Oracle 5.0 Reference Manual page 1545

and data using the
requires the same amount of storage as a
• Node and data object maximums.
metadata objects:
• The maximum number of data nodes is 48.
A data node must have a node ID in the range of 1‐49, inclusive. (Management and API nodes
may use any integer in the range of 1‐63 inclusive as a node ID.)
• The total maximum number of nodes in a MySQL Cluster is 63. 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 MySQL 5.0 Cluster is 20320. This limit is hard-
coded.
17.1.5.3. Limits Relating to Transaction Handling in MySQL Cluster
A number of limitations exist in MySQL Cluster with regard to the handling of transactions. These
include the following:
• Transaction isolation level.
READ COMMITTED
READ COMMITTED
SERIALIZABLE
information on how this can affect backing up and restoring Cluster databases.)
• Transactions and
uses any of MySQL's
or
BLOB TEXT
two related issues of which you should be aware whenever executing
that contain columns of these types:
1. For any
the
READ COMMITTED
This is done to guarantee consistency.
2. For any
that use any of the
read lock is held on the table for the duration of the transaction—that is, until the transaction is
either committed or aborted. This does not occur for queries that use index or table scans.
For example, consider the table
CREATE TABLE t (
a INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
b INT NOT NULL,
c INT NOT NULL,
d TEXT,
INDEX i(b),
UNIQUE KEY u(c)
) ENGINE = NDB,
Either of the following queries on
primary key lookup and the second uses a unique key lookup:
SELECT * FROM t WHERE a = 1;
SELECT * FROM t WHERE c = 1;
However, none of the four queries shown here causes a shared read lock:
Known Limitations of MySQL Cluster
engine. (In other words, in the case of a
MyISAM
The
[1121] transaction isolation level. (InnoDB, for example, supports
[1121],
READ UNCOMMITTED
[1121].) See Section 17.5.3.4, "MySQL Cluster Backup
or columns.
BLOB TEXT
or
BLOB TEXT
is stored in a separate internal table that is not accessible to MySQL. This gives rise to
from a MySQL Cluster table: If the
SELECT
[1121] transaction isolation level is converted to a read with read lock.
which uses a primary key lookup or unique key lookup to retrieve any columns
SELECT
or
BLOB TEXT
column of the same size.)
CHAR
The following limits apply to numbers of cluster nodes and
storage engine supports only the
NDBCLUSTER
[1121],
REPEATABLE READ
NDBCLUSTER
data types in the table visible to MySQL; the remainder of the
SELECT
data types and that is executed within a transaction, a shared
defined by the following
t
causes a shared read lock, because the first query uses a
t
1525
column, the column
VARCHAR
[1120], and
Troubleshooting", for
stores only part of a column value that
statements on tables
SELECT
includes a or
BLOB TEXT
statement:
CREATE TABLE
column,