pgroll vs pt-online-schema-change

pgroll is an open-source command-line tool for PostgreSQL schema migrations that keeps old and new schema versions available while applications move between them. Its expand/contract workflow lets clients choose a version through PostgreSQL's search_path. The project describes migrations as zero-downtime and says it applies changes without locking the database; it can also backfill columns automatically when needed. For breaking changes, pgroll builds virtual schemas from views over physical tables and uses triggers to carry writes between old and new columns. Active migrations can be rolled back to the previous schema version. It supports PostgreSQL 14 and later, including RDS and Aurora, and is available for Linux, macOS, and Windows or self-hosting. It can convert SQL generated by ORMs, with examples for Alembic, Django, and Drizzle, though manual data migrations and SQL consolidation may be needed. On PostgreSQL 14, its versioned views do not respect row-level security policies, which can make it a poor choice for RLS users on that version. The project is licensed under Apache License 2.0.

pt-online-schema-change has no write-up on Specifiction yet; its figures are above.