How to run 'up' migrations on only updated server?

[perqin]

I know that the README mentions it, but I just can't understand it well.

Let's say that my server app V1 requires a database in some schema A. And later V2 changes to schema to B, later V3 changes to schema C.

So, I will define 2 migrations: A_to_B and B_to_C. Now that I want the V3 version will:

1. Run A_to_B and B_to_C on schema A (that is, upgrade from V1 to V3).
2. Run B_to_C on schema B (that is, upgrade from V2 to V3).
3. Run nothing on schema C or empty database.

If the requirement 3 is excluded, I can just run all pending migrations, but I want it not to run any migrations on empty database. How to achieve that?

[ephemer]

I think you'd just have to add the info that these migrations are already complete into your new (fresh) database, or write your migrations such that they ignore an empty db.