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BullFrog: Online Schema Evolution via Lazy Evaluation

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.

Quick Start

Using [BullFrog Docs] as a guide, we will walk you through the setup of BullFrog. To make it smoother, we record terminal sessions and share them on the web.


We extended Oltp-bench framework to measure online schema migration. You can find the experimental code in BullFrog-Oltpbench. If you have any questions about online schema migration on TPC-C Benchmark, feel free to contact me.