1.1.1 MySQL Cluster API Overview: The NDB API

The NDB API is an object-oriented application programming interface for MySQL Cluster that implements indexes, scans, transactions, and event handling. NDB transactions are ACID-compliant in that they provide a means to group operations in such a way that they succeed (commit) or fail as a unit (rollback). It is also possible to perform operations in a no-commit or deferred mode, to be committed at a later time.

NDB scans are conceptually rather similar to the SQL cursors implemented in MySQL 5.0 and other common enterprise-level database management systems. These provide high-speed row processing for record retrieval purposes. (MySQL Cluster naturally supports set processing just as does MySQL in its non-Cluster distributions. This can be accomplished through the usual MySQL APIs discussed in the MySQL Manual and elsewhere.) The NDB API supports both table scans and row scans; the latter can be performed using either unique or ordered indexes. Event detection and handling is discussed in Section 2.3.19, “The NdbEventOperation Class”, as well as Section 2.4.8, “NDB API Event Handling Example”.

In addition, the NDB API provides object-oriented error-handling facilities in order to provide a means of recovering gracefully from failed operations and other problems. (See Section 2.4.3, “Handling Errors and Retrying Transactions”, for a detailed example.)

The NDB API provides a number of classes implementing the functionality described above. The most important of these include the Ndb, Ndb_cluster_connection, NdbTransaction, and NdbOperation classes. These model (respectively) database connections, cluster connections, transactions, and operations. These classes and their subclasses are listed in Section 2.3, “NDB API Classes, Interfaces, and Structures”. Error conditions in the NDB API are handled using NdbError.

Note

NDB API applications access the MySQL Cluster's data store directly, without requiring a MySQL Server as an intermediary. This means that such applications are not bound by the MySQL privilege system; any NDB API application has read and write access to any NDB table stored in the same MySQL Cluster at any time without restriction.

In MySQL Cluster NDB 7.2.0 and later, it is possible to distribute the MySQL grant tables, converting them from the default (MyISAM) storage engine to NDB. Once this has been done, NDB API applications can access any of the MySQL grant tables. This means that such applications can read or write user names, passwords, and any other data stored in these tables.