presto-base-jdbc/src/main/java/io/prestosql/plugin/jdbc/StandardColumnMappings.java/StandardColumnMappings/charWriteFunction
class StandardColumnMappings:    public static SliceWriteFunction charWriteFunction()
    {
        return (statement, index, value) -> {
            statement.setString(index, value.toStringUtf8());
        };
    }