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 >> > >
