It might help this discussion and future discussions like it if we could define how it is determined whether a type should be part of the Arrow format, an extension type (and what does it mean to say there is a "canonical" extension type), or just something that a language implementation or downstream library builds for itself with metadata. I feel like this has come up before but I don't recall a resolution.
Examples might also help: are there examples of "canonical extension types"? Neal On Thu, Jun 10, 2021 at 4:20 PM Micah Kornfield <emkornfi...@gmail.com> wrote: > > > > My understanding is that it means having COMPLEX as an entry in the > > arrow/type_fwd.h Type enum. I agree this would make implementation > > work in the C++ library much more straightforward. > > One idea I proposed would be to do that, and implement the > > serialization of the complex metadata using Extension types. > > > If this is a maintainable strategy for Canonical types it sounds good to > me. > > On Thu, Jun 10, 2021 at 4:02 PM Wes McKinney <wesmck...@gmail.com> wrote: > > > My understanding is that it means having COMPLEX as an entry in the > > arrow/type_fwd.h Type enum. I agree this would make implementation > > work in the C++ library much more straightforward. > > > > One idea I proposed would be to do that, and implement the > > serialization of the complex metadata using Extension types. > > > > On Thu, Jun 10, 2021 at 5:47 PM Weston Pace <weston.p...@gmail.com> > wrote: > > > > > > > While dedicated types are not strictly required, compute functions > > would > > > > be much easier to add for a first-class dedicated complex datatype > > > > rather than for an extension type. > > > @pitrou > > > > > > This is perhaps a naive question (and admittedly, I'm not up to speed > > > on my compute kernels) but why is this the case? For example, if > > > adding a complex addition kernel it seems we would be talking about... > > > > > > dest_scalar.real = scalar1.real + scalar2.real; > > > dest_scalar.im = scalar1.im + scalar2.im; > > > > > > vs... > > > > > > dest_scalar[0] = scalar1[0] + scalar2[0]; > > > dest_scalar[1] = scalar1[1] + scalar2[1]; > > > > > > On Thu, Jun 10, 2021 at 11:27 AM Wes McKinney <wesmck...@gmail.com> > > wrote: > > > > > > > > I'd be supportive of starting with this as a "canonical" extension > > > > type so that all implementations are not expected to support complex > > > > types — this would encourage us to build sufficient integration e.g. > > > > with NumPy to get things working end-to-end with the on-wire > > > > representation being an extension type. We could certainly choose to > > > > treat the type as "first class" in the C++ library without it being > > > > "top level" in the Type union in Flatbuffers. > > > > > > > > I agree that the use cases are more specialized, and the fact that we > > > > haven't needed it until now (or at least, its absence suggests this) > > > > shows that this is the case. > > > > > > > > On Thu, Jun 10, 2021 at 4:17 PM Micah Kornfield < > emkornfi...@gmail.com> > > wrote: > > > > > > > > > > > > > > > > > I'm convinced now that first-class types seem to be the way to > go > > and I'm > > > > > > happy to take this approach. > > > > > > > > > > I agree from an implementation effort it is simpler, but I'm still > > not > > > > > convinced that we should be adding this as a first class type. As > > noted in > > > > > the survey below it appears Complex numbers are not a core concept > > in many > > > > > general purpose coding languages and it doesn't appear to be a > > common type > > > > > in SQL systems either. > > > > > > > > > > The reason why I am being nit-picky here is I think that having a > > first > > > > > class type indicates that it should eventually be supported by all > > > > > reference implementations. An "well known" extension type I think > > offers > > > > > less guarantees which makes it seem more suitable for niche types. > > > > > > > > > > > I don't immediately see a Packed Struct type. Would this need to > be > > > > > > > implemented? > > > > > > Not necessarily (*). But before thinking about implementation, > > this > > > > > > proposal must be accepted into the format. > > > > > > > > > > > > > > > Yes, this is a type that has been proposed in the past and I think > > handles > > > > > a lot of types not yet in Arrow but have been requested (e.g. IP > > > > > Addresses, Geo coordinates), etc. > > > > > > > > > > On Thu, Jun 10, 2021 at 1:06 AM Simon Perkins < > > simon.perk...@gmail.com> > > > > > wrote: > > > > > > > > > > > On Wed, Jun 9, 2021 at 7:56 PM Antoine Pitrou < > anto...@python.org> > > wrote: > > > > > > > > > > > > > > > > > > > > Le 09/06/2021 à 17:52, Micah Kornfield a écrit : > > > > > > > > > > > > > > > > Adding a new first-class type in Arrow requires working > > integration > > > > > > tests > > > > > > > > between C++ and Java libraries (once the idea is informally > > agreed > > > > > > upon) > > > > > > > > and then a final vote for approval. We haven't formalized > > extension > > > > > > > types > > > > > > > > but I imagine a similar cross language requirement would be > > agreed > > > > > > upon. > > > > > > > > Implementation of computation wouldn't be required for adding > > a new > > > > > > type. > > > > > > > > Different language bindings have taken different approaches > on > > how much > > > > > > > > additional computational elements are packaged in them. > > > > > > > > > > > > > > While dedicated types are not strictly required, compute > > functions would > > > > > > > be much easier to add for a first-class dedicated complex > > datatype > > > > > > > rather than for an extension type. > > > > > > > > > > > > > > Since complex numbers are quite common in some domains, and > > since they > > > > > > > are conceptually simply, IMHO it would make sense to add them > to > > the > > > > > > > native Arrow datatypes (at least COMPLEX64 and COMPLEX128). > > > > > > > > > > > > > > > > > > > I'm convinced now that first-class types seem to be the way to > go > > and I'm > > > > > > happy to take this approach. > > > > > > Regarding compute functions, it looks like the standard set of > > scalar > > > > > > arithmetic and reduction functionality > > > > > > is desirable for complex numbers: > > > > > > https://arrow.apache.org/docs/cpp/compute.html# > > > > > > Perhaps it would be better to split the addition of the Types and > > addition > > > > > > Compute functionality into separate PRs? > > > > > > > > > > > > Regarding the process for managing this PR, it sounds like a > > proposal must > > > > > > be voted on? > > > > > > i.e. is this proposal still in this phase > > > > > > > > > http://arrow.apache.org/docs/developers/contributing.html#before-starting > > > > > > Regards > > > > > > > > > > > > Simon > > > > > > > > >
