add support for polars >= 0.8

[wseaton]

Currently connectorx pins the version of polars to 0.8.*, but it's possible to add support for later versions of polars without breaking backwards compatibility by just attempting the import and catching the exception. What do y'all think? I'm also open to a ranged dependency, something like >=0.8,<0.11 that we could simply increment if there are no additional API breaks.

(cc @ritchie46)

[dovahcrow]

@wseaton What is the guarantee for the version number in Polars? In Semver it only guarantees no breaking changes between 0.x.y and 0.x.z, but not between 0.x and 0.y. If Polars has a different guarantee, e.g. no breaking changes until 1.0, we could definitely do >=0.8.

I'm worrying that catching the exception for the import is not enough.

[wseaton]

@dovahcrow good point, I think I'd defer to @ritchie46 on any future plans for change. The from_arrow API is one of the most foundational APIs of the library, so I'd hope it wouldn't be changing any more between versions and can be considered 'settled code'.

As for the brittleness of the import shim, a polars 1.0 user could just use return_type='arrow' as a workaround if this in the future was to ever break so there's at least an escape hatch.

[dovahcrow]

@dovahcrow good point, I think I'd defer to @ritchie46 on any future plans for change. The from_arrow API is one of the most foundational APIs of the library, so I'd hope it wouldn't be changing any more between versions and can be considered 'settled code'.

As for the brittleness of the import shim, a polars 1.0 user could just use return_type='arrow' as a workaround if this in the future was to ever break so there's at least an escape hatch.

Sounds good to me for ">=0.8" if from_arrow is considered settled.

[ritchie46]

Polars has breaking changes on the x in 0.x.y. That said, the API is stabilizing and I cannot imagine pl.from_arrow to be deprecated. Given that version 0.8 is pretty old (in Polars lifetime 😄), I'd only support a more recent version.

[dovahcrow]

Let's merge this PR then. I think from_arrow is the only function we require from Polars.