Snakes on a Plan: Compiling Python Functions into Plain SQL Queries

Abstract

"Move your computation close to the data"is decades-old advice that is hard to follow if your code exhibits complex control flow. The runtime of such applications suffers from a continual back and forth between database-external code execution and plan-based SQL evaluation. We demonstrate the ByePy compiler which translates entire Python functions with arbitrary control flow-including deeply nested iteration-into plain recursive SQL:1999 queries. The invocation of a ByePy-compiled function enters the database engine once to execute the plan of a single query. Computation does not get much closer to the data than this. The system rewards this translation effort from Python to SQL with runtime improvements of up to an order of magnitude.