Alembic dependency resolution with depends_on

Question

I'm working on a project with multiple branches, and I'm finding something funny when running my migrations...

I have a main branch that has the following revisions: A --> B --> C

And then a dev branch with B' --> C'

B' depends on B, and C' depends on C

C has breaking changes that prevent you from running B' after it

Now, my expectation was that if I ran alembic upgrade dev@head I would get the following order of executions:

A --> B --> B' --> C --> C'

With the execution sort of jumping back and forth between the main and the dev branch following a sort of "chronological" order.

However, what I'm getting is

A --> B --> C --> B' --> C'

Is there anything I can do to get A --> B --> B' --> C --> C'?

Thanks, Fernando

Answer 1

I got an answer in the Discussions section of the Alembic repo from zzzeek himself about this:

if there's no relationship between C and B' then yes it's expected that these two migrations may occur in any order. So if your migrations have an ordering requirement that C must occur after B', add this relationship using a dependency, that is, the depends_on label. see that documented section for examples, here you'd want to make C dependent on B'.

And, the mentioned docs are these