Github user vasia commented on a diff in the pull request:
https://github.com/apache/flink/pull/818#discussion_r32374715
--- Diff:
flink-staging/flink-gelly/src/main/java/org/apache/flink/graph/Graph.java ---
@@ -1234,6 +1234,18 @@ public void coGroup(Iterable<Edge<K, EV>> edge,
Iterable<Edge<K, EV>> edgeToBeRe
}
/**
+ * Performs Difference on the vertex and edge sets of the input graphs
+ * removes common vertices and edges. If a source/target vertex is
removed, its corresponding edge will also be removed
+ * @param graph the graph to perform difference with
+ * @return a new graph where the common vertices and edges have been
removed
+ */
+ public Graph<K,VV,EV> difference(Graph<K,VV,EV> graph) throws
java.lang.Exception{
+ DataSet<Vertex<K,VV>> removeVerticesData = graph.getVertices();
+ final List<Vertex<K,VV>> removeVerticesList =
removeVerticesData.collect();
--- End diff --
I don't think we should use `collect()` here.. Keep in mind that (1)
`collect()` will trigger program execution and (2) should not be used to
collect large DataSets and input graph might have lots of vertices.
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