DistinctSourceIds.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.operators.statistics;

import org.apache.flink.api.java.DataSet;
import org.gradoop.flink.model.api.operators.UnaryGraphToValueOperator;
import org.gradoop.flink.model.impl.epgm.LogicalGraph;
import org.gradoop.flink.model.impl.functions.epgm.SourceId;
import org.gradoop.flink.model.impl.operators.count.Count;

/**
 * Computes the number of distinct source vertex ids.
 */
public class DistinctSourceIds implements UnaryGraphToValueOperator<DataSet<Long>> {

  @Override
  public DataSet<Long> execute(LogicalGraph graph) {
    return Count.count(
      graph.getEdges()
        .map(new SourceId<>())
        .distinct()
    );
  }
}