Implementation of delayed updates in Heraclitus

Abstract

The Heraclitus languages are database programming languages that give prominence to “delayed updates” or deltas, which are first-class values representing sets of proposed updates, such as inserts and deletes, to the underlying persistent store. Deltas can be created, inspected and combined without committing to the given updates. Deltas are useful for realizing advanced database features that manipulate virtual database states in addition to the currently stored state; examples include supporting rule-based triggers, hypothetical reasoning, and concurrent transaction processing systems.

This paper introduces Heraclitus[Alg], a relational algebra extended by deltas, and the HERALD system that implements it. Heraclitus[Alg] is a low-level, internal language which will be used in the implementation of richer, calculus-style Heraclitus languages that have been previously proposed. HERALD is built on top of the Wisconsin Storage System (WiSS), and extends this system to support deltas and the various delta operators.

The first author was supported in part by the NSF under grant IRI-9110522 and the USC Faculty Research and Innovation Fund under grant 22-1509-9440. The second author was supported in part NSF grant IR1-9107055 and by the Defense Advanced Research Projects Agency under DARPA grant MDA903-81-C-0335. The third author supported in part by the German Academic Exchange Service. The research of the second and third authors supported in part by AT&T, and was performed in part while they were visiting the Technische Universität Berlin.