MySQL :: MySQL Cluster API Developer Guide :: 2.3.24 The NdbRecAttr Class

MySQL Cluster API Developer Guide :: 2 The NDB API :: 2.3 NDB API Classes, Interfaces, and Structures :: 2.3.24 The NdbRecAttr Class

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2.3.24. The `NdbRecAttr` Class

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2.3.24.1. NdbRecAttr Methods

Abstract

The section describes the NdbRecAttr class and its public methods.

Parent class. None

Child classes. None

Description. NdbRecAttr contains the value of an attribute. An NdbRecAttr object is used to store an attribute value after it has been retrieved using the NdbOperation::getValue() method. This object is allocated by the NDB API. A brief example is shown here:

MyRecAttr = MyOperation->getValue("ATTR2", NULL);

if(MyRecAttr == NULL)
  goto error;

if(MyTransaction->execute(Commit) == -1)
  goto error;

ndbout << MyRecAttr->u_32_value();

For additional examples, see Section 2.4.1, “Using Synchronous Transactions”.

Note

An NdbRecAttr object is instantiated with its value only when NdbTransaction::execute() is invoked. Prior to this, the value is undefined. (Use NdbRecAttr::isNULL() to check whether the value is defined.) This means that an NdbRecAttr object has valid information only between the times that NdbTransaction::execute() and Ndb::closeTransaction() are called. The value of the NULL indicator is -1 until the NdbTransaction::execute() method is invoked.

Methods. NdbRecAttr has a number of methods for retrieving values of various simple types directly from an instance of this class.

Note

It is also possible to obtain a reference to the value regardless of its actual type, by using NdbRecAttr::aRef(); however, you should be aware that this is not type-safe, and requires a cast from the user.

The following table lists all of the public methods of this class and the purpose or use of each method:

Method	Purpose / Use
`~NdbRecAttr()`	Destructor method
`aRef()`	Gets a pointer to the attribute value
`char_value()`	Retrieves a `Char` attribute value
`clone()`	Makes a deep copy of the `RecAttr` object
`double_value()`	Retrieves a `Double` attribute value, as a double (8 bytes)
`float_value()`	Retrieves a `Float` attribute value, as a float (4 bytes)
`get_size_in_bytes()`	Gets the size of the attribute, in bytes
`getColumn()`	Gets the column to which the attribute belongs
`getType()`	Gets the attribute's type (`Column::Type`)
`isNULL()`	Tests whether the attribute is `NULL`
`int8_value()`	Retrieves a `Tinyint` attribute value, as an 8-bit integer
`int32_value()`	Retrieves an `Int` attribute value, as a 32-bit integer
`int64_value()`	Retrieves a `Bigint` attribute value, as a 64-bit integer
`medium_value()`	Retrieves a `Mediumint` attribute value, as a 32-bit integer
`short_value()`	Retrieves a `Smallint` attribute value, as a 16-bit integer
`u_8_value()`	Retrieves a `Tinyunsigned` attribute value, as an unsigned 8-bit integer
`u_32_value()`	Retrieves an `Unsigned` attribute value, as an unsigned 32-bit integer
`u_64_value()`	Retrieves a `Bigunsigned` attribute value, as an unsigned 64-bit integer
`u_char_value()`	Retrieves a `Char` attribute value, as an unsigned `char`
`u_medium_value()`	Retrieves a `Mediumunsigned` attribute value, as an unsigned 32-bit integer
`u_short_value()`	Retrieves a `Smallunsigned` attribute value, as an unsigned 16-bit integer

For detailed descriptions, signatures, and examples of use for each of these methods, see Section 2.3.24.1, “NdbRecAttr Methods”.

Types. The NdbRecAttr class defines no public types.

Class diagram. This diagram shows all the available methods of the NdbRecAttr class:

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2.3.24. The NdbRecAttr Class

2.3.24. The `NdbRecAttr` Class