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https://issues.apache.org/jira/browse/FLINK-10566?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16714970#comment-16714970
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Maximilian Michels commented on FLINK-10566:
--------------------------------------------
Thanks for the explanation [~fhueske]. From looking at the stack trace, this
doesn't actually look like an Optimizer problem because it slows down during
the initial Plan creation which happens before the optimization.
Perhaps we can optimize the Plan creation?
> Flink Planning is exponential in the number of stages
> -----------------------------------------------------
>
> Key: FLINK-10566
> URL: https://issues.apache.org/jira/browse/FLINK-10566
> Project: Flink
> Issue Type: Bug
> Components: Optimizer
> Affects Versions: 1.5.4, 1.6.1, 1.7.0
> Reporter: Robert Bradshaw
> Priority: Major
> Attachments: chart.png
>
>
> This makes it nearly impossible to run graphs with 100 or more stages. (The
> execution itself is still sub-second, but the job submission takes
> increasingly long.)
> I can reproduce this with the following pipeline, which resembles my
> real-world workloads (with depth up to 10 and width up, and past, 50). On
> Flink it seems getting width beyond width 10 is problematic (times out after
> hours). Note the log scale on the chart for time.
>
> {code:java}
> public static void runPipeline(int depth, int width) throws Exception {
> final ExecutionEnvironment env =
> ExecutionEnvironment.getExecutionEnvironment();
> DataSet<String> input = env.fromElements("a", "b", "c");
> DataSet<String> stats = null;
> for (int i = 0; i < depth; i++) {
> stats = analyze(input, stats, width / (i + 1) + 1);
> }
> stats.writeAsText("out.txt");
> env.execute("depth " + depth + " width " + width);
> }
> public static DataSet<String> analyze(DataSet<String> input,
> DataSet<String> stats, int branches) {
> System.out.println("analyze " + branches);
> for (int i = 0; i < branches; i++) {
> final int ii = i;
> if (stats != null) {
> input = input.map(new RichMapFunction<String, String>() {
> @Override
> public void open(Configuration parameters) throws Exception {
> Collection<String> broadcastSet =
> getRuntimeContext().getBroadcastVariable("stats");
> }
> @Override
> public String map(String value) throws Exception {
> return value;
> }
> }).withBroadcastSet(stats.map(s -> "(" + s + ").map"), "stats");
> }
> DataSet<String> branch = input
> .map(s -> new Tuple2<Integer, String>(0, s +
> ii))
> .groupBy(0)
> .minBy(1)
> .map(kv -> kv.f1);
> if (stats == null) {
> stats = branch;
> } else {
> stats = stats.union(branch);
> }
> }
> return stats.map(s -> "(" + s + ").stats");
> }
> {code}
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