Oracle C++ Call Interface Programmer's Guide

Optimizing Performance
Advanced Relational Techniques
When you provide data for bind parameters by the setxxx methods in
parameterized statements, the values are copied into an internal data buffer, and the
copied values are then provided to the database server for insertion. This data
copying may be expensive, especially if large strings are involved. Also, for each
new value, the string is reallocated, so there may be memory management overhead
in repeated allocation and deallocation of strings.
For these reasons, OCCI provides several methods to help counter these
performance drains. These methods are:
■ setDataBuffer
■ executeArrayUpdate
■ next (of the ResultSet class)
setDataBuffer Method
For high performance applications, OCCI provides the setDataBuffer method
whereby the data buffer is managed by the application. The following example
shows the setDataBuffer method:
void setDataBuffer(int paramIndex,
void *buffer,
Type type,
sb4 size,
ub2 *length,
sb2 *ind = NULL,
ub2 *rc = NULL);
The following parameters are used in the previous method example:
■ paramIndex: Parameter number
■ buffer: Data buffer containing data
■ type: Type of the data in the data buffer
■ size: Size of the data buffer
■ length: Current length of data in the data buffer
■ ind: Indicator information. This indicates whether the data is NULL or not. For
parameterized statements, a value of -1 means a NULL value is to be inserted.
For data returned from callable statements, a value of -1 means NULL data is
retrieved.
Relational Programming 2-27