[GitHub] [beam] mosche commented on a diff in pull request #22446: Improved pipeline translation in SparkStructuredStreamingRunner

[GitBox <gi...@apache.org>]

mosche commented on code in PR #22446:
URL: https://github.com/apache/beam/pull/22446#discussion_r974006143


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runners/spark/3/src/main/java/org/apache/beam/runners/spark/structuredstreaming/translation/batch/Aggregators.java:
##########
@@ -0,0 +1,590 @@
+/*
+ * 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.beam.runners.spark.structuredstreaming.translation.batch;
+
+import static org.apache.beam.runners.spark.structuredstreaming.translation.helpers.EncoderHelpers.collectionEncoder;
+import static org.apache.beam.runners.spark.structuredstreaming.translation.helpers.EncoderHelpers.encoderOf;
+import static org.apache.beam.runners.spark.structuredstreaming.translation.helpers.EncoderHelpers.mapEncoder;
+import static org.apache.beam.runners.spark.structuredstreaming.translation.helpers.EncoderHelpers.mutablePairEncoder;
+import static org.apache.beam.sdk.transforms.windowing.PaneInfo.NO_FIRING;
+import static org.apache.beam.vendor.guava.v26_0_jre.com.google.common.base.Preconditions.checkArgument;
+import static org.apache.beam.vendor.guava.v26_0_jre.com.google.common.collect.Iterators.peekingIterator;
+
+import java.util.Collection;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.Map;
+import java.util.Map.Entry;
+import java.util.Set;
+import java.util.TreeMap;
+import java.util.function.BiFunction;
+import java.util.function.BinaryOperator;
+import java.util.function.Function;
+import javax.annotation.Nullable;
+import org.apache.beam.runners.spark.structuredstreaming.translation.utils.ScalaInterop.Fun1;
+import org.apache.beam.sdk.transforms.Combine.CombineFn;
+import org.apache.beam.sdk.transforms.windowing.BoundedWindow;
+import org.apache.beam.sdk.transforms.windowing.IntervalWindow;
+import org.apache.beam.sdk.transforms.windowing.Sessions;
+import org.apache.beam.sdk.transforms.windowing.TimestampCombiner;
+import org.apache.beam.sdk.transforms.windowing.WindowFn;
+import org.apache.beam.sdk.util.WindowedValue;
+import org.apache.beam.sdk.values.WindowingStrategy;
+import org.apache.beam.vendor.guava.v26_0_jre.com.google.common.collect.Collections2;
+import org.apache.beam.vendor.guava.v26_0_jre.com.google.common.collect.ImmutableList;
+import org.apache.beam.vendor.guava.v26_0_jre.com.google.common.collect.ImmutableSet;
+import org.apache.beam.vendor.guava.v26_0_jre.com.google.common.collect.PeekingIterator;
+import org.apache.beam.vendor.guava.v26_0_jre.com.google.common.collect.Sets;
+import org.apache.spark.sql.Encoder;
+import org.apache.spark.sql.expressions.Aggregator;
+import org.apache.spark.util.MutablePair;
+import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
+import org.checkerframework.checker.nullness.qual.NonNull;
+import org.checkerframework.checker.nullness.qual.PolyNull;
+import org.joda.time.Instant;
+
+public class Aggregators {
+
+  /**
+   * Creates simple value {@link Aggregator} that is not window aware.
+   *
+   * @param <ValT> {@link CombineFn} input type
+   * @param <AccT> {@link CombineFn} accumulator type
+   * @param <ResT> {@link CombineFn} / {@link Aggregator} result type
+   * @param <InT> {@link Aggregator} input type
+   */
+  public static <ValT, AccT, ResT, InT> Aggregator<InT, ?, ResT> value(
+      CombineFn<ValT, AccT, ResT> fn,
+      Fun1<InT, ValT> valueFn,
