Image promote does not check for duplicate names

[askfongjojo]

I was able to promote an image with the same name as another image that exists at the silo-level. It should probably complain about name duplication.

[zephraph]

I'm surprised about this given the unique index constraint on silo_id, project_id, and name. My expectation is that the update should fail if it violates that unique index.

Regardless, I'll dig deeper into it.

[davepacheco]

I suspect what's going on is that you've got two items in the index both having (silo_id, NULL project_id, name), but the two NULL values act as though they're distinct. Check this out:
https://www.cockroachlabs.com/docs/stable/null-handling.html#nulls-and-unique-constraints

It may be clearer to have two different partial indexes, one for project-level uniqueness and one for silo-level uniqueness. I'm not sure but I think it's a good idea to leave NULL values out of indexes.

[zephraph]

That's unfortunate. I'll put a PR.