A SQL to C compiler in 500 lines of code. (2019)

• Record Type: Journal Article
• Authors: ROMPF, TIARK; AMIN, NADA
• Is Part Of: Journal of functional programming. Volume 29(2019)
• Publication Date: 2019
• Subjects: Functional programming (Computer science) -- Periodicals
• DOI: 10.1017/S0956796819000054
• Languages: English
• ISSNs: 0956-7968

Abstract

Abstract: 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 high-level 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 toward generative programming. The core of the query engine is an interpreter for relational-algebra operations, written in Scala. Using the open-source lightweight modular staging framework, 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: the first Futamura projection, which states that a process that can specialize an interpreter to any given input program is equivalent to a compiler. In this context, we discuss lightweight modular staging programming patterns such as mixed-stage data structures (e.g., data records with static schema and dynamic field components) and techniques to generate low-level C code, including specialized data structures and data loading primitives.