| /* |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you 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 org.apache.rya.api.function.projection; |
| |
| import static java.util.Objects.requireNonNull; |
| |
| import java.util.HashMap; |
| import java.util.HashSet; |
| import java.util.Map; |
| import java.util.Optional; |
| import java.util.Set; |
| |
| import org.apache.rya.api.model.VisibilityBindingSet; |
| import org.openrdf.model.BNode; |
| import org.openrdf.model.ValueFactory; |
| import org.openrdf.model.impl.ValueFactoryImpl; |
| import org.openrdf.query.algebra.BNodeGenerator; |
| import org.openrdf.query.algebra.Extension; |
| import org.openrdf.query.algebra.ExtensionElem; |
| import org.openrdf.query.algebra.MultiProjection; |
| import org.openrdf.query.algebra.ProjectionElemList; |
| import org.openrdf.query.algebra.TupleExpr; |
| |
| import edu.umd.cs.findbugs.annotations.DefaultAnnotation; |
| import edu.umd.cs.findbugs.annotations.NonNull; |
| |
| /** |
| * Processes a {@link MultiProjection} node from a SPARQL query. |
| * |
| * @see ProjectionEvaluator |
| */ |
| @DefaultAnnotation(NonNull.class) |
| public class MultiProjectionEvaluator { |
| |
| private final ValueFactory vf = new ValueFactoryImpl(); |
| |
| private final Set<ProjectionEvaluator> projections; |
| private final Set<String> blankNodeSourceNames; |
| private final BNodeIdFactory bNodeIdFactory; |
| |
| /** |
| * Constructs an instance of {@link MultiProjection}. |
| * |
| * @param projections - The {@link ProjectionEvaluators} that handle each projection within the MultiProjection. (not null) |
| * @param blankNodeSourceNames - If there are blank nodes in the projection, this is a set of their names |
| * so that they may be re-labeled to have the same node IDs. (not null) |
| * @param bNodeIdFactory - Creates the IDs for Blank Nodes. (not null) |
| */ |
| public MultiProjectionEvaluator( |
| final Set<ProjectionEvaluator> projections, |
| final Set<String> blankNodeSourceNames, |
| final BNodeIdFactory bnodeIdFactory) { |
| this.projections = requireNonNull(projections); |
| this.blankNodeSourceNames = requireNonNull(blankNodeSourceNames); |
| this.bNodeIdFactory = requireNonNull(bnodeIdFactory); |
| } |
| |
| /** |
| * Make a {@link MultiProjectionEvaluator} that processes the logic of a {@link MultiProjection}. |
| * |
| * @param multiProjection - Defines the projections that will be processed. (not null) |
| * @param bNodeIdFactory - Creates the IDs for Blank Nodes. (not null) |
| * @return A {@link MultiProjectionEvaluator} for the provided {@link MultiProjection}. |
| */ |
| public static MultiProjectionEvaluator make(final MultiProjection multiProjection, final BNodeIdFactory bNodeIdFactory) { |
| requireNonNull(multiProjection); |
| |
| // Figure out if there are extensions. |
| final TupleExpr arg = multiProjection.getArg(); |
| final Optional<Extension> extension = (arg instanceof Extension) ? Optional.of((Extension)arg): Optional.empty(); |
| |
| // If there are, iterate through them and find any blank node source names. |
| final Set<String> blankNodeSourceNames = new HashSet<>(); |
| if(extension.isPresent()) { |
| for(final ExtensionElem elem : extension.get().getElements()) { |
| if(elem.getExpr() instanceof BNodeGenerator) { |
| blankNodeSourceNames.add( elem.getName() ); |
| } |
| } |
| } |
| |
| // Create a ProjectionEvaluator for each projection that is part of the multi. |
| final Set<ProjectionEvaluator> projections = new HashSet<>(); |
| for(final ProjectionElemList projectionElemList : multiProjection.getProjections()) { |
| projections.add( new ProjectionEvaluator(projectionElemList, extension) ); |
| } |
| |
| return new MultiProjectionEvaluator(projections, blankNodeSourceNames, bNodeIdFactory); |
| } |
| |
| /** |
| * Apply the projections against a {@link VisibilityBindingSet}. |
| * |
| * @param bs - The value the projection will be applied to. (not null) |
| * @return A set of values that result from the projection. |
| */ |
| public Set<VisibilityBindingSet> project(final VisibilityBindingSet bs) { |
| requireNonNull(bs); |
| |
| // Generate an ID for each blank node that will appear in the results. |
| final Map<String, BNode> blankNodes = new HashMap<>(); |
| for(final String blankNodeSourceName : blankNodeSourceNames) { |
| blankNodes.put(blankNodeSourceName, vf.createBNode(bNodeIdFactory.nextId())); |
| } |
| |
| // Iterate through each of the projections and create the results from them. |
| final Set<VisibilityBindingSet> results = new HashSet<>(); |
| for(final ProjectionEvaluator projection : projections) { |
| results.add( projection.project(bs, blankNodes) ); |
| } |
| |
| return results; |
| } |
| } |