+      Encoder<AccT> accEnc,
+      Encoder<ResT> outEnc) {
+    return new ValueAggregator<>(fn, valueFn, accEnc, outEnc);
+  }
+
+  /**
+   * Creates windowed Spark {@link Aggregator} depending on the provided Beam {@link WindowFn}s.
+   *
+   * <p>Specialised implementations are provided for:
+   * <li>{@link Sessions}
+   * <li>Non merging window functions
+   * <li>Merging window functions
+   *
+   * @param <ValT> {@link CombineFn} input type
+   * @param <AccT> {@link CombineFn} accumulator type
+   * @param <ResT> {@link CombineFn} / {@link Aggregator} result type
+   * @param <InT> {@link Aggregator} input type
+   */
+  public static <ValT, AccT, ResT, InT>
+      Aggregator<WindowedValue<InT>, ?, Collection<WindowedValue<ResT>>> windowedValue(
+          CombineFn<ValT, AccT, ResT> fn,
+          Fun1<WindowedValue<InT>, ValT> valueFn,
+          WindowingStrategy<?, ?> windowing,
+          Encoder<BoundedWindow> windowEnc,
+          Encoder<AccT> accEnc,
+          Encoder<WindowedValue<ResT>> outEnc) {
+    if (!windowing.needsMerge()) {
+      return new NonMergingWindowedAggregator<>(fn, valueFn, windowing, windowEnc, accEnc, outEnc);
+    } else if (windowing.getWindowFn().getClass().equals(Sessions.class)) {
+      return new SessionsAggregator<>(fn, valueFn, windowing, (Encoder) windowEnc, accEnc, outEnc);
+    }
+    return new MergingWindowedAggregator<>(fn, valueFn, windowing, windowEnc, accEnc, outEnc);
+  }
+
+  /**
+   * Simple value {@link Aggregator} that is not window aware.
+   *
+   * @param <ValT> {@link CombineFn} input type
+   * @param <AccT> {@link CombineFn} accumulator type
+   * @param <ResT> {@link CombineFn} / {@link Aggregator} result type
+   * @param <InT> {@link Aggregator} input type
+   */
+  private static class ValueAggregator<ValT, AccT, ResT, InT>
+      extends CombineFnAggregator<ValT, AccT, ResT, InT, AccT, ResT> {
+
+    public ValueAggregator(
+        CombineFn<ValT, AccT, ResT> fn,
+        Fun1<InT, ValT> valueFn,
+        Encoder<AccT> accEnc,
+        Encoder<ResT> outEnc) {
+      super(fn, valueFn, accEnc, outEnc);
+    }
+
+    @Override
+    public AccT zero() {
+      return emptyAcc();
+    }
+
+    @Override
+    public AccT reduce(AccT buff, InT in) {
+      return addToAcc(buff, value(in));
+    }
+
+    @Override
+    public AccT merge(AccT b1, AccT b2) {
+      return mergeAccs(b1, b2);
+    }
+
+    @Override
+    public ResT finish(AccT buff) {
+      return extract(buff);
+    }
+  }
+
+  /**
+   * Specialized windowed Spark {@link Aggregator} for Beam {@link WindowFn}s of type {@link
+   * Sessions}. The aggregator uses a {@link TreeMap} as buffer to maintain ordering of the {@link
+   * IntervalWindow}s and merge these more efficiently.
+   *
+   * <p>For efficiency, this aggregator re-implements {@link
+   * Sessions#mergeWindows(WindowFn.MergeContext)} to leverage the already sorted buffer.
+   *
+   * @param <ValT> {@link CombineFn} input type
+   * @param <AccT> {@link CombineFn} accumulator type
+   * @param <ResT> {@link CombineFn} / {@link Aggregator} result type
+   * @param <InT> {@link Aggregator} input type
+   */
+  private static class SessionsAggregator<ValT, AccT, ResT, InT>
+      extends WindowedAggregator<
+          ValT,
+          AccT,
+          ResT,
+          InT,
+          IntervalWindow,
+          TreeMap<IntervalWindow, MutablePair<Instant, AccT>>> {
+
+    SessionsAggregator(
+        CombineFn<ValT, AccT, ResT> combineFn,
+        Fun1<WindowedValue<InT>, ValT> valueFn,
