A Multi-Map index allows to index data from multiple different collections.
RavenDB will generate a single Multi-Map index.
The results of querying the Multi-Map index will include data from all these collections.
Multi-Map indexes require that all the Map functions defined have the same output structure.
In this page:
Index Name - An index name can be composed of letters, digits, ., /, -, and _. The name must be unique in the scope of the database.
The Map Function
Add another map function to create a multi-map index.
The Collection field indexed in the above example is not mandatory but can be useful upon querying.
Any number of additional Map functions can be added.
Each added Map should have the same output fields.
i.e. In the above example, the common indexed fields are: Name & Collection.
So when querying on this Multi-Map index, results will come from both Employees collection and Companies collection.
Index field options,
& Additional Sources
can be defined for the Multi-Map index in the same way as done for a Simple Map Index.