Cherry-pick 7d294f1dc (dict type coercion fix) #55
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apache#18099) ## 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 apache#123` indicates that this PR will close issue apache#123. --> Fixes comparison errors when using dictionary-encoded types with comparison functions like NULLIF. ## Rationale for this change When using dictionary-encoded columns (e.g., Dictionary(Int32, Utf8)) in comparison operations with literals or other types, DataFusion would throw an error stating the types are not comparable. This was particularly problematic for functions like NULLIF which rely on comparison coercion. The issue was that comparison_coercion_numeric didn't handle dictionary types, even though the general comparison_coercion function did have dictionary support. <!-- 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. --> ## What changes are included in this PR? 1. Refactored dictionary comparison logic: Extracted common dictionary coercion logic into dictionary_comparison_coercion_generic to avoid code duplication. 2. Added numeric-specific dictionary coercion: Introduced dictionary_comparison_coercion_numeric that uses numeric-preferring comparison rules when dealing with dictionary value types. 3. Updated comparison_coercion_numeric: Added a call to dictionary_comparison_coercion_numeric in the coercion chain to properly handle dictionary types. 4. Added sqllogictest cases demonstrating the fix works for various dictionary comparison scenarios. <!-- 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? Yes, added tests in datafusion/sqllogictest/test_files/nullif.slt covering: - Dictionary type compared with string literal - String compared with dictionary type - Dictionary compared with dictionary All tests pass with the fix and would fail without it. <!-- 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)? --> ## Are there any user-facing changes? This is a bug fix that enables previously failing queries to work correctly. No breaking changes or API modifications. <!-- 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. -->
LiaCastaneda
approved these changes
Oct 20, 2025
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Cherry-pick apache#18099