Output only. A server defined name for this index. The form of this name for composite indexes will be: projects/{projectId}/databases/{databaseId}/collectionGroups/{collectionId}/indexes/{composite_index_id} For single field indexes, this field will be empty.
Indexes with a collection query scope specified allow queries against a collection that is the child of a specific document, specified at query time, and that has the same collection id.
Indexes with a collection group query scope specified allow queries against all collections descended from a specific document, specified at query time, and that have the same collection id as this index.
For composite indexes, this requires a minimum of 2 and a maximum of 100 fields. The last field entry is always for the field path __name__. If, on creation, __name__ was not specified as the last field, it will be added automatically with the same direction as that of the last field defined. If the final field in a composite index is not directional, the __name__ will be ordered ASCENDING (unless explicitly specified).
For single field indexes, this will always be exactly one entry with a field path equal to the field path of the associated field.