+        WindowingStrategy<?, ?> windowing,
+        Encoder<IntervalWindow> windowEnc,
+        Encoder<AccT> accEnc,
+        Encoder<WindowedValue<ResT>> outEnc) {
+      super(combineFn, valueFn, windowing, windowEnc, accEnc, outEnc, (Class) TreeMap.class);
+      checkArgument(windowing.getWindowFn().getClass().equals(Sessions.class));
+    }
+
+    @Override
+    public final TreeMap<IntervalWindow, MutablePair<Instant, AccT>> zero() {
+      return new TreeMap<>();
+    }
+
+    @Override
+    @SuppressWarnings("keyfor")
+    public TreeMap<IntervalWindow, MutablePair<Instant, AccT>> reduce(
+        TreeMap<IntervalWindow, MutablePair<Instant, AccT>> buff, WindowedValue<InT> input) {
+      for (IntervalWindow window : (Collection<IntervalWindow>) input.getWindows()) {
+        @MonotonicNonNull MutablePair<Instant, AccT> acc = null;
+        @MonotonicNonNull IntervalWindow first = null, last = null;
+        // start with window before or equal to new window (if exists)
+        @Nullable Entry<IntervalWindow, MutablePair<Instant, AccT>> lower = buff.floorEntry(window);
+        if (lower != null && window.intersects(lower.getKey())) {
+          // if intersecting, init accumulator and extend window to span both
+          acc = lower.getValue();
+          window = window.span(lower.getKey());
+          first = last = lower.getKey();
+        }
+        // merge following windows in order while intersecting
+        for (Entry<IntervalWindow, MutablePair<Instant, AccT>> entry :
+            buff.tailMap(window, false).entrySet()) {
+          MutablePair<Instant, AccT> entryAcc = entry.getValue();
+          IntervalWindow entryWindow = entry.getKey();
+          if (window.intersects(entryWindow)) {
+            // extend window and merge accumulators
+            window = window.span(entryWindow);
+            acc = acc == null ? entryAcc : mergeAccs(window, acc, entryAcc);
+            if (first == null) {
+              first = last = entryWindow;
+            } else {
+              last = entryWindow;
+            }
+          } else {
+            break; // stop, later windows won't intersect either
+          }
+        }
+        if (first != null && last != null) {
+          // remove entire merged subset from first to last
+          buff.navigableKeySet().subSet(first, true, last, true).clear();
+        }
+        // add input and get accumulator for new (potentially merged) window
+        buff.put(window, addToAcc(window, acc, value(input), input.getTimestamp()));
+      }
+      return buff;
+    }
+
+    @Override
+    public TreeMap<IntervalWindow, MutablePair<Instant, AccT>> merge(
+        TreeMap<IntervalWindow, MutablePair<Instant, AccT>> b1,
+        TreeMap<IntervalWindow, MutablePair<Instant, AccT>> b2) {
+      if (b1.isEmpty()) {
+        return b2;
+      } else if (b2.isEmpty()) {
+        return b1;
+      }
+      // Init new tree map to merge both buffers
+      TreeMap<IntervalWindow, MutablePair<Instant, AccT>> res = zero();
+      PeekingIterator<Entry<IntervalWindow, MutablePair<Instant, AccT>>> it1 =
+          peekingIterator(b1.entrySet().iterator());
+      PeekingIterator<Entry<IntervalWindow, MutablePair<Instant, AccT>>> it2 =
+          peekingIterator(b2.entrySet().iterator());
+
+      @Nullable MutablePair<Instant, AccT> acc = null;

Review Comment:
   You're right logically, but checker cannot prove that and will fail ...



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