Github user greghogan commented on a diff in the pull request: https://github.com/apache/flink/pull/2021#discussion_r64594890 --- Diff: flink-libraries/flink-gelly/src/main/java/org/apache/flink/graph/asm/degree/annotate/directed/EdgeDegreesPair.java --- @@ -0,0 +1,81 @@ +/* + * 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.flink.graph.asm.degree.annotate.directed; + +import org.apache.flink.api.common.ExecutionConfig; +import org.apache.flink.api.common.operators.base.JoinOperatorBase.JoinHint; +import org.apache.flink.api.java.DataSet; +import org.apache.flink.api.java.tuple.Tuple2; +import org.apache.flink.api.java.tuple.Tuple3; +import org.apache.flink.graph.Edge; +import org.apache.flink.graph.Graph; +import org.apache.flink.graph.GraphAlgorithm; +import org.apache.flink.graph.Vertex; +import org.apache.flink.graph.asm.degree.annotate.DegreeAnnotationFunctions.JoinEdgeDegreeWithVertexDegree; +import org.apache.flink.graph.asm.degree.annotate.directed.VertexDegrees.Degrees; + +/** + * Annotates edges of a directed graph with the degree, out-degree, and + * in-degree of both the source and target vertices. + * + * @param <K> ID type + * @param <VV> vertex value type + * @param <EV> edge value type + */ +public class EdgeDegreesPair<K, VV, EV> +implements GraphAlgorithm<K, VV, EV, DataSet<Edge<K, Tuple3<EV, Degrees, Degrees>>>> { + + // Optional configuration + private int parallelism = ExecutionConfig.PARALLELISM_UNKNOWN; + + /** + * Override the operator parallelism. + * + * @param parallelism operator parallelism + * @return this + */ + public EdgeDegreesPair<K, VV, EV> setParallelism(int parallelism) { + this.parallelism = parallelism; + + return this; + } + + @Override + public DataSet<Edge<K, Tuple3<EV, Degrees, Degrees>>> run(Graph<K, VV, EV> input) + throws Exception { + // s, t, d(s) + DataSet<Edge<K, Tuple2<EV, Degrees>>> edgeSourceDegrees = input + .run(new EdgeSourceDegrees<K, VV, EV>() + .setParallelism(parallelism)); + + // t, d(t) + DataSet<Vertex<K, Degrees>> vertexDegrees = input + .run(new VertexDegrees<K, VV, EV>() + .setParallelism(parallelism)); + + // s, t, (d(s), d(t)) + return edgeSourceDegrees + .join(vertexDegrees, JoinHint.REPARTITION_HASH_SECOND) --- End diff -- I'm amenable to adding this configuration if we can show noticeably improved performance. Choosing a bad `JoinHint` will result in significantly degraded performance for most graphs in addition to adding to the user's cognitive load.
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