Casey Wilkinson developed support for DDL IF EXISTS and IF NOT EXISTS clauses in the zendesk/maxwell repository, focusing on MariaDB and MySQL schema changes. Using ANTLR grammar and Java, Casey extended SQL parsing and generation logic to handle these clauses in ALTER TABLE and INDEX statements, enabling safer database migrations. The work included refining grammar placement to prevent syntax errors and adding targeted unit tests to ensure correct behavior when database objects may not exist. By expanding test coverage and improving grammar accuracy, Casey enhanced deployment reliability and reduced the risk of regressions in schema-altering operations for the project.