The researchers developed a new optimizer for SAP HANA called the multi-way join aware optimizer to improve query performance for complex applications. Traditional optimizers only consider joining data in pairs, which can be inefficient. The new optimizer can handle joining data in groups of any size, making queries more efficient. By introducing the concept of join units, they reduce the unnecessary work of considering all possible joins. Through testing with real-world and simulated data, they showed that their new optimizer is better at handling complex queries compared to the older methods.