This repository contains an experimental prototype of the system, which is not suitable for use in production.

BullFrog is a system that performs immediate schema migration in a single step, without advanced warning or time to prepare, including backwards-incompatible migrations. It implements concurrency control algorithms and data structures to enable concurrent processing of schema migration operations with post-migration transactions, while ensuring exactly-once migration of all old data into the physical layout required by the new schema.

BullFrog is an open source extension to PostgreSQL. Experiments using this prototype over a TPC-C based workload (supplemented to include schema migrations) show that BullFrog can achieve zero-downtime migration to non-trivial new schemas with near-invisible impact on transaction throughput and latency.

• Table Split Migration
• Aggregate Migration
• Join Migration

We experimentally evaluate the lazy migration algorithms of bullfrog and compare their performance under various configurations against two baselines.

• Eager Migration
• Multi-step Migration