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:
SPARQLFederatedService
public class RepositoryFederatedService extends Object implements FederatedService
Federated Service wrapping the Repository to communicate with a SPARQL endpoint.
Author:
Andreas Schwarte

  • Field Details

    • 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 Details

    • 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 Details

    • select

      public CloseableIteration<BindingSet> 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
      baseUri -
      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
      baseUri -
      Returns:
      true if at least one result exists
      Throws:
      QueryEvaluationException - If there was an exception generated while evaluating the query.

    • evaluate

      public CloseableIteration<BindingSet> evaluate(Service service, CloseableIteration<BindingSet> 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

      invalid reference 
      org.eclipse.rdf4j.query.algebra.evaluation.federation.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> evaluateInternal(Service service, CloseableIteration<BindingSet> 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