DBFieldDef :: get_multikey - MULTIPLE_KEY option

The multiple key option enables the multiple index feature for a collection. When being set, more than one index can be defined for the collection. The option is activated automatically for extent definitions.

The multiple key option enables the multiple index feature for a collection, which allows defining any number of indexes for a collection without creating a new schema version.The option is enabled automatically, as soon as there are at least two access (order) keys defined for the collection. The option should be set in advance for single indexed collection in order to allow creating additional indexes for the collection later on without database reorganization.

The multiple index feature creates an additional access level between the instance and the index of the referenced collection. Hence, this option cannot be changed for an existing database without upgrading the database explicitly (create new schema version).