Worked on the apache/calcite repository to address a query optimization issue involving window functions and LIMIT clauses. Focused on Java development and database optimization, the work involved updating the Calcite RelBuilder to ensure that window function calculations are preserved when LIMIT is pushed down, preventing incorrect query plans. The solution included implementing a regression test to validate the correct behavior of LIMIT with window functions, ensuring future reliability. This targeted bug fix demonstrated a careful approach to query planning and regression safety, with all changes documented and traceable. The work reflects depth in understanding complex SQL optimization scenarios and Java-based systems.