Federated Query Results Retrieval Client

The Federated Query Results Client is a caGrid service client which can retrieve DCQL 2 results and information about the current state of query processing from a Federated Query Processor Service which has been previously issued a query.

The Federated Query Results Client has the same constructors that any standard Introduce generated service client would have, but only those constructors which take an Endpoint Reference Type should be used, since EPRs contain the necessary resource key to access the server-side query results resource.

Typically an instance of the Federated Query Results Retrieval client will be created by the Federated Query Processor client when the queryAsynchronously method is invoked, and no further action should need to be taken to configure the client.

API Methods

The Federated Query Results Retrieval Client supplies standard WS-ResourceLifetime methods, which may be used to set the resource's termination time and immediately dispose of the server side resource. The results client also includes methods supporting WS-Notification, which can be used to determine when various query processing events have happened, and when query results are available.

Other methods specific to the Federated Query Results Client are as follows:

    public boolean isProcessingComplete() throws RemoteException

This method simply returns true if the Federated Query Processor Service has completed execution of the original DCQL 2 query and results are available, or false otherwise.

    public DCQLQueryResultsCollection getResults() throws RemoteException,
        ProcessingNotCompleteFault, FederatedQueryProcessingFault, InternalErrorFault

This method gets the DCQL 2 query results from the resource to which the Federated Query Results Client is connected. If processing has not yet completed (as indicated by the isProcessingComplete method), this will throw a Processing Not Complete Fault. Problems encountered while processing the query will cause a Federated Query Processing Fault to be thrown.

    public CQLQueryResults getAggregateResults() throws RemoteException, 
        FederatedQueryProcessingFault, ProcessingNotCompleteFault, InternalErrorFault

This method behaves very similarly to the Federated Query Engine's executeAndAggregate method. It gets the DCQL query results as a single, aggregate CQL 2 Query Results instance which can be processed further with the standard data service tools.

    public EnumerationResponseContainer enumerate() throws RemoteException, 
        FederatedQueryProcessingFault, ProcessingNotCompleteFault, InternalErrorFault

This method allows a client to make use of WS-Enumeration to retrieve results of DCQL 2 query processing via an Enumeration client.

    public TransferServiceContextReference transfer() throws RemoteException,
        FederatedQueryProcessingFault, ProcessingNotCompleteFault, InternalErrorFault

This method allows a client to use caGrid's Transfer tools to retrieve results of DCQL 2 query processing via the Transfer client tools. This can help with the speed of large result set retrieval.