Feature: run evolutions from sbt

[Stewart Stewart]

This feature is simple enough. I'd like a task in sbt that can run evolutions.

At present, evolutions are typically run by (1) making sure the app compiles, (2) running the app, (3) visiting the app from a browser.

None of those three seem necessary. Am I missing something? With those requirements, it's possible to enter a state where the code generated for Slick is wrong and preventing the app from compiling and the fix is an evolution.

What steps would need to be taken to implement this?

[Will Sargent]

Hi Stewart,

The play evolutions module is here:

https://github.com/playframework/playframework/tree/master/framework/src/play-jdbc-evolutions/src

and the module binding is here:

https://github.com/playframework/playframework/blob/master/framework/src/play-jdbc-evolutions/src/main/scala/play/api/db/evolutions/EvolutionsModule.scala#L16

The behavior of Evolutions comes out of the fact that it's loaded at runtime with the application.

If you want a decoupled solution, I would check out Flyways.  There's an example application here:

https://github.com/wsargent/play-slick-3.0

that will work even in the case where the application itself is broken.

Will.

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[Stewart Stewart]

Thanks, Will! I'll dig into this.

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[Stewart Stewart]

The main feature I'm interested preserving is Play's ability to run the appropriate downs and ups when you switch to a different branch. Is this not already a feature of Flyway?

[Will Sargent]

I haven't used Flyways in a branching long-term environment, so I don't know if they have that feature.  You can ask Boxfuse and check their documentation:

* https://flywaydb.org/documentation/

* https://flywaydb.org/support/

Will.

[Stewart Stewart]

I had a look earlier today. That doesn't seem to be the case.

[Naftoli Gugenheim]

Flyway does not support down migrations, as a matter of principle.
However, if you're using H2, you can just close all connections to the database and copy a backup file over it (made by just copying the database file), so I don't find it to be an issue.
If you're using postgresql, run it in docker and taking a snapshot should be as simple as doing `docker commit `.
And I think they're right that in production you shouldn't use downs.