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Posted to github@datafusion.apache.org by "akupchinskiy (via GitHub)" <gi...@apache.org> on 2025/08/16 12:39:56 UTC
[PR] fix: potential native broadcast failure in scenarios with ReusedExhange [datafusion-comet]
akupchinskiy opened a new pull request, #2167:
URL: https://github.com/apache/datafusion-comet/pull/2167
## Which issue does this PR close?
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Closes #.
## Rationale for this change
Current CometBroadcast implementation might cause some complex plans to fail during the execution. If an execution stage involves several broadcasts and one of them corresponds to the evaluated before (ReusedExchange scenario), it might fail due to attempt to zip unaligned partitions [here](https://github.com/apache/datafusion-comet/blob/2b0e6db77b2c27bfa91eb34d0a2469d1014c20e6/spark/src/main/scala/org/apache/spark/sql/comet/operators.scala#L306) or [here](https://github.com/apache/datafusion-comet/blob/2b0e6db77b2c27bfa91eb34d0a2469d1014c20e6/spark/src/main/scala/org/apache/spark/sql/comet/operators.scala#L292).
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Initially, I have faced it when I was trying to run TPCDS benchmark on 10-factor scaled dataset with Spark-4: multiple queries failed with a similar error. Yet, it is reproducible for 3.5 version at least (the unit test included in the PR fails if run against main branch code).
## What changes are included in this PR?
Basically, the fix prevents picking ReusedExchange plan as a driving RDD (one which determines the target partitions number). Also, there is a workaround for another problem with ReusedExchangeExec: [this partition alignment](https://github.com/apache/datafusion-comet/blob/2b0e6db77b2c27bfa91eb34d0a2469d1014c20e6/spark/src/main/scala/org/apache/spark/sql/comet/operators.scala#L279) simply doesn't work for already evaluated broadcasted rdds. That is why it is necessary to align all the partitions CometBatchRDD inputs serving as broadcast wrappers. After that, all RDD have the same partitions number and zipping them works with no errors.
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## How are these changes tested?
Added a unit which fails against main branch; rebuilt the jar with proposed changes and rerun TPCDS-SF10 benchmark using spark-4.0 with no errors.
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Re: [PR] fix: potential native broadcast failure in scenarios with ReusedExhange [datafusion-comet]
Posted by "parthchandra (via GitHub)" <gi...@apache.org>.
parthchandra commented on PR #2167:
URL: https://github.com/apache/datafusion-comet/pull/2167#issuecomment-3246260793
@viirya would you be able to look at this?
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Re: [PR] fix: potential native broadcast failure in scenarios with ReusedExhange [datafusion-comet]
Posted by "akupchinskiy (via GitHub)" <gi...@apache.org>.
akupchinskiy commented on PR #2167:
URL: https://github.com/apache/datafusion-comet/pull/2167#issuecomment-3208985411
@comphead I think I found the breaking change making it fail in spark 4: https://issues.apache.org/jira/browse/SPARK-48195
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Re: [PR] fix: potential native broadcast failure in scenarios with ReusedExhange [datafusion-comet]
Posted by "viirya (via GitHub)" <gi...@apache.org>.
viirya commented on PR #2167:
URL: https://github.com/apache/datafusion-comet/pull/2167#issuecomment-3246353347
> @viirya would you be able to look at this?
I will take a look but maybe not very soon.
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Re: [PR] test: potential native broadcast failure in scenarios with ReusedExhange [datafusion-comet]
Posted by "andygrove (via GitHub)" <gi...@apache.org>.
andygrove merged PR #2167:
URL: https://github.com/apache/datafusion-comet/pull/2167
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Re: [PR] fix: potential native broadcast failure in scenarios with ReusedExhange [datafusion-comet]
Posted by "akupchinskiy (via GitHub)" <gi...@apache.org>.
akupchinskiy commented on PR #2167:
URL: https://github.com/apache/datafusion-comet/pull/2167#issuecomment-3208043464
> Thanks @akupchinskiy I checked it failed now on main
>
> ```
> org.apache.comet.CometRuntimeException: Partition number mismatch: 3 != 4
> ```
>
> Any reason the first partition number is taken? Can it be an issue if this value would be too small/large comparing to others?
