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Connector kit for RDF4J-based SPARQL repositories.

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/*
 * Copyright © 2013-2022 Metreeca srl
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.metreeca.rdf4j.actions;

import com.metreeca.rdf4j.services.Graph;
import com.metreeca.rest.services.Logger;

import org.eclipse.rdf4j.query.BindingSet;
import org.eclipse.rdf4j.query.Operation;

import java.util.function.Function;
import java.util.stream.Stream;

import static com.metreeca.rest.Toolbox.service;
import static com.metreeca.rest.services.Logger.time;

import static org.eclipse.rdf4j.common.iteration.Iterations.asList;
import static org.eclipse.rdf4j.query.QueryLanguage.SPARQL;

import static java.lang.String.format;

/**
 * SPARQL tuple query action.
 *
 * Executes SPARQL tuple queries against the {@linkplain #graph(Graph) target graph}.
 */
public final class TupleQuery extends Action implements Function> {

	private final Logger logger=service(Logger.logger());


	/**
	 * Executes a SPARQL tuple query.
	 *
	 * @param query the graph query to be executed
	 *
	 * @return a stream of binding sets produced by executing {@code query} against the {@linkplain #graph(Graph)
	 * target graph} after {@linkplain #configure(Operation) configuring} it; null or empty queries are silently ignored
	 */
	@Override public Stream apply(final String query) {
		return query == null || query.isEmpty() ? Stream.empty() : graph().query(connection -> time(() ->

				asList(configure(connection.prepareTupleQuery(SPARQL, query, base())).evaluate()).parallelStream()

		).apply((t, v) ->

				logger.info(this, format("executed in <%,d> ms", t))

		));
	}

}