Abstract
This class provides meta-information about database objects, such as tables, columns, and indexes.
While the preferred method of database object creation and
deletion is through the MySQL Server,
NdbDictionary also permits the developer to
perform these tasks through the NDB API.
Parent class. None
Child classes.
Dictionary,
Column,
Object
Description. This is a data dictionary class that supports enquiries about tables, columns, and indexes. It also provides ways to define these database objects and to remove them. Both sorts of functionality are supplied using inner classes that model these objects. These include the following inner classes:
Tablefor working with tablesColumnfor creating table columnsIndexfor working with secondary indexesDictionaryfor creating database objects and making schema enquiriesEventfor working with events in the cluster.
Additional Object subclasses model
the tablespaces, logfile groups, datafiles, and undofiles required
for working with MySQL Cluster Disk Data tables (introduced in MySQL
5.1).
Tables and indexes created using NdbDictionary
cannot be viewed from the MySQL Server.
Dropping indexes through the NDB API that were created originally from a MySQL Cluster causes inconsistencies. It is possible that a table from which one or more indexes have been dropped using the NDB API will no longer be usable by MySQL following such operations. In this event, the table must be dropped, and then re-created using MySQL to make it accessible to MySQL once more.
Methods.
NdbDictionary itself has no public instance
methods, only static methods that are used for working with
NdbRecord objects. Operations not
using NdbRecord are accomplished by means of
NdbDictionary subclass instance methods. The
following table lists the public methods of
NdbDictionary and the purpose or use of each
method:
| Method | Purpose / Use |
|---|---|
getEmptyBitmask() |
Returns an empty column presence bitmask which can be used with
NdbRecord
|
getFirstAttrId() |
Get the first attribute ID specified by a given
NdbRecord object |
getRecordIndexName() |
Gets the name of the index object referred to by an NdbRecord |
getRecordRowLength() |
Get the number of bytes needed to store one row of data using a given
NdbRecord
|
getRecordTableName() |
Gets the name of the table object referred to by an NdbRecord |
getRecordType() |
Gets the RecordType of an NdbRecord |
getValuePtr() |
Returns a pointer to the beginning of stored data specified by attribute
ID, using NdbRecord
|
isNull() |
Show whether the null bit for a column is true or false |
setNull() |
Set a column's null bit |
NdbDictionary Subclass Hierarchy.
This diagram shows the hierarchy made up of the
NdbDictionary class, its subclasses, and their
enumerated data types:
For the numeric equivalents to enumerations of
NdbDictionary subclasses, see the file
/storage/ndb/include/ndbapi/NdbDictionary.hpp
in the MySQL Cluster source tree.
