andygrove opened a new pull request, #19589: URL: https://github.com/apache/datafusion/pull/19589
## 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. --> - Closes #. ## Rationale for this change I ran some microbenchmarks comparing DataFusion and DuckDB (see https://github.com/apache/datafusion-benchmarks/pull/28) and found that `CASE WHEN` expressions were much slower in DataFusion, so I asked Claude to make it go faster. ## 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. --> This adds a new optimization path for searched CASE WHEN expressions (CASE WHEN condition THEN result) with 3 or more branches. Instead of evaluating conditions sequentially on progressively shrinking batches, this approach: 1. Evaluates all conditions upfront on the full batch 2. Builds a branch_index array indicating which branch matched each row 3. Filters once per branch and evaluates THEN expressions This provides better performance due to: - Better cache locality (conditions evaluated on same data) - Simpler filter predicates (integer equality vs boolean expressions) - No progressive batch shrinking overhead **Important**: This changes short-circuit semantics for CONDITIONS (not THEN expressions). All conditions are evaluated even for rows where an earlier condition matched. This is safe for simple comparisons but may cause issues if conditions can error (e.g., division by zero in a condition). 🤖 Generated with [Claude Code](https://claude.com/claude-code) ## Are these changes tested? <!-- We typically require tests for all PRs in order to: 1. Prevent the code from being accidentally broken by subsequent changes 2. 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)? --> Existing tests ## Are there any user-facing changes? <!-- If there are user-facing changes then we may require documentation to be updated before approving the PR. --> No <!-- 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: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
