Berkeley DB

DB→key_range

						#include <db.h>
						int
						DB→key_range(DB *db, DB_TXN *txnid,
						DBT *key, DB_KEY_RANGE *key_range, u_int32_t flags);
					

Description

The DB→key_range function returns an estimate of the proportion of keys that are less than, equal to, and greater than the specified key. The underlying database must be of type Btree.

The information is returned in the key_range argument, which contains three elements of type double: less, equal, and greater. Values are in the range of 0 to 1; for example, if the field less is 0.05, 5% of the keys in the database are less than the key argument. The value for equal will be zero if there is no matching key, and will be non-zero otherwise.

If the operation is to be transaction-protected, the txnid parameter is ...