Stream views

Stream views provide flexibility in the use of SdsTypes. While you cannot actually change the properties of SdsTypes themselves, use the stream views feature to create a view of a selected SdsStream that appears as if you had changed the SdsType on which it is based. Create a stream view by choosing a source and target type. Then, create a set of mappings between properties of those two types. Using a stream view to leverage existing SdsType properties is preferable to creating a new SdsType because the SdsStream that is based on the SdsType continues to function with its previously archived stream data intact.

See the impact of the stream view on a stream either in an ad hoc manner through a GET method or by assigning the stream view to a stream with a PUT method.

An SdsStreamView provides a way to map stream data requests from one data type to another. You can apply a stream view to any read or GET operation. SdsStreamView is used to specify the mapping between source and target types.

Stream view fields and properties

The following table shows the SdsStreamView fields. Fields that are not included are reserved for internal Sequential Data Store (SDS (Sequential Data Store)) use. For more information on search limitations, see Search in SDS.

Note: SdsStreamViewProperty objects are not searchable. Only the SdsStreamViewProperty's SdsStreamView is searchable by its Id, SourceTypeId, and TargetTypeId. These are used to return the top level SdsStreamView object when searching. The same is true for nested SdsStreamViewProperties.

Rules for the stream view identifier (SdsStreamView.Id)

The type identifier, SdsStreamView.ID, has the following requirements:

• Is not case sensitive

• Can contain spaces

• Cannot contain forward slash ("/")

• Contains a maximum of 100 characters

SdsStreamView mapping

SDS (Sequential Data Store) attempts to map properties from the source to the destination. When the mapping is straightforward, SDS (Sequential Data Store) automatically maps properties from the source to the target type. For example:

• The properties are in the same position

• The properties are of the same data type

• The properties have the same name

When SDS (Sequential Data Store) is unable to determine how to map a source property, the property is removed. If SDS (Sequential Data Store) encounters a target property that it cannot map to, the property is added and configured with a default value. To map a property that SDS (Sequential Data Store) cannot map automatically, define an SdsStreamViewProperty and add it to the SdsStreamView’s properties.

The following table show mapping compatibilities. SDS (Sequential Data Store) largely supports mapping within the same data type.

* Mappable if typeId matches between the source and the target type

SdsStreamViewProperty

The SdsStreamView properties collection provides detailed instructions for mapping of event properties. Each SdsStreamViewProperty in the properties collection defines the mapping of an event's property. SdsStreamView properties are required only when property mapping is not straightforward. Additionally, if you do not want a type property mapped, it is not necessary to create an SdsStreamView property for it.

The following table shows the required and optional SdsStreamViewProperty fields.

SdsStreamViewMap

When an SdsStreamView is added, SDS (Sequential Data Store) defines a plan mapping and stores it as an SdsStreamViewMap. The SdsStreamViewMap provides a detailed property-by-property definition of the mapping.

The following table shows the SdsStreamViewMap fields. The SdsStreamViewMap cannot be written to SDS (Sequential Data Store), it can only be retrieved from SDS (Sequential Data Store), so required and optional have no meaning.

Properties / SdsStreamViewMapProperty

The SdsStreamViewMapProperty is similar an SdsStreamViewProperty but adds a mode detailing one or more actions taken on the property.

The following table shows the SdsStreamViewMapProperty fields. The SdsStreamViewMap cannot be written to SDS (Sequential Data Store); it can only be retrieved from SDS (Sequential Data Store), so required and optional have no meaning.

The available SdsStreamViewModes are shown in the following table.

Changing stream type

Stream views can be used to change the type defining a stream. You cannot modify the SdsType; types are immutable. But you can map a stream from its current type to a new type.

To update a stream's type, define an SdsStreamView and PUT the stream view to the following:

PUT api/v1/Tenants/default/Namespaces/{namespaceId}/Streams/{streamId}/Type?streamViewId={streamViewId}

For details, see SdsStream API.