Add support of citext to MissingUniqueIndexChecker

[djezzzl]

No description provided.

[pirj]

Does it make sense to revive this PR now?

[djezzzl]

@pirj, we can revive it, although, we should distinguish cases where your fix was applied from the rest. Could you please help how we can do that?

[pirj]

I'd say two things would affect the checker's decision:

1. Rails version. Depending on if the fix will be backported or not. Older versions would add LOWER() to queries. Newer won't.
2. presence of LOWER() on the uniqueness index.

So, the inspector should log an error:
a) for older Rails versions when there's no LOWER() on the index
b) for newer Rails versions when there's LOWER() functional specification on the index

Does this make sense, or am I missing something?

[djezzzl]

It makes total sense to me. Do we have a better way of relying on instead of the Rails version?

[djezzzl]

I'm not sure we can simply say the version is greater/lower.

[pirj]

We depend on Active Record in runtime, so we can reasonably compare it:

> ActiveRecord.version > Gem::Version.new('6.0.4')
=> true
> ActiveRecord.version > Gem::Version.new('6.0.6')
=> false

Let's see when the fix is released to build a uses_lower_in_uniqueness_validation_queries? helper method correctly.

[djezzzl]

Sounds like a plan to me.