 8052 bytes. Each
BLOB
or
TEXT
column contributes 256 + 8 = 264 bytes to this total.
• Number of rows per partition.
The maximum number of rows that can be stored in a single
MySQL Cluster partition varies with the number of replicas times the number of fragments. Since
the number of partitions is the same as the number of data nodes in the cluster (see
Section 17.1.2,
“MySQL Cluster Nodes, Node Groups, Replicas, and Partitions”
), you can increase the number of
fragments—and thus the available space—by using more data nodes.
17.1.5.6. Unsupported or Missing Features in MySQL Cluster
A number of features supported by other storage engines are not supported for
NDB
tables. Trying to
use any of these features in MySQL Cluster does not cause errors in or of itself; however, errors may
occur in applications that expects the features to be supported or enforced:
• Foreign key constraints.
The foreign key construct is ignored, just as it is in
MyISAM
tables.
• Index prefixes.
Prefixes on indexes are not supported for
NDBCLUSTER
tables. If a prefix is used
as part of an index specification in a statement such as
CREATE TABLE
,
ALTER TABLE
, or
CREATE
INDEX
, the prefix is ignored.
•
OPTIMIZE
operations.
OPTIMIZE
operations are not supported.
•
LOAD TABLE ... FROM MASTER
.
LOAD TABLE ... FROM MASTER
is not supported.
• Savepoints and rollbacks.
Savepoints and rollbacks to savepoints are ignored as in
MyISAM
.
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