A filter join rule defines the relationship between the primary and secondary data views. A filter join rule is configured on the secondary data view by using the filter-join-rule property. This rule indicates how an entry should be retrieved from the secondary data view based on something in the primary data view.
Only one filter join rule can be configured on a secondary data view. If a filter join rule is configured on a data view, a DN join rule cannot be configured on that data view. A filter join rule takes the form of a filter that is used to construct an attribute from one or more attributes from the primary data view.
For example, the following filter join rule stipulates that an entry be retrieved if the entry uid in the primary data view matches the entry uid in the secondary data view.