ethan-tyler opened a new pull request, #9220: URL: https://github.com/apache/arrow-rs/pull/9220
Fix arrow-cast failing to cast into Dictionary(K, Utf8View) and Dictionary(K, BinaryView) even though can_cast_types returns true. # Which issue does this PR close? - Closes #9219. <!-- 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. --> # Rationale for this change Downstream pipelines may require view-typed schemas (e.g. schema_force_view_types) while still dictionary-encoding columns for memory efficiency. Even with view types, dictionary encoding can reduce per-row memory (1–4 byte keys vs 16-byte views) for low-cardinality columns. Today there's no way to materialize Dictionary(K, Utf8View/BinaryView) via arrow-cast. <!-- 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? Add Utf8View and BinaryView support in cast_to_dictionary using a two-step pack to recast approach: - Pack to Dictionary(K, Utf8/Binary) - Cast dictionary values to Utf8View/BinaryView via existing cast machinery <!-- 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? - StringArray/StringViewArray to Dictionary(UInt16, Utf8View) (including sliced inputs) - BinaryArray/BinaryViewArray to Dictionary(UInt16, BinaryView) (including sliced inputs) - Key overflow for Dictionary(UInt8, Utf8View) - Empty and all-null inputs <!-- 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? 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 call them out. --> -- 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]
