Functional pearl: a SQL to C compiler in 500 lines of code

Tiark Rompf, Nada Amin
2015 Proceedings of the 20th ACM SIGPLAN International Conference on Functional Programming - ICFP 2015  
We present the design and implementation of a SQL query processor that outperforms existing database systems and is written in just about 500 lines of Scala code -a convincing case study that highlevel functional programming can handily beat C for systems-level programming where the last drop of performance matters. The key enabler is a shift in perspective towards generative programming. The core of the query engine is an interpreter for relational algebra operations, written in Scala. Using
more » ... e opensource LMS Framework (Lightweight Modular Staging), we turn this interpreter into a query compiler with very low effort. To do so, we capitalize on an old and widely known result from partial evaluation known as Futamura projections, which state that a program that can specialize an interpreter to any given input program is equivalent to a compiler. In this pearl, we discuss LMS programming patterns such as mixed-stage data structures (e.g. data records with static schema and dynamic field components) and techniques to generate lowlevel C code, including specialized data structures and data loading primitives.
doi:10.1145/2784731.2784760 dblp:conf/icfp/RompfA15 fatcat:tbfka7wnurfm5b7mrmjbwqudj4