Worked on backend stability and reliability improvements for the crossoverJie/starrocks repository, focusing on the SQL analyzer component. Addressed two critical bugs over two months, first by refining logic to prevent nested analytic expressions from being misprocessed within window function analysis, and then by enhancing error handling for invalid LIKE and REGEXP patterns using Java and SQL. Introduced regression tests to ensure ongoing correctness and to guard against future regressions. The work improved traceability and robustness in query validation, reduced cryptic error messages, and increased the reliability of analytics-heavy workloads by strengthening both logic and test coverage in the codebase.