On Practical Considerations for the Adoption of Worst-Case Optimal Joins in RDBMSs
Worst-case optimal join (WCOJ) algorithms have attracted significant interest in both academia and industry due to their strong asymptotic performance guarantees. However, their integration into mature relational database management systems (RDBMSs) remains severely limited. Unlike prior theoretical surveys, this study analyzes the practical considerations for WCOJ adoption across three core query engine layers: interpretation, optimization, and execution, before extending to distributed environments. The findings indicate that the primary bottlenecks delaying widespread adoption are architectural rather than algorithmic. Specifically, WCOJ integration necessitates a fundamental shift in the optimization layer toward hybrid planning and new objective functions based on intersection costs. Furthermore, at the execution layer, the unpredictable pointer-chasing inherent to hierarchical index traversals creates severe hardware inefficiencies. By synthesizing ongoing research efforts, this survey provides a structured roadmap of engineering trade-offs to guide practitioners in successfully integrating WCOJs into conventional database architectures.