What do people think about using the C interface representation? On Sun, Dec 29, 2019 at 12:42 PM Micah Kornfield <emkornfi...@gmail.com> wrote:
> I opened https://github.com/google/flatbuffers/issues/5688 to try to get > some clarity. > > On Tue, Dec 24, 2019 at 12:13 PM Wes McKinney <wesmck...@gmail.com> wrote: > > > On Tue, Dec 24, 2019 at 2:47 AM Micah Kornfield <emkornfi...@gmail.com> > > wrote: > > >> > > >> If we were to make the same kinds of forward/backward compatibility > > >> guarantees as with Flatbuffers it could create a lot of work for > > >> maintainers. > > > > > > Does it pay to follow-up with the flatbuffer project to understand if > > the forward/backward compatibility guarantees the flatbuffers provide > > extend to their JSON format? > > > > I spent a few minutes looking at the Flatbuffers codebase and > > documentation and did not find anything, so this seems like useful > > information to have regardless. > > > > > > > > On Sun, Dec 15, 2019 at 11:17 AM Wes McKinney <wesmck...@gmail.com> > > wrote: > > >> > > >> I'd be open to looking at a proposal for a human-readable text > > >> representation, but I'm definitely wary about making any kind of > > >> cross-version compatibility guarantees (beyond "we will do our best"). > > >> If we were to make the same kinds of forward/backward compatibility > > >> guarantees as with Flatbuffers it could create a lot of work for > > >> maintainers. > > >> > > >> On Thu, Dec 12, 2019 at 12:43 AM Micah Kornfield < > emkornfi...@gmail.com> > > wrote: > > >> > > > >> > > > > >> > > With these two together, it would seem not too difficult to create > > a text > > >> > > representation for Arrow schemas that (at some point) has some > > >> > > compatibility guarantees, but maybe I'm missing something? > > >> > > > >> > > > >> > I think the main risk is if somehow flatbuffers JSON parsing doesn't > > handle > > >> > backward compatible changes to the arrow schema message. Given the > > way the > > >> > documentation is describing the JSON functionality I think this > would > > be > > >> > considered a bug. > > >> > > > >> > The one downside to calling the "schema" canonical is the > flatbuffers > > JSON > > >> > functionality only appears to be available in C++ and Java via JNI, > > so it > > >> > wouldn't have cross language support. I think this issue is more > one > > of > > >> > semantics though (i.e. does the JSON description become part of the > > "Arrow > > >> > spec" or does it live as a C++/Python only feature). > > >> > > > >> > -Micah > > >> > > > >> > > > >> > On Tue, Dec 10, 2019 at 10:51 AM Christian Hudon < > > chr...@elementai.com> > > >> > wrote: > > >> > > > >> > > Micah: I didn't know that Flatbuffers supported serialization > > to/from JSON, > > >> > > thanks. That seems like a very good start, at least. I'll aim to > > create a > > >> > > draft pull request that at least wires everything up in Arrow so > we > > can > > >> > > load/save a Schema.fbs instance from/to JSON. At least it'll make > > it easier > > >> > > for me to see how Arrow schemas would look in JSON with that. > > >> > > > > >> > > Otherwise, I'm still gathering requirements internally here. For > > example, > > >> > > one thing that would be nice would be to be able to output a JSON > > Schema > > >> > > from at least a subset of the Arrow schema. (That way our users > > could start > > >> > > by passing around JSON with a given schema, and transition pieces > > of a > > >> > > workflow to Arrow as they're ready.) But that part can also be > done > > outside > > >> > > of the Arrow code, if deemed not relevant to have in the Arrow > > codebase > > >> > > itself. > > >> > > > > >> > > One core requirement for us, however, would be eventual > > compatibility > > >> > > between Arrow versions for a given text representation of a > schema. > > >> > > Meaning, if you have a text description of a given Arrow schema, > > you can > > >> > > load it into different versions of Arrow and it creates a valid > > Schema > > >> > > Flatbuffer description, that Arrow can use. Wes, were you thinking > > of that, > > >> > > or of something else, when you wrote "only makes sense if it is > > offered > > >> > > without any backward/forward compatibility guarantees"? > > >> > > > > >> > > For the now, or me, assuming the JSON serialization done by the > > Flatbuffer > > >> > > libraries is usable, it seems we have all the pieces to make this > > happen: > > >> > > 1) The binary Schema.fbs data structures has to be compatible > > between > > >> > > different versions of Arrow, otherwise two processes with > different > > Arrow > > >> > > versions won't be able to interoperate, no? > > >> > > 2) The Flatbuffer <-> JSON serialization supplied by the > Flatbuffers > > >> > > library also has to be compatible between different versions of > the > > >> > > Flatbuffers library, since the main use case seems to be storing > > >> > > Flatbuffers assets into version control. Breaking changes there > > will also > > >> > > be painful to their users. > > >> > > > > >> > > With these two together, it would seem not too difficult to create > > a text > > >> > > representation for Arrow schemas that (at some point) has some > > >> > > compatibility guarantees, but maybe I'm missing something? > > >> > > > > >> > > Thanks, > > >> > > > > >> > > Christian > > >> > > > > >> > > Le lun. 9 déc. 2019, à 07 h 00, Wes McKinney <wesmck...