ElementsOfSelectedGraphs.java

/*
 * Copyright © 2014 - 2021 Leipzig University (Database Research Group)
 *
 * 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 org.gradoop.flink.model.impl.functions.epgm;

import org.apache.flink.api.common.functions.RichFlatMapFunction;
import org.apache.flink.api.java.tuple.Tuple2;
import org.apache.flink.configuration.Configuration;
import org.apache.flink.util.Collector;
import org.gradoop.common.model.api.entities.GraphElement;
import org.gradoop.common.model.impl.id.GradoopId;
import org.gradoop.common.model.impl.id.GradoopIdSet;

/**
 * graphIds (BC)
 * {@code element => (graphId, element),..}
 *
 * \forall (graphId, element) : graphId \in graphIds
 *
 * @param <EL> graph element type
 */
public class ElementsOfSelectedGraphs<EL extends GraphElement>
  extends RichFlatMapFunction<EL, Tuple2<GradoopId, EL>> {

  /**
   * constant string for "graph ids"
   */
  public static final String GRAPH_IDS = "graphIds";

  /**
   * graph ids
   */
  protected GradoopIdSet graphIds;

  /**
   * reuse tuple
   */
  private Tuple2<GradoopId, EL> reuse;

  /**
   * constructor
   */
  public ElementsOfSelectedGraphs() {
    reuse = new Tuple2<>();
  }

  @Override
  public void open(Configuration parameters) throws Exception {
    super.open(parameters);

    graphIds = GradoopIdSet.fromExisting(getRuntimeContext().getBroadcastVariable(GRAPH_IDS));
  }

  @Override
  public void flatMap(EL element, Collector<Tuple2<GradoopId, EL>> collector) throws Exception {
    for (GradoopId graphId : element.getGraphIds()) {
      if (graphIds.contains(graphId)) {
        reuse.f0 = graphId;
        reuse.f1 = element;
        collector.collect(reuse);
      }
    }
  }
}