How can a join be combined with a range query?
Imagine an application where a single primary employee database has three fields that are indexed by secondary databases: status, department, salary. The user wishes to query for a specific status, a specific department, and range of salary values. Berkeley DB supports joins, and the join API can be used to select the AND (intersection) of a specific status and a specific department. However, the join API cannot be use to select a range of salaries. Berkeley DB also supports range searches, making it possible to iterate over a range of values using a secondary index such as a salary index. However, there is no way to automatically combine a range search and a join. To combine a range search and a join you’ll need to first perform one of the two using a Berkeley DB API, and then perform the other manually as a “filter” on the results of the first.
