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Posted to github@datafusion.apache.org by "andygrove (via GitHub)" <gi...@apache.org> on 2024/12/16 22:25:03 UTC

[PR] feat: Add additional metrics for shuffle write [datafusion-comet]

andygrove opened a new pull request, #1173:
URL: https://github.com/apache/datafusion-comet/pull/1173

   ## Which issue does this PR close?
   
   <!--
   We generally require a GitHub issue to be filed for all bug fixes and enhancements and this helps us generate change logs for our releases. You can link an issue to this PR using the GitHub syntax. For example `Closes #123` indicates that this PR will close issue #123.
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   N/A
   
   ## Rationale for this change
   
   <!--
    Why are you proposing this change? If this is already explained clearly in the issue then this section is not needed.
    Explaining clearly why changes are proposed helps reviewers understand your changes and offer better suggestions for fixes.  
   -->
   
   I would like to understand how much time is spent on shuffle writing.
   
   ## What changes are included in this PR?
   
   <!--
   There is no need to duplicate the description in the issue here but it is sometimes worth providing a summary of the individual changes in this PR.
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   - Introduce a new `write_time` native metric to record write time instead of using `elapsed_time`
   - Use `elapsed_time` to measure total native time (excluding executing the child plan and fetching data)
   - Add new `input_time` native metric for measuring the time for `ShuffleWriterExec` to execute the child plan and fetch its input data
   - Add new `shuffleWallTime` JVM metric to measure total time of shuffle
   - Update docs
   
   ## Spark UI
   
   ![Screenshot from 2024-12-16 15-21-24](https://github.com/user-attachments/assets/754530a2-688c-49a0-ab18-1ef515f9783a)
   
   ## Native plan
   
   ```
   ShuffleWriterExec: ..., metrics=[elapsed_compute=42.425493ms, ..., input_time=255.873165ms, write_time=462.517µs]
     ScanExec: source=[ShuffleWriterInput], metrics=[elapsed_compute=254.994282ms, ...]
   ```
   
   ## How are these changes tested?
   
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Re: [PR] feat: Add additional metrics for shuffle write [datafusion-comet]

Posted by "kazuyukitanimura (via GitHub)" <gi...@apache.org>.

kazuyukitanimura commented on code in PR #1173:
URL: https://github.com/apache/datafusion-comet/pull/1173#discussion_r1887700898


##########
docs/source/user-guide/metrics.md:
##########
@@ -0,0 +1,63 @@
+<!---
+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.
+-->
+
+# Comet Metrics
+
+## Spark SQL Metrics
+
+Set `spark.comet.metrics.detailed=true` to see all available Comet metrics.
+
+### CometScanExec
+
+`CometScanExec` uses nanoseconds for total scan time. Spark also measures scan time in nanoseconds but converts to

Review Comment:
   This sounds like a problem statement. Did you mean that `spark.comet.metrics.detailed=true` will not loose the precision?



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