Worked on the PRQL/prql repository to improve the reliability of SQL BETWEEN optimization within the compiler. Addressed a bug where the optimization logic depended on brittle span-based checks, which could lead to incorrect SQL generation for range filters. Refactored the implementation to use expression-kind-based comparison, ensuring more robust and accurate behavior. Added a regression test to lock in the fix and prevent future issues, demonstrating a focus on maintainability and correctness. Collaborated with other contributors throughout the process. The work leveraged skills in compiler development, Rust, and SQL, emphasizing careful debugging and targeted improvements to the codebase.