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    Create Multi-Map Index

    • 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:

    Define a Map Function

    Figure 1. Initial Map Function

    1. Index Name - An index name can be composed of letters, digits, ., /, -, and _. The name must be unique in the scope of the database.

      • Uniqueness is evaluated in a case-insensitive way - you can't create indexes named both usersbyname and UsersByName.
      • The characters _ and / are treated as equivalent - you can't create indexes named both users/byname and users_byname.
      • If the index name contains the character ., it must have some other character on both sides to be valid. /./ is a valid index name, but ./, /., and /../ are all invalid.

    2. The Map Function

    3. 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.

    Add Another Map Function

    Figure 2. Add Another Map Function

    • 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, Configuration, Assitional Assemblies & Additional Sources can be defined for the Multi-Map index in the same way as done for a Simple Map Index.

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