Index definition

The index definition defines the order rules for the index of a collection. I ndexes can be defined for local and global collections. The collection should be a typed or weak-typed collection. For untyped collections, only the __IDENTITY index may be defined, which orders the collection by local object identity ( LOID ).

The index definition refers to a key name, which must be a key name defined for the complex data type the collection is based on. Key names that do not require key definitions are __IDENTITY and __UNORDERED . __UNORDERED allows defining user or application defined orders. Each collection may contain only one __UNORDERED index.

Several options can be defined in order to declare case sensitivity, persistence, unique options and others.

Specific index definition is the unordered index. Each collection may get one unordered index, which contains an empty key name. When an unordered index is marked as unique, instances stored within the index must have different primary key values. When no primary key has been defined for the data type, instances stored in the collection must have unique LOID s.