Make ordered as the default behavior

[wookayin]

map() preserving the order is much more intuitive behavior. Python's builtin Pool executor, ray, joblib, etc. all work in such a way.

I realized that one can still pipe to pl.process.ordered, but the documentation is limited and this is quite difficult to use.

def slow_identity(x):
   time.sleep(random.random())
   return x

s = list(range(100)) | pl.process.map(slow_identity, workers=N)
list(s)     # should be ordered by default

[cgarciae]

Hey @wookayin,

Implementing ordering efficiently can get very tricky if you consider multi-stage pipelines containing transformations like filter and flat_map. The current implementation of ordered is pessimistic and has to wait for all the elements to come in before yielding.

I think the example from the ordered documentation should be able for people to get started, but would be happy to improve if you give some feedback.

[cgarciae]

I don't agree that stages should order by default since its a slower operation. We can optimize ordered for simple cases and add ordered shortcut flag to map.

What do you think?

[gtadamson]

I agree with @cgarciae that ordering by default would be undesirable if it slowed down the speed of the full pypeln