[
https://issues.apache.org/jira/browse/BEAM-7013?focusedWorklogId=293601&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-293601
]
ASF GitHub Bot logged work on BEAM-7013:
----------------------------------------
Author: ASF GitHub Bot
Created on: 13/Aug/19 04:48
Start Date: 13/Aug/19 04:48
Worklog Time Spent: 10m
Work Description: robinyqiu commented on pull request #9144: [BEAM-7013]
Integrating ZetaSketch's HLL++ algorithm with Beam
URL: https://github.com/apache/beam/pull/9144#discussion_r313218430
##########
File path:
sdks/java/extensions/zetasketch/src/main/java/org/apache/beam/sdk/extensions/zetasketch/HllCountMergePartialFn.java
##########
@@ -0,0 +1,151 @@
+/*
+ * 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.sdk.extensions.zetasketch;
+
+import com.google.zetasketch.HyperLogLogPlusPlus;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+import javax.annotation.Nullable;
+import org.apache.beam.sdk.coders.AtomicCoder;
+import org.apache.beam.sdk.coders.Coder;
+import org.apache.beam.sdk.coders.CoderRegistry;
+import org.apache.beam.sdk.coders.NullableCoder;
+import
org.apache.beam.sdk.extensions.zetasketch.HllCountMergePartialFn.HyperLogLogPlusPlusWrapper;
+import org.apache.beam.sdk.transforms.Combine;
+
+/**
+ * {@link Combine.CombineFn} for the {@link HllCount.MergePartial} combiner.
+ *
+ * @param <T> type of the HLL++ sketch to be merged
+ */
+class HllCountMergePartialFn<T>
+ extends Combine.CombineFn<byte[], HyperLogLogPlusPlusWrapper<T>, byte[]> {
+
+ // Call HllCountMergePartialFn.create() to instantiate
+ private HllCountMergePartialFn() {}
+
+ static HllCountMergePartialFn<?> create() {
+ 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> {
Review comment:
Thanks for your great suggestion the code is much simpler now!
Null is used to represent the "identity element" for merge operation, so
that the wrapper class can be removed now. And thanks to the existence of
`NullableCoder`, we can remove the other coder as well! To summarize, for
`Init` `HyperLogLogPlusPlusCoder<T>` is used; and for `MergePartial` a
`NullableCoder` wrapping a `HyperLogLogPlusPlusCoder<T>` is used.
> Using a null seems not 100% ideal, but I think using an Optional instead
would add a lot of overhead (another coder, ...)?
Totally agree. Using `Optional` is more meaningful here, but then we have to
write some extra code as its coder. So I used null instead, and annotated the
methods with `@Nullable` where it applies, and added some comments on that.
PTAL.
I will need to test this change thoroughly on Dataflow a bit later.
----------------------------------------------------------------
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.
For queries about this service, please contact Infrastructure at:
us...@infra.apache.org
Issue Time Tracking
-------------------
Worklog Id: (was: 293601)
Time Spent: 14h 50m (was: 14h 40m)
> 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: 14h 50m
> Remaining Estimate: 0h
>
--
This message was sent by Atlassian JIRA
(v7.6.14#76016)
