org.eclipse.rdf4j.query

Class QueryResults

java.lang.Object

org.eclipse.rdf4j.common.iteration.Iterations

org.eclipse.rdf4j.query.QueryResults

Direct Known Subclasses:

QueryResultUtil

public class QueryResults
extends Iterations

Utility methods related to query results.

Author:

Jeen Broekstra

Constructor Summary

Constructors

Constructor and Description
QueryResults()

Method Summary

Modifier and Type	Method and Description
static Model	asModel(CloseableIteration<? extends Statement,? extends RDF4JException> iteration) Get a Model containing all elements obtained from the specified query result.
static boolean	bindingSetsCompatible(BindingSet bs1, BindingSet bs2) Check whether two BindingSets are compatible.
static GraphQueryResult	distinctResults(GraphQueryResult queryResult) Returns a GraphQueryResult that filters out any duplicate solutions from the supplied queryResult.
static TupleQueryResult	distinctResults(TupleQueryResult queryResult) Returns a TupleQueryResult that filters out any duplicate solutions from the supplied queryResult.
static boolean	equals(GraphQueryResult result1, GraphQueryResult result2) Compares two graph query results and returns true if they are equal.
static boolean	equals(TupleQueryResult tqr1, TupleQueryResult tqr2) Compares two tuple query results and returns true if they are equal.
static boolean	isSubset(TupleQueryResult tqr1, TupleQueryResult tqr2)
static GraphQueryResult	limitResults(GraphQueryResult queryResult, long limit, long offset) Returns a GraphQueryResult that returns at most the specified maximum number of solutions, starting at the supplied offset.
static TupleQueryResult	limitResults(TupleQueryResult queryResult, long limit, long offset) Returns a TupleQueryResult that returns at most the specified maximum number of solutions, starting at the supplied offset.
static GraphQueryResult	parseGraphBackground(InputStream in, String baseURI, RDFFormat format) Parses an RDF document and returns it as a GraphQueryResult object, with parsing done on a separate thread in the background. IMPORTANT: As this method will spawn a new thread in the background, it is vitally important that the resulting GraphQueryResult be closed consistently when it is no longer required, to prevent resource leaks.
static void	report(GraphQueryResult gqr, RDFHandler rdfHandler) Reports a graph query result to an RDFHandler.
static void	report(TupleQueryResult tqr, QueryResultHandler handler) Reports a tuple query result to a TupleQueryResultHandler.
static Statement	singleResult(GraphQueryResult result) Returns a single element from the query result.
static BindingSet	singleResult(TupleQueryResult result) Returns a single element from the query result.

Methods inherited from class org.eclipse.rdf4j.common.iteration.Iterations

addAll, asList, asSet, closeCloseable, stream, toString, toString

Methods inherited from class java.lang.Object

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

Constructor Detail

QueryResults

public QueryResults()

Method Detail

asModel

public static Model asModel(CloseableIteration<? extends Statement,? extends RDF4JException> iteration)
                     throws QueryEvaluationException

Get a Model containing all elements obtained from the specified query result.

Parameters:

iteration - the source iteration to get the statements from. This can be a GraphQueryResult, a RepositoryResult<Statement>, or any other instance of <Statement>

Returns:

a Model containing all statements obtained from the specified source iteration.

Throws:

QueryEvaluationException

singleResult

public static Statement singleResult(GraphQueryResult result)
                              throws QueryEvaluationException

Returns a single element from the query result. The QueryResult is automatically closed by this method.

Returns:

a single query result element.

Throws:

QueryEvaluationException

singleResult

public static BindingSet singleResult(TupleQueryResult result)
                               throws QueryEvaluationException

Returns a single element from the query result. The QueryResult is automatically closed by this method.

Returns:

a single query result element.

Throws:

QueryEvaluationException

distinctResults

public static GraphQueryResult distinctResults(GraphQueryResult queryResult)

Returns a GraphQueryResult that filters out any duplicate solutions from the supplied queryResult.

Parameters:

queryResult - a queryResult containing possible duplicate statements.

Returns:

a GraphQueryResult with any duplicates filtered out.

distinctResults

public static TupleQueryResult distinctResults(TupleQueryResult queryResult)

Returns a TupleQueryResult that filters out any duplicate solutions from the supplied queryResult.

Parameters:

queryResult - a queryResult containing possible duplicate solutions.

Returns:

a TupleQueryResult with any duplicates filtered out.

limitResults

public static TupleQueryResult limitResults(TupleQueryResult queryResult,
                                            long limit,
                                            long offset)

Returns a TupleQueryResult that returns at most the specified maximum number of solutions, starting at the supplied offset.

