Package org.eclipse.rdf4j.repository.sparql.federation

Class RepositoryFederatedService

java.lang.Object

org.eclipse.rdf4j.repository.sparql.federation.RepositoryFederatedService

All Implemented Interfaces:

FederatedService

Direct Known Subclasses:

RepositoryFederatedService, SPARQLFederatedService

public class RepositoryFederatedService
extends Object
implements FederatedService

Federated Service wrapping the Repository to communicate with a SPARQL endpoint.

Author:

Andreas Schwarte

Field Summary

Fields

Modifier and Type	Field	Description
protected int	boundJoinBlockSize	The number of bindings sent in a single subquery in evaluate(Service, CloseableIteration, String) If blockSize is set to 0, the entire input stream is used as block input the block size effectively determines the number of remote requests
protected boolean	shutDown

Constructor Summary

Constructors

Constructor	Description
RepositoryFederatedService(Repository repo)
RepositoryFederatedService(Repository repo, boolean shutDown)

Method Summary

Modifier and Type	Method	Description
boolean	ask(Service service, BindingSet bindings, String baseUri)	Evaluate the provided sparqlQueryString at the initialized Repository of this FederatedService.
CloseableIteration<BindingSet,QueryEvaluationException>	evaluate(Service service, CloseableIteration<BindingSet,QueryEvaluationException> bindings, String baseUri)	Evaluate the provided SPARQL query at this federated service, possibilities for vectored evaluation.
protected CloseableIteration<BindingSet,QueryEvaluationException>	evaluateInternal(Service service, CloseableIteration<BindingSet,QueryEvaluationException> bindings, String baseUri)	Evaluate the SPARQL query that can be constructed from the SERVICE node at the initialized Repository of this FederatedService.
int	getBoundJoinBlockSize()
protected RepositoryConnection	getConnection()	Retrieve a (re-usable) connection.
void	initialize()	Method to perform any initializations, invoked after construction.
protected String	insertValuesClause(String queryString, String valuesClause)	Insert the constructed VALUES clause in the beginning of the WHERE block.
boolean	isInitialized()	Method to check if FederatedService.initialize() had been called.
CloseableIteration<BindingSet,QueryEvaluationException>	select(Service service, Set<String> projectionVars, BindingSet bindings, String baseUri)	Evaluate the provided sparqlQueryString at the initialized Repository of this FederatedService.
void	setBoundJoinBlockSize(int boundJoinBlockSize)
void	setUseFreshConnection(boolean flag)
void	shutdown()	Method to perform any shutDown code, invoked at unregistering.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

boundJoinBlockSize

protected int boundJoinBlockSize

The number of bindings sent in a single subquery in evaluate(Service, CloseableIteration, String) If blockSize is set to 0, the entire input stream is used as block input the block size effectively determines the number of remote requests

shutDown

protected boolean shutDown

Constructor Detail

RepositoryFederatedService

public RepositoryFederatedService(Repository repo)

Parameters:

repo - the repository to be used

RepositoryFederatedService

public RepositoryFederatedService(Repository repo,
                                  boolean shutDown)

Parameters:

repo - the repository to be used

shutDown - a flag indicating whether the repository shall be closed in shutdown()

Method Detail

select

public CloseableIteration<BindingSet,QueryEvaluationException> select(Service service,
                                                                            Set<String> projectionVars,
                                                                            BindingSet bindings,
                                                                            String baseUri)
                                                                     throws QueryEvaluationException

Evaluate the provided sparqlQueryString at the initialized Repository of this FederatedService. Insert bindings into SELECT query and evaluate

Specified by:

select in interface FederatedService

Parameters:

service - the reference to the service node, contains additional meta information (vars, prefixes)

projectionVars - The variables with unknown value that should be projected from this evaluation

bindings - the bindings serving as additional constraints

Returns:

an iteration over the results of the query

Throws:

QueryEvaluationException - If there was an exception generated while evaluating the query.

ask

public boolean ask(Service service,
                   BindingSet bindings,
                   String baseUri)
            throws QueryEvaluationException

Evaluate the provided sparqlQueryString at the initialized Repository of this FederatedService. Insert bindings, send ask query and return final result

Specified by:

ask in interface FederatedService

Parameters:

service - the reference to the service node, contains additional meta information (vars, prefixes)

bindings - the bindings serving as additional constraints

Returns:

true if at least one result exists

Throws:

QueryEvaluationException - If there was an exception generated while evaluating the query.

evaluate

public CloseableIteration<BindingSet,QueryEvaluationException> evaluate(Service service,
                                                                              CloseableIteration<BindingSet,QueryEvaluationException> bindings,
                                                                              String baseUri)
                                                                       throws QueryEvaluationException

Description copied from interface: FederatedService

Evaluate the provided SPARQL query at this federated service, possibilities for vectored evaluation.

Contracts:

• The original bindings need to be inserted into the result
• SILENT service must be dealt with in the method

Compare SPARQLFederatedService for a reference implementation

Specified by:

evaluate in interface FederatedService

Parameters:

service - the reference to the service node, contains information to construct the query

bindings - the bindings serving as additional constraints (for vectored evaluation)

baseUri - the baseUri

Returns:

the result of evaluating the query using bindings as constraints, the original bindings need to be inserted into the results!

Throws:

QueryEvaluationException - If there was an exception generated while evaluating the query.

evaluateInternal

protected CloseableIteration<BindingSet,QueryEvaluationException> evaluateInternal(Service service,
                                                                                         CloseableIteration<BindingSet,QueryEvaluationException> bindings,
                                                                                         String baseUri)
                                                                                  throws QueryEvaluationException

Evaluate the SPARQL query that can be constructed from the SERVICE node at the initialized Repository of this FederatedService. Use specified bindings as constraints to the query. Try to evaluate using VALUES clause, if this yields an exception fall back to the naive implementation. This method deals with SILENT SERVICEs.

Throws:

QueryEvaluationException

insertValuesClause

protected String insertValuesClause(String queryString,
                                    String valuesClause)

Insert the constructed VALUES clause in the beginning of the WHERE block. Also adds the ROW_IDX_VAR projection if it is not already present.

Parameters:

queryString - the SELECT query string from the SERVICE node

valuesClause - the constructed VALUES clause

Returns:

the final String

initialize

public void initialize()
                throws QueryEvaluationException

Description copied from interface: FederatedService

Method to perform any initializations, invoked after construction.

Specified by:

initialize in interface FederatedService

Throws:

QueryEvaluationException - If there was an exception generated while initializing the service.

isInitialized

public boolean isInitialized()

Description copied from interface: FederatedService

Method to check if FederatedService.initialize() had been called.

Specified by:

isInitialized in interface FederatedService

getBoundJoinBlockSize

public int getBoundJoinBlockSize()

setBoundJoinBlockSize

public void setBoundJoinBlockSize(int boundJoinBlockSize)

Parameters:

boundJoinBlockSize - the bound join block size, 0 to evaluate all in a single request

setUseFreshConnection

public void setUseFreshConnection(boolean flag)

Parameters:

flag - whether to use a fresh RepositoryConnection for each individual query

shutdown

public void shutdown()
              throws QueryEvaluationException

Description copied from interface: FederatedService

Method to perform any shutDown code, invoked at unregistering.

Specified by:

shutdown in interface FederatedService

Throws:

QueryEvaluationException - If there was an exception generated while shutting down the service.

getConnection

protected RepositoryConnection getConnection()
                                      throws RepositoryException

Retrieve a (re-usable) connection. If it is not yet created, open a fresh connection. Note that this connection is closed automatically when shutting this service.

Returns:

connection

Throws:

RepositoryException