Fair intersection of seekable iterators

TL;DR

This paper introduces a fairness-based approach to implementing worst-case optimal joins using seekable iterators, inspired by miniKanren's strategy for interleaving disjunct exploration, applicable in functional programming.

Contribution

It presents a novel, compositional method for worst-case optimal joins leveraging bounded work fairness, extending ideas from miniKanren's search strategy.

Findings

Fairness via bounded work enables efficient join implementations.

The approach is suitable for shallow embedding in functional languages.

Demonstrates a new intersection technique for seekable iterators.

Abstract

miniKanren's key semantic advance over Prolog is to implement a complete yet efficient search strategy, fairly interleaving execution between disjuncts. This fairness is accomplished by bounding how much work is done exploring one disjunct before switching to the next. We show that the same idea -- fairness via bounded work -- underlies an elegant compositional approach to implementing worst-case optimal joins using a seekable iterator interface, suitable for shallow embedding in functional languages.