Generalize in_

[tysonzero]

The current type is:

in_ :: (Functor f, Foldable f) => f (Field a) -> Field a -> Field SqlBool

But it seems like a nicer type would be:

in_ :: (Default EqPP fields fields, Foldable f) => f fields -> fields -> Field SqlBool

We can drop the Functor as the mapping is/can-be done after the toList/foldr type stuff, and we take advantage of the Default EqPP machinery that .=== uses since IN seems to work just fine in PostgreSQL on products/tuples.

This should close #404, #406, #419 and the issue is mentioned in open issues #431 and #599.

[tomjaguarpaw]

This seems like a good idea. Is it a breaking change? If so it would prefer to introduce it under a new name first, but I'm struggling to think of any code that could be broken by this.

[ocharles]

Anything that wraps in_ and has a type signature (myIn = in_) would break, because the type has changed. It's hypothetical, but probably a better path than trying to find a threshold of "realistic" breaks

[ocharles]

Oh wait, maybe I'm wrong because Field a has that instance? Might be worth checking that one,

[tysonzero]

Yes Field a does have that instance. Should be a strict generalization, so only breakage I can think of would be if it leads to type ambiguity or if someone's using TypeApplications on it.

[tomjaguarpaw]

@tysonzero: can you confirm whether this does the job? #604

[tysonzero]

@tomjaguarpaw

It'd be nice to drop the Functor constraint so it can work on Set and similar. Similarly in in_ the Functor constraint isn't even used at all, F.toList is called immediately on the input.

I'm not sure if there will be any performance difference using ors instead of the literal multi-column in operator, if the optimizer is smart in theory it hopefully will work the same, but worth considering.

[tomjaguarpaw]

Oh yeah, thanks. Please take another look: #604

(Regarding performance, let's leave that as a potential future optimization. I don't want to get into the weeds of that.)

[tysonzero]

Then yes that seems reasonable!

[tomjaguarpaw]

Thanks for your input. If Opaleye contains blockers for you or even stuff that you find just unergonomic then please keep prompting me about it.