[ 
https://issues.apache.org/jira/browse/BEAM-7013?focusedWorklogId=295527&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-295527
 ]

ASF GitHub Bot logged work on BEAM-7013:
----------------------------------------

                Author: ASF GitHub Bot
            Created on: 15/Aug/19 16:33
            Start Date: 15/Aug/19 16:33
    Worklog Time Spent: 10m 
      Work Description: zfraa commented on pull request #9144: [BEAM-7013] 
Integrating ZetaSketch's HLL++ algorithm with Beam
URL: https://github.com/apache/beam/pull/9144#discussion_r313891470
 
 

 ##########
 File path: 
sdks/java/extensions/zetasketch/src/main/java/org/apache/beam/sdk/extensions/zetasketch/HllCountMergePartialFn.java
 ##########
 @@ -44,109 +37,55 @@ private HllCountMergePartialFn() {}
     return new HllCountMergePartialFn();
   }
 
-  /**
-   * Accumulator for the {@link HllCount.MergePartial} combiner. Cannot use 
{@link
-   * HyperLogLogPlusPlus} directly because we need an "identity element" for 
the {@code merge}
-   * operation, and we are not able to create such "identity element" of type 
{@link
-   * HyperLogLogPlusPlus} without knowing the sketch precision and value type.
-   */
-  static final class HyperLogLogPlusPlusWrapper<T> {
-    @Nullable private HyperLogLogPlusPlus<T> hll;
-
-    private HyperLogLogPlusPlusWrapper(@Nullable HyperLogLogPlusPlus<T> hll) {
-      this.hll = hll;
-    }
-  }
-
-  /**
-   * Coder for the {@link HyperLogLogPlusPlusWrapper} class with generic type 
parameter {@code T}.
-   */
-  private static final class HyperLogLogPlusPlusWrapperCoder<T>
-      extends AtomicCoder<HyperLogLogPlusPlusWrapper<T>> {
-
-    private static final HyperLogLogPlusPlusWrapperCoder<?> INSTANCE =
-        new HyperLogLogPlusPlusWrapperCoder<>();
-
-    private final Coder<HyperLogLogPlusPlus<T>> nullableHllCoder =
-        NullableCoder.of(HyperLogLogPlusPlusCoder.of());
-
-    // Generic singleton factory pattern; the coder works for all 
HyperLogLogPlusPlusWrapper objects
-    // at runtime regardless of type T
-    @SuppressWarnings("unchecked")
-    static <T> HyperLogLogPlusPlusWrapperCoder<T> of() {
-      return (HyperLogLogPlusPlusWrapperCoder<T>) INSTANCE;
-    }
-
-    @Override
-    public void encode(HyperLogLogPlusPlusWrapper<T> value, OutputStream 
outStream)
-        throws IOException {
-      nullableHllCoder.encode(value.hll, outStream);
-    }
-
-    @Override
-    public HyperLogLogPlusPlusWrapper<T> decode(InputStream inStream) throws 
IOException {
-      return new 
HyperLogLogPlusPlusWrapper<T>(nullableHllCoder.decode(inStream));
-    }
-
-    @Override
-    public void verifyDeterministic() throws NonDeterministicException {
-      nullableHllCoder.verifyDeterministic();
-    }
-  }
-
   @Override
-  public Coder<HyperLogLogPlusPlusWrapper<T>> getAccumulatorCoder(
+  public Coder<HyperLogLogPlusPlus<T>> getAccumulatorCoder(
       CoderRegistry registry, Coder<byte[]> inputCoder) {
-    return HyperLogLogPlusPlusWrapperCoder.of();
+    return NullableCoder.of(HyperLogLogPlusPlusCoder.of());
   }
 
   @Override
-  public HyperLogLogPlusPlusWrapper<T> createAccumulator() {
-    return new HyperLogLogPlusPlusWrapper<>(null);
+  public HyperLogLogPlusPlus<T> createAccumulator() {
+    return null;
   }
 
   @Override
-  public HyperLogLogPlusPlusWrapper<T> addInput(
-      HyperLogLogPlusPlusWrapper<T> accumulator, byte[] input) {
-    if (accumulator.hll == null) {
+  public HyperLogLogPlusPlus<T> addInput(HyperLogLogPlusPlus<T> accumulator, 
byte[] input) {
+    if (accumulator == null) {
       @SuppressWarnings("unchecked")
-      HyperLogLogPlusPlus<T> hll = (HyperLogLogPlusPlus<T>) 
HyperLogLogPlusPlus.forProto(input);
-      accumulator.hll = hll;
+      HyperLogLogPlusPlus<T> result = (HyperLogLogPlusPlus<T>) 
HyperLogLogPlusPlus.forProto(input);
+      return result;
     } else {
-      accumulator.hll.merge(input);
+      accumulator.merge(input);
+      return accumulator;
     }
-    return accumulator;
   }
 
   @Override
-  public HyperLogLogPlusPlusWrapper<T> mergeAccumulators(
-      Iterable<HyperLogLogPlusPlusWrapper<T>> accumulators) {
-    HyperLogLogPlusPlusWrapper<T> merged = createAccumulator();
-    for (HyperLogLogPlusPlusWrapper<T> accumulator : accumulators) {
-      if (accumulator.hll == null) {
+  public HyperLogLogPlusPlus<T> 
mergeAccumulators(Iterable<HyperLogLogPlusPlus<T>> accumulators) {
+    HyperLogLogPlusPlus<T> merged = createAccumulator();
 
 Review comment:
   Why not set this to null directly? (I find that easier to read, but up to 
your preference!)
 
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Issue Time Tracking
-------------------

    Worklog Id:     (was: 295527)
    Time Spent: 17h 40m  (was: 17.5h)

> A new count distinct transform based on BigQuery compatible HyperLogLog++ 
> implementation
> ----------------------------------------------------------------------------------------
>
>                 Key: BEAM-7013
>                 URL: https://issues.apache.org/jira/browse/BEAM-7013
>             Project: Beam
>          Issue Type: New Feature
>          Components: extensions-java-sketching, sdk-java-core
>            Reporter: Yueyang Qiu
>            Assignee: Yueyang Qiu
>            Priority: Major
>             Fix For: 2.16.0
>
>          Time Spent: 17h 40m
>  Remaining Estimate: 0h
>




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