OData V4 translator

The OData V4 translator, known by the type name "odata4" exposes the OData Version 4 data sources and uses the Teiid web services resource adapter for making web service calls. This translator is extension of Web Services Translator. The OData V4 translator is not for use with older OData V1-3 sources. Use the OData translator ("odata") for older OData sources.

What is OData

The Open Data Protocol (OData) Web protocol is for querying and updating data that provides a way to unlock your data and free it from silos that exist in applications today. OData does this by applying and building upon Web technologies such as HTTP, Atom Publishing Protocol (AtomPub), and JSON to provide access to information from a variety of applications, services, and stores. OData is being used to expose and access information from a variety of sources including, but not limited to, relational databases, file systems, content management systems and traditional Web sites.

Using this specification from the OASIS group, with the help from the Olingo framework, Teiid maps OData V4 CSDL (Conceptual Schema Definition Language) document from the OData endpoint provided and converts the OData metadata into Teiid’s relational schema. The following table shows the mapping selections in the OData V4 translator from a CSDL document

Note
Using OData as a server
Teiid can not only consume OData-based data sources, but it can expose any data source as an OData based web service. For more information see OData Support in the Client Developer’s Guide.
OData Mapped to relational entity

EntitySet

Table

EntityType

Table see [1]

ComplexType

Table see [2]

FunctionImport

Procedure [3]

ActionImport

Procedure [3]

NavigationProperties

Table [4]

[1] Only if the EntityType is exposed as the EntitySet in the Entity container. [2] Only if the complex type is used as property in the exposed EntitySet. This table will be designed as child table with foreign key [1-to-1] or [1-to-many] relationship to the parent.
[3] If the return type is EntityType or ComplexType, the procedure is designed to return a table. [4] Navigation properties are exposed as tables. The table will be created with foreign key relationship to the parent.

All CRUD operations will be appropriately mapped to the resulting entity based on the SQL submitted to the OData translator.

Usage

Usage of a OData source is similar a JDBC translator. The metadata import is supported through the translator, once the metadata is imported from source system and exposed in relational terms, then this source can be queried as if the EntitySets, Function Imports and Action Imports were local to the Teiid system.

It is not recommended to define your own metadata using Teiid DDL for complex services. There are several extension metadata properties required to enable proper functioning. On non-string properties, a NATIVE_TYPE property is expected and should specify the full EDM type name - Edm.xxx.

The below is sample VDB that can read metadata service from TripPin service on http://odata.org site.

<vdb name="trippin" version="1">
    <model name="trippin">
         <source name="odata4" translator-name="odata4" connection-jndi-name="java:/tripDS"/>
    </model>
</vdb>

The required resource-adapter configuration will look like

<resource-adapter id="trippin">
    <module slot="main" id="org.jboss.teiid.resource-adapter.webservice"/>
    <transaction-support>NoTransaction</transaction-support>
    <connection-definitions>
        <connection-definition class-name="org.teiid.resource.adapter.ws.WSManagedConnectionFactory" jndi-name="java:/tripDS" enabled="true" use-java-context="true" pool-name="teiid-trip-ds">
            <config-property name="EndPoint">
                http://services.odata.org/V4/(S(va3tkzikqbtgu1ist44bbft5))/TripPinServiceRW
            </config-property>
        </connection-definition>
    </connection-definitions>
</resource-adapter>

You can connect to the VDB deployed using Teiid JDBC driver and issue SQL statements like

SELECT * FROM trippin.People;
SELECT * FROM trippin.People WHERE UserName = 'russelwhyte';
SELECT * FROM trippin.People p INNER JOIN trippin.People_Friends pf ON p.UserName = pf.People_UserName; (note that People_UserName is implicitly added by Teiid metadata)
EXEC GetNearestAirport(lat, lon) ;
Execution properties

Sometimes default properties need to adjusted for proper execution of the translator. The following execution properties extend or limit the functionality of the translator based on the physical source capabilities.

Name Description Default

SupportsOdataCount

Supports $count

true

SupportsOdataFilter

Supports $filter

true

SupportsOdataOrderBy

Supports $orderby

true

SupportsOdataSkip

Supports $skip

true

SupportsOdataTop

Supports $top

true

SupportsUpdates

Supports INSERT/UPDATE/DELETE

true

The OData server that you connect to might not fully implement the entire OData specification. If the server’s OData implementation does not support a feature, set "execution properties" to turn off the corresponding capability, so that Teiid does not push down invalid queries to the translator.

<translator name="odata-override" type="odata">
     <property name="SupportsOdataFilter" value="false"/>
</translator>

then use "odata-override" as the translator name on your source model.

Importer properties

The following table lists the importer properties that define the behavior of the translator during metadata import from the physical source.

Name Description Default

schemaNamespace

Namespace of the schema to import

null

Example importer settings to only import tables and views from Trippin service exposed on odata.org

<property name="importer.schemaNamespace" value="Microsoft.OData.SampleService.Models.TripPin"/>

You can leave this property undefined. If the translator does not detect a configured instance of the property, it specifies the default name of the EntityContainer.

JCA resource adapter

The resource adapter for this translator is a Web Service Data Source.

Tip
 Native queries - Native or direct query execution is not supported through the OData translator. However, you can use the invokehttp method of the Web services translator to issue REST-based calls, and then use SQLXML to parse results.

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