@gmail.com > > > > a > > >> > > écrit : > > >> > > > > >> > > > The only "canonical" representation of schemas at the moment is > > the > > >> > > > Flatbuffers data structure [1] > > >> > > > > > >> > > > Having a human-readable/parseable text representation I think > only > > >> > > > makes sense if it is offered without any backward/forward > > >> > > > compatibility guarantees. > > >> > > > > > >> > > > Note I had previously opened > > >> > > > https://issues.apache.org/jira/browse/ARROW-3730 where I noted > > that > > >> > > > there's no way (aside from generating the Flatbuffers messages) > to > > >> > > > generate a schema representation that can be used later to > > reconstruct > > >> > > > a schema in a program. If such a representation were human > > >> > > > readable/editable that seems beneficial. > > >> > > > > > >> > > > > > >> > > > > > >> > > > [1]: > > https://github.com/apache/arrow/blob/master/format/Schema.fbs > > >> > > > > > >> > > > On Sat, Dec 7, 2019 at 11:56 AM Maarten Ballintijn < > > maart...@xs4all.nl> > > >> > > > wrote: > > >> > > > > > > >> > > > > > > >> > > > > Is there a syntax specified for schemas? > > >> > > > > > > >> > > > > Cheers, > > >> > > > > Maarten. > > >> > > > > > > >> > > > > > > >> > > > > > On Dec 6, 2019, at 5:01 PM, Micah Kornfield < > > emkornfi...@gmail.com> > > >> > > > wrote: > > >> > > > > > > > >> > > > > > Hi Christian, > > >> > > > > > As far as I know no-one is working on a canonical text > > representation > > >> > > > for > > >> > > > > > schemas. A JSON serializer exists for integration test > > purposes, but > > >> > > > > > IMO it shouldn't be relied upon as canonical. > > >> > > > > > > > >> > > > > > It looks like Flatbuffers supports serialization to/from > JSON > > [1 > > >> > > > > > < > > https://google.github.io/flatbuffers/flatbuffers_guide_use_cpp.html > > >> > > > >], > > >> > > > > > using that functionality might be a promising avenue to > > pursue for a > > >> > > > human > > >> > > > > > readable schema. I could see adding a helper method > someplace > > under > > >> > > > IPC for > > >> > > > > > this. Would that meet your needs? I think if there are > other > > >> > > > > > requirements, then a proposal would be welcome. Ideally, a > > solution > > >> > > > would > > >> > > > > > not require additional build/runtime dependencies. > > >> > > > > > > > >> > > > > > > > >> > > > > > Thanks, > > >> > > > > > Micah > > >> > > > > > > > >> > > > > > [1] See Text & schema parsing > > >> > > > > > > > https://google.github.io/flatbuffers/flatbuffers_guide_use_cpp.html > > >> > > > > > > > >> > > > > > On Fri, Dec 6, 2019 at 1:26 PM Christian Hudon < > > chr...@elementai.com > > >> > > > > > >> > > > wrote: > > >> > > > > > > > >> > > > > >> Hi, > > >> > > > > >> > > >> > > > > >> For the uses I would like to make of Arrow, I would need a > > >> > > > human-readable > > >> > > > > >> and -writable version of an Arrow Schema, that could be > > converted to > > >> > > > and > > >> > > > > >> from the Arrow Schema C++ object. Going through the doc for > > 0.15.1, > > >> > > I > > >> > > > don't > > >> > > > > >> see anything to that effect, with the closest being the > > ToString() > > >> > > > method > > >> > > > > >> on DataType instances, but which is meant for debugging > > only. (I > > >> > > need > > >> > > > an > > >> > > > > >> expression of an Arrow Schema that people can read, and > that > > can > > >> > > live > > >> > > > > >> outside of the code for a particular operation.) > > >> > > > > >> > > >> > > > > >> Is a text representation of an Arrow Schema something that > > is being > > >> > > > worked > > >> > > > > >> on now? If not, would you folks be interested in me putting > > up an > > >> > > > initial > > >> > > > > >> proposal for discussion? Any design constraints I should > pay > > >> > > > attention to, > > >> > > > > >> then? > > >> > > > > >> > > >> > > > > >> Thanks, > > >> > > > > >> > > >> > > > > >> Christian > > >> > > > > >> -- > > >> > > > > >> > > >> > > > > >> > > >> > > > > >> │ Christian Hudon > > >> > > > > >> > > >> > > > > >> │ Applied Research Scientist > > >> > > > > >> > > >> > > > > >> Element AI, 6650 Saint-Urbain #500 > > >> > > > > >> > > >> > > > > >> Montréal, QC, H2S 3G9, Canada > > >> > > > > >> Elementai.com > > >> > > > > >> > > >> > > > > > > >> > > > > > >> > > > > >> > > > > >> > > -- > > >> > > > > >> > > > > >> > > │ Christian Hudon > > >> > > > > >> > > │ Applied Research Scientist > > >> > > > > >> > > Element AI, 6650 Saint-Urbain #500 > > >> > > > > >> > > Montréal, QC, H2S 3G9, Canada > > >> > > Elementai.com > > >> > > > > >
