Berkeley DB

Db::set_bt_prefix

						#include <db_cxx.h>
						extern "C" {
						typedef size_t (*bt_prefix_fcn_type)(DB *, const DBT *, const DBT *);
						};
						int
						Db::set_bt_prefix(bt_prefix_fcn_type bt_prefix_fcn);
					

Description

Set the Btree prefix function. The prefix function must return the number of bytes of the second key argument that would be required by the Btree key comparison function to determine the second key argument’s ordering relationship with respect to the first key argument. If the two keys are equal, the key length should be returned. The prefix function must correctly handle any key values used by the application (possibly including zero-length keys). The data and size fields of the Dbt are the only fields that may be used for the purposes of this determination, ...