Fast Compilation and Execution of SQL Queries with WebAssembly

Abstract

Interpreted execution of queries, as in the vectorized model, suffers from interpretation overheads. By compiling queries this interpretation overhead is eliminated at the cost of a compilation phase that delays execution, sacrificing latency for throughput. For short-lived queries, minimizing latency is important, while for longrunning queries throughput outweighs latency. Because neither a purely interpretive model nor a purely compiling model can provide low latency and high throughput, adaptive solutions emerged. Adaptive systems seamlessly transition from interpreted to compiled execution, achieving low latency for short-lived queries and high throughput for long-running queries. However, these adaptive systems pose an immense development effort and require expert knowledge in both interpreter and compiler design.In this work, we investigate query execution by compilation to WebAssembly. We are able to compile even complex queries in less than a millisecond to machine code with near-optimal performance. By delegating execution of WebAssembly to the V8 engine, we are able to seamlessly transition from rapidly compiled yet nonoptimized code to thoroughly optimized code during execution. Our approach provides both low latency and high throughput, is adaptive out of the box, and is straight forward to implement. The drastically reduced compilation times even enable us to explore generative programming of library code, that is fully inlined by construction. Our experimental evaluation confirms that our approach yields competitive and sometimes superior performance.