Discrete cleanup

[Earlopain]

• v4_ready? can always return true on v4. Deprecation?
• Nothing checks against discrete_support?/is_discrete? anymore
• Benchmark to compare the two doesn't do anything anymore
• Remove some duplicated tests now that they both do the same
• Ignore the is_discrete. I don't believe this can safely be dropped beforehand. Probably a v5 thing.

[bensheldon]

Thanks for doing this! This is great!

v4_ready? can always return true on v4. Deprecation?

Yes, I think returning true on v4, and adding a deprecation warning to get people to remove it would be good.

[Earlopain]

Alright, added a deprecation for that.

Should I skip ignored_columns for is_discrete for now? I saw you added that as a task for 4.99 in #1407.

[bensheldon]

This looks really good. Thank you for this!

Should I skip ignored_columns for is_discrete for now?

I think let's leave it.

I am a little reluctant to have ignored_columns because it changes the SQL queries from a SELECT * to explicit columns (but maybe that's good? but still different), but I don't see a safe way to only add it solely in a x.99 transitional release (because that only allows for a code change, or a migration change, but not both at the same time).

[Earlopain]

Yeah, I can see where you're coming from with that. All the additional features introduced previously were nicely guarded behind column checks and whatnot which should be sufficient.

Crossing my finders that you won't have to come back to this one for quite a while yet