Parameters:

queryResult - a query result possibly containing more solutions than the specified maximum.

limit - the maximum number of solutions to return. If set to 0 or lower, no limit will be applied.

offset - the number of solutions to skip at the beginning. If set to 0 or lower, no offset will be applied.

Returns:

A TupleQueryResult that will at return at most the specified maximum number of solutions. If neither limit nor offset are applied, this returns the original queryResult.

limitResults

public static GraphQueryResult limitResults(GraphQueryResult queryResult,
                                            long limit,
                                            long offset)

Returns a GraphQueryResult that returns at most the specified maximum number of solutions, starting at the supplied offset.

Parameters:

queryResult - a query result possibly containing more solutions than the specified maximum.

limit - the maximum number of solutions to return. If set to 0 or lower, no limit will be applied.

offset - the number of solutions to skip at the beginning. If set to 0 or lower, no offset will be applied.

Returns:

A GraphQueryResult that will at return at most the specified maximum number of solutions. If neither limit nor offset are applied, this returns the original queryResult.

parseGraphBackground

public static GraphQueryResult parseGraphBackground(InputStream in,
                                                    String baseURI,
                                                    RDFFormat format)
                                             throws UnsupportedRDFormatException

Parses an RDF document and returns it as a GraphQueryResult object, with parsing done on a separate thread in the background.
IMPORTANT: As this method will spawn a new thread in the background, it is vitally important that the resulting GraphQueryResult be closed consistently when it is no longer required, to prevent resource leaks.

Parameters:

in - The InputStream containing the RDF document.

baseURI - The base URI for the RDF document.

format - The RDFFormat of the RDF document.

Returns:

A GraphQueryResult that parses in the background, and must be closed to prevent resource leaks.

Throws:

UnsupportedRDFormatException

report

public static void report(TupleQueryResult tqr,
                          QueryResultHandler handler)
                   throws TupleQueryResultHandlerException,
                          QueryEvaluationException

Reports a tuple query result to a TupleQueryResultHandler.
The CloseableIteration.close() method will always be called before this method returns.
If there is an exception generated by the TupleQueryResult, QueryResultHandler.endQueryResult() will not be called.

Parameters:

tqr - The query result to report.

handler - The handler to report the query result to.

Throws:

TupleQueryResultHandlerException - If such an exception is thrown by the used query result writer.

QueryEvaluationException

report

public static void report(GraphQueryResult gqr,
                          RDFHandler rdfHandler)
                   throws RDFHandlerException,
                          QueryEvaluationException

Reports a graph query result to an RDFHandler.
The CloseableIteration.close() method will always be called before this method returns.
If there is an exception generated by the GraphQueryResult, RDFHandler.endRDF() will not be called.

Parameters:

gqr - The query result to report.

rdfHandler - The handler to report the query result to.

Throws:

RDFHandlerException - If such an exception is thrown by the used RDF writer.

QueryEvaluationException

equals

public static boolean equals(TupleQueryResult tqr1,
                             TupleQueryResult tqr2)
                      throws QueryEvaluationException

Compares two tuple query results and returns true if they are equal. Tuple query results are equal if they contain the same set of BindingSets and have the same headers. Blank nodes identifiers are not relevant for equality, they are matched by trying to find compatible mappings between BindingSets. Note that the method consumes both query results fully.

Parameters:

tqr1 - the first TupleQueryResult to compare.

tqr2 - the second TupleQueryResult to compare.

Throws:

QueryEvaluationException

isSubset

public static boolean isSubset(TupleQueryResult tqr1,
                               TupleQueryResult tqr2)
                        throws QueryEvaluationException

Throws:

QueryEvaluationException

equals

public static boolean equals(GraphQueryResult result1,
                             GraphQueryResult result2)
                      throws QueryEvaluationException

Compares two graph query results and returns true if they are equal. Two graph query results are considered equal if they are isomorphic graphs. Note that the method consumes both query results fully.

Parameters:

result1 - the first query result to compare

result2 - the second query result to compare.

Returns:

true iff the supplied graph query results are isomorphic graphs, false otherwise.

Throws:

QueryEvaluationException

See Also:

Models#isomorphic(Iterable, Iterable)}

bindingSetsCompatible

public static boolean bindingSetsCompatible(BindingSet bs1,
                                            BindingSet bs2)

Check whether two BindingSets are compatible. Two binding sets are compatible if they have equal values for each binding name that occurs in both binding sets.