Configuration Features

This section describes the way date-and-time values and numeric values are handled. It also discusses the array modes whereby Rogue Wave DB Link sends or fetches several rows at a time. The following items are described:

Date-and-time related values can be sent and retrieved as strings. This entails a dependence on the RDBMS configuration parameters and LOCALE settings. The behavior with date-and-time column data types can be changed. The default behavior ensures compatibility with older versions, but the new behavior allows you to use objects to handle date-and-time values.

To turn off the default behavior for all IldRequest objects created from a specific IldDbms object or to set a specific IldRequest object to handle date-and-time related values as objects, use the member function IldIldBase::setStringDateUse, with its argument set to IlFalse.

To find the current setting, use the member function IldIldBase::useStringDate, which returns a Boolean value.

The error ILD_TYPE_MISMATCH is raised when an application tries to send or retrieve a date-and-time value as an object when the date as string feature is turned on. Likewise, the same error is raised if an application tries to send or retrieve a date-and-time value as a string —instead of as an object—when the date as string feature is turned off.

Numeric data values (and decimal values when applicable) can be sent and retrieved as double values. However, this causes a loss in precision. The behavior with respect to exact numeric column data types can be changed.

The default behavior ensures compatibility with older versions, but you can change it to preserve exact precision for very large numbers by handling these values as strings.

To turn off the default behavior for all IldRequest objects created from a specific IldDbms object or to set a specific IldRequest object to handle numeric values as strings, use the member function IldIldBase::setStringNumericUse with its argument set to IlTrue. To handle numeric values as numeric objects, use the member function with its argument set to IlFalse, as shown below:

To find the current setting, use the member function IldIldBase::useStringNumeric. It returns a Boolean value.

Both member functions are inherited from the common base class IldIldBase. No error is raised if an application retrieves a numeric value as double when the numeric as string feature is turned on, but the returned value is irrelevant.

It is possible to bind a database numeric type variable as an Rogue Wave DB Link string variable. The conversion is handled silently.

The numeric as string feature has a drawback: since the application depends upon the current LOCALE, the fractional-part and thousands separators may change from one session to another.

To avoid that external dependency, Rogue Wave DB Link allows you to send and retrieve numeric and decimal values under object form. The class IlNumeric is intended for that purpose.

To turn off the default behavior for all IldRequest objects created from a specific IldDbms object or to set a specific IldRequest object to handle numeric values as objects, use the member function IldIldBase::setNumericUse with its argument set to IlTrue.

To find the current setting, use the member function IldIldBase::useNumeric, which returns a Boolean value.

To retrieve the numeric value of a select-list column in object form, use the function IldRequest::getColNumericValue. The error ILD_TYPE_MISMATCH is raised when this function is used and the numeric as object feature has not been turned on. Conversely, it is also an error to try to retrieve the value in string form if the feature is turned on.

A parameter value can be set using the function IldRequest::setParamValue and retrieved by means of the function IldRequest::getParamNumericValue.

Array bind means that Rogue Wave DB Link sends several rows of parameter values each time a prepared query is executed.

To set the array bind mode, pass the number of rows you want to be sent at a time.

This number can be set as a default value for all IldRequest objects requested from one IldDbms object but it can be changed for any particular instance of IldRequest whenever needed.

To set the default value for all newly created IldRequest objects, use the member function IldDbms::setDefaultParamArraySize, passing it a positive integer value as its argument. The new value is set to all cursors requested after that setting, but it is not changed for cursors already held by the application. The current default array bind size can be retrieved using the function IldDbms::getDefaultParamArraySize.

For each IldRequest object, you can change the array size using the function IldRequest::setParamArraySize with a positive integer as its argument. To be effective, this setting must take place before the call to IldRequest::parse or IldRequest::execute.

To get the array size, use IldRequest::getParamArraySize and to reset it, use IldRequest::removeParamArraySize.

For RDBMS whose API does not support this feature, Rogue Wave DB Link emulates it. This is the case of Informix, which supports the array bind mode only for insert statements within a transaction.

Array fetch means that Rogue Wave DB Link fetches several rows at a time from the current result set and buffer the returned values. This optimizes network traffic by reducing the number of messages exchanged between the client application and the database server.

To set the default value for all IldRequest objects requested from an IldDbms object, use the function IldDbms::setDefaultColArraySize with a positive integer as its argument. The cursors already held by the application are not affected by the setting.

For each IldRequest object, this setting can be changed using the member function IldRequest::setColArraySize with a positive integer as its argument, or reset using IldRequest::removeColArraySize. To be effective, the setting must take place before the first call to fetch.

To get the current array size, use IldRequest::getColArraySize.

With ODBC, the array fetch feature is available only if the driver has level 2 compliance.

For RDBMS whose API does not support this feature, Rogue Wave DB Link emulates it, but with no optimization effect on the network load.