VertexLabeledEdgeListDataSource.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.io.impl.edgelist;

import org.apache.flink.api.java.DataSet;
import org.apache.flink.api.java.ExecutionEnvironment;
import org.apache.flink.api.java.tuple.Tuple2;
import org.apache.flink.api.java.tuple.Tuple4;
import org.apache.flink.api.java.utils.DataSetUtils;
import org.gradoop.flink.io.impl.edgelist.functions.CreateImportEdge;
import org.gradoop.flink.io.impl.edgelist.functions.CreateLabeledImportVertex;
import org.gradoop.flink.io.impl.graph.GraphDataSource;
import org.gradoop.flink.io.impl.graph.tuples.ImportEdge;
import org.gradoop.flink.io.impl.graph.tuples.ImportVertex;
import org.gradoop.flink.model.impl.epgm.GraphCollection;
import org.gradoop.flink.model.impl.epgm.LogicalGraph;
import org.gradoop.flink.model.impl.operators.combination.ReduceCombination;
import org.gradoop.flink.util.GradoopFlinkConfig;

import java.io.IOException;

/**
 * Data source to create a {@link LogicalGraph} from an edge list. Vertices are annotated with a
 * string label/value, e.g.
 *
 * 0 EN 1 ZH
 * 2 DE 0 EN
 *
 * The example line denotes an edge between two vertices:
 * First edge:
 * source: with id = 0 and vertex value "EN" and
 * target: with id = 1 and vertex value "ZH".
 *
 * Second edge:
 * source: with id = 2 and vertex value "DE" and
 * target: with id = 0 and vertex value "EN".
 *
 * This data source implementation will create a logical graph based on the specified edge list. The
 * resulting vertices will have a user-defined property that stores the label/value. The type of
 * that value will be string.
 */
public class VertexLabeledEdgeListDataSource extends EdgeListDataSource {
  /**
   * property key which should be used for storing the property information
   */
  private String propertyKey;

  /**
   * Creates a new data source. Paths can be local (file://) or HDFS (hdfs://).
   *
   * @param edgeListPath    Path to edge list file
   * @param tokenSeparator  Separator token
   * @param propertyKey     Property key for storing the vertex value
   * @param config          Gradoop Flink configuration
   */
  public VertexLabeledEdgeListDataSource(String edgeListPath, String tokenSeparator,
    String propertyKey,
    GradoopFlinkConfig config) {
    super(edgeListPath, tokenSeparator, config);
    this.propertyKey = propertyKey;
  }


  @Override
  public LogicalGraph getLogicalGraph() throws IOException {
    return getGraphCollection().reduce(new ReduceCombination<>());
  }

  @Override
  public GraphCollection getGraphCollection() throws IOException {

    ExecutionEnvironment env = getConfig().getExecutionEnvironment();

    //--------------------------------------------------------------------------
    // generate tuple that contains all information
    //--------------------------------------------------------------------------

    DataSet<Tuple4<Long, String, Long, String>> lineTuples = env
      .readCsvFile(getEdgeListPath())
      .fieldDelimiter(getTokenSeparator())
      .types(Long.class, String.class, Long.class, String.class);

    //--------------------------------------------------------------------------
    // generate vertices
    //--------------------------------------------------------------------------

    DataSet<ImportVertex<Long>> importVertices = lineTuples
      .<Tuple2<Long, String>>project(0, 1)
      .union(lineTuples.project(2, 3))
      .distinct(0)
      .map(new CreateLabeledImportVertex<>(propertyKey));

    //--------------------------------------------------------------------------
    // generate edges
    //--------------------------------------------------------------------------

    DataSet<ImportEdge<Long>> importEdges = DataSetUtils
      .zipWithUniqueId(lineTuples.<Tuple2<Long, Long>>project(0, 2))
      .map(new CreateImportEdge<>());

    //--------------------------------------------------------------------------
    // create graph data source
    //--------------------------------------------------------------------------

    return new GraphDataSource<>(importVertices, importEdges, getConfig())
      .getGraphCollection();
  }
}