Berkeley DB

Logical Join

A logical join is a method of retrieving data from a primary database using criteria stored in a set of secondary indexes. A logical join requires that your data be organized as a primary database, which contains the primary key, the primary data field, and a set of secondary indexes. Each of the secondary indexes is indexed by a different secondary key, and there is a set of duplicate data items that matches the primary keys in the primary database for each key in a secondary index.

For example, let’s assume the need for an application that will return the names of stores in which one can buy fruit of a given color. We would first construct a primary database that lists types of fruit as the key item and the store where you can ...