I believe it just picks the first from plan traversal output which might even be undetermined at least in cases when AQE is on. In simple scenarios, there is only one non-broadcast plan in the list - so usually it is no issue. The more explicit way to reproduce it is to run TPCDS query set on comet build for spark 4.0: ~15 queries fail with the same error, and all of them run with no error on the patched version. I have not figured out the root cause of this regression though
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Re: [PR] fix: potential native broadcast failure in scenarios with ReusedExhange [datafusion-comet]
Posted by "codecov-commenter (via GitHub)" <gi...@apache.org>.
codecov-commenter commented on PR #2167:
URL: https://github.com/apache/datafusion-comet/pull/2167#issuecomment-3215418351
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:x: Patch coverage is `31.25000%` with `11 lines` in your changes missing coverage. Please review.
:white_check_mark: Project coverage is 34.64%. Comparing base ([`f09f8af`](https://app.codecov.io/gh/apache/datafusion-comet/commit/f09f8af64c6599255e116a376f4f008f2fd63b43?dropdown=coverage&el=desc&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=apache)) to head ([`9c62ea5`](https://app.codecov.io/gh/apache/datafusion-comet/commit/9c62ea5c5151244b13418e733f35318684c7e4c5?dropdown=coverage&el=desc&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=apache)).
:warning: Report is 408 commits behind head on main.
| [Files with missing lines](https://app.codecov.io/gh/apache/datafusion-comet/pull/2167?dropdown=coverage&src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=apache) | Patch % | Lines |
|---|---|---|
| [...n/scala/org/apache/spark/sql/comet/operators.scala](https://app.codecov.io/gh/apache/datafusion-comet/pull/2167?src=pr&el=tree&filepath=spark%2Fsrc%2Fmain%2Fscala%2Forg%2Fapache%2Fspark%2Fsql%2Fcomet%2Foperators.scala&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=apache#diff-c3Bhcmsvc3JjL21haW4vc2NhbGEvb3JnL2FwYWNoZS9zcGFyay9zcWwvY29tZXQvb3BlcmF0b3JzLnNjYWxh) | 33.33% | [6 Missing and 4 partials :warning: ](https://app.codecov.io/gh/apache/datafusion-comet/pull/2167?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=apache) |
| [...e/spark/sql/comet/CometBroadcastExchangeExec.scala](https://app.codecov.io/gh/apache/datafusion-comet/pull/2167?src=pr&el=tree&filepath=spark%2Fsrc%2Fmain%2Fscala%2Forg%2Fapache%2Fspark%2Fsql%2Fcomet%2FCometBroadcastExchangeExec.scala&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=apache#diff-c3Bhcmsvc3JjL21haW4vc2NhbGEvb3JnL2FwYWNoZS9zcGFyay9zcWwvY29tZXQvQ29tZXRCcm9hZGNhc3RFeGNoYW5nZUV4ZWMuc2NhbGE=) | 0.00% | [1 Missing :warning: ](https://app.codecov.io/gh/apache/datafusion-comet/pull/2167?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=apache) |
<details><summary>Additional details and impacted files</summary>
```diff
@@ Coverage Diff @@
## main #2167 +/- ##
=============================================
- Coverage 56.12% 34.64% -21.49%
+ Complexity 976 854 -122
=============================================
Files 119 143 +24
Lines 11743 13126 +1383
Branches 2251 2363 +112
=============================================
- Hits 6591 4547 -2044
- Misses 4012 7664 +3652
+ Partials 1140 915 -225
```
</details>
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Re: [PR] fix: potential native broadcast failure in scenarios with ReusedExhange [datafusion-comet]
Posted by "akupchinskiy (via GitHub)" <gi...@apache.org>.
akupchinskiy commented on PR #2167:
URL: https://github.com/apache/datafusion-comet/pull/2167#issuecomment-3324690682
The functionality of this MR got covered by recently merged https://github.com/apache/datafusion-comet/pull/2398 alongside with https://github.com/apache/datafusion-comet/pull/2420. So, the only thing worth keeping is a unit test :)
@comphead could you take a look?
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