Christopher focused on improving query stability and correctness in the tarantool/datafusion repository, addressing a nuanced bug in the SortPreservingMergeExec component. He resolved an issue where SQL ORDER BY CASE expressions with NULL-bound intervals could trigger false error flags due to interval arithmetic ambiguities. By ensuring the engine returns UNCERTAIN for such cases, Christopher enhanced the reliability of complex SQL queries without altering user-facing behavior. He reinforced these changes with targeted unit tests, expanding regression coverage for edge scenarios. His work demonstrated careful application of Rust and SQL expertise, emphasizing maintainability and correctness in the interval handling logic for production environments.