Unneeded Change Added to Migration

[JEG2]

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Versions

Erlang: 28.0.2
Elixir: 1.18.4-otp-28
Ash: 3.5.37
AshPostgreSQL: 2.6.17

Operating system

macOS Sequoia 15.6.1

Current Behavior

While reading Chapter 2 of the Ash Framework book, I noticed that ash.codegen generated a slightly more verbose migration than was strictly needed:

JEG2/tunez@e19a905#diff-38665c31e93a41d7132c1bff9af04ecb4c757bfd15758d22a5839e64d6d24752

It looks like it is removing a foreign key only to reset it to the same value.

Rebecca Le asked me to open this issue.

Reproduction

This is the code I added before invoking the generator:

JEG2/tunez@e19a905#diff-11818765a97af826d1ca632b019da6be529cbdd9af6f4d2c2231405dec15dccbR64-R67

Expected Behavior

I think it would be enough just to create and drop the index for this change.

[WillG2001]

If I'm understanding correctly, the only real change needed is to create or drop the index, since dropping and re-adding the foreign key is unnecessary and noisy. I'm in the process of putting together a PR for this issue, and just wanted to make sure I'm not missing anything. I updated the migration generator so it can tell when the only thing that changed on a reference is the index? setting. In that case it should:

1. Emit the right index change (create index or drop index).
2. Not emit any foreign key drop or re-add.

So for “only the index changed” you get a small migration that only touches the index, which matches what you’d expect.

[zachdaniel]

Yes, that sounds right to me! 🥳