PropertyHandle :: FirstKey - Locate first key

The function locates the first sort key in the index. When the data source is unordered the function locates the first instance and extracts the identifying key. The instance will be located but not positioned.

When a filter or key filter has been set, the function locates the first key or instance fulfilling the filter condition. In case of instance filters, the instance will be positioned.

The returned key area refers to an internal area, which should not be modified by the application. This area is valid until the next ODABA interface function has been called.