The Dev World – Sergio Lema

After using Alembic for several months, I feel like I can finally compare it with other database migration tools I’ve used before. And no, running raw SQL files manually is not a migration tool.

Before Alembic, I had experience with Flyway and Liquibase in my Java projects. Both tools have their quirks, but Alembic comes with a particularly interesting feature that other tools don’t have: a powerful way to handle migrations in teams. And let’s be honest, database migrations are already hard enough, having a tool that helps (instead of creating more headaches) is a big deal.

The Biggest Con: The Checksum Problem

Let’s start with the elephant in the room. The biggest issue I have with Alembic is its lack of checksum validation. Every other tool I’ve used keeps track of checksums for each migration file applied to the database. Alembic? Nope.

Why does this matter? Imagine I run a regex over all the project and updates accidentally a changeset. If I modify the migration file and then run it against a new database (like a fresh environment or after resetting my machine), the resulting database might not match the original.

The whole point of a migration tool is to ensure that every environment ends up with the same schema. If it can’t do that, then what are we even doing here?

The Biggest Pro: Handling Parallel

Now, let’s talk about what Alembic does right. One of its best features is how it handles multiple developers making database changes at the same time with branching.

With most migration tools, if two developers create changes simultaneously, the first one to merge their commit wins. The second developer is left dealing with the mess. In Alembic, when two changesets are created in parallel, I actually need to merge them explicitly.

At first, this sounds annoying, like dealing with a Git conflict. But in reality, it’s a lifesaver. Instead of blindly applying migrations in whatever order Git happens to pick, I can control how they are merged and resolve any conflicts in a structured way. This prevents a ton of potential problems down the road.

Another great advantage? Every changeset includes a rollback action. No way to forget it. Unlike some other tools that treat rollbacks like an afterthought (or worse, leave them up to developers’ “good intentions”), Alembic makes sure I always define how to undo my changes.

Conclusion

One of the coolest things about Alembic is that I can write migrations using SQLAlchemy, which means I get to write migrations using an ORM. That’s great if you’re not super comfortable with raw SQL.

But for purists like me? I kind of miss writing straight SQL queries. There’s something satisfying about crafting a perfect SQL statement, watching it run, and knowing exactly what’s happening under the hood.

So, is Alembic perfect? No. But it does some things better than other tools, and for team-based development, it’s a solid choice. Just watch out for that checksum issue, and you’ll be fine.