ctsk opened a new pull request, #14234: URL: https://github.com/apache/datafusion/pull/14234
## 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. --> This PR is an experiment to perform the hashing part of CollectLeft joins in parallel. Instead of directly coalescing the partitions on the build side of the hash join, I tried to perform the hashing for each partition separately, and coalesce the RecordBatches+Hashes afterwards. While this approach does perform the hashing of the build side in parallel, it also requires those hashes to be stored and accumulated in the HashJoinStream. **Benchmarking on TPCH showed no significant performance advantage.** ## What changes are included in this PR? 1. Introduce a Stream that attaches hashes to a given stream of RecordBatches + A variation of CoalescePartitions for this RecordBatch+Hash Stream data type. 2. Relax the distribution constraint for the build side of CollectLeft to UnspecifiedDistribution <!-- 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. --> ## Are these changes tested? Covered by the existing hash join test suite <!-- We typically require tests for all PRs in order to: 1. Prevent the code from being accidentally broken by subsequent changes 3. Serve as another way to document the expected behavior of the code If tests are not included in your PR, please explain why (for example, are they covered by existing tests)? --> ## Are there any user-facing changes? No. <!-- If there are user-facing changes then we may require documentation to be updated before approving the PR. --> <!-- If there are any breaking changes to public APIs, please add the `api change` label. --> -- 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. To unsubscribe, e-mail: github-unsubscr...@datafusion.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org --------------------------------------------------------------------- To unsubscribe, e-mail: github-unsubscr...@datafusion.apache.org For additional commands, e-mail: github-h...@datafusion.apache.org
