> > That being said, I think the most important consideration for now is where > are the current maintainers / contributors to the variant type. If most of > them are already PMC members / committers on a project, it becomes a bit > easier. Otherwise if there isn't much overlap with a project's existing > governance, I worry there could be a bit of friction. How many active > contributors are there from Iceberg? And how about from Arrow?
I think this is the key question. What are the requirements around governance? I've seen some tangential messaging here but I'm not clear on what everyone expects. I think for a lot of the other concerns my view is that the exact project does not really matter (and choosing a project with mature cross language testing infrastructure or committing to building it is critical). IIUC we are talking about following artifacts: 1. A stand alone specification document (this can be hosted anyplace) 2. A set of language bindings with minimal dependencies can be consumed downstream (again, as long as dependencies are managed carefully any project can host these) 3. Potential integration where appropriate into file format libraries to support shredding (but as of now this is being bypassed by using conventions anyways). My impression is that at least for Parquet there has been a proliferation of vectorized readers across different projects, so I'm not clear how much standardization in parquet-java could help here. To respond to some other questions: Arrow is not used as Spark's in-memory model, nor Trino and others so those > existing relationships aren't there. I also worry that differences in > approaches would make it difficult later on. While Arrow is not in the core memory model, for Spark I believe it is still used for IPC for things like Java<->Python. Trino also consumes Arrow libraries today to support things like Snowflake/Bigquery federation. But I think this is minor because as mentioned above I think the functional libraries would be relatively stand-alone. Do we think it could be introduced as a canonical extension arrow type? I believe it can be, I think there are probably different layouts that can be supported: 1. A struct with two variable width bytes columns (metadata and value data are stored separately and each entry has a 1:1 relationship). 2. Shredded (shredded according to the same convention as parquet), I would need to double check but I don't think Arrow would have problems here but REE would likely be required to make this efficient (i.e. sparse value support is important). In both cases the main complexity is providing the necessary functions for manipulation. Thanks, Micah On Fri, Aug 16, 2024 at 3:58 PM Will Jones <will.jones...@gmail.com> wrote: > In being more engine and format agnostic, I agree the Arrow project might > be a good host for such a specification. It seems like we want to move away > from hosting in Spark to make it engine agnostic. But moving into Iceberg > might make it less format agnostic, as I understand multiple formats might > want to implement this. I'm not intimately familiar with the state of this, > but I believe Delta Lake would like to be aligned with the same format as > Iceberg. In addition, the Lance format (which I work on), will eventually > be interesting as well. It seems equally bad to me to attach this > specification to a particular table format as it does a particular query > engine. > > That being said, I think the most important consideration for now is where > are the current maintainers / contributors to the variant type. If most of > them are already PMC members / committers on a project, it becomes a bit > easier. Otherwise if there isn't much overlap with a project's existing > governance, I worry there could be a bit of friction. How many active > contributors are there from Iceberg? And how about from Arrow? > > BTW, I'd add I'm interested in helping develop an Arrow extension type for > the binary variant type. I've been experimenting with a DataFusion > extension that operates on this [1], and already have some ideas on how > such an extension type might be defined. I'm not yet caught up on the > shredded specification, but I think having just the binary format would be > beneficial for in-memory analytics, which are most relevant to Arrow. I'll > be creating a seperate thread on the Arrow ML about this soon. > > Best, > > Will Jones > > [1] > https://github.com/datafusion-contrib/datafusion-functions-variant/issues > > > On Thu, Aug 15, 2024 at 7:39 PM Gang Wu <ust...@gmail.com> wrote: > > > + dev@arrow > > > > Thanks for all the valuable suggestions! I am inclined to Micah's idea > that > > Arrow might be a better host compared to Parquet. > > > > To give more context, I am taking the initiative to add the geometry type > > to both Parquet and ORC. I'd like to do the same thing for variant type > in > > that variant type is engine and file format agnostic. This does mean that > > Parquet might not be the neutral place to hold the variant spec. > > > > Best, > > Gang > > > > On Fri, Aug 16, 2024 at 10:00 AM Jingsong Li <jingsongl...@gmail.com> > > wrote: > > > > > Thanks all for your discussion. > > > > > > The Apache Paimon community is also considering support for this > > > Variant type, without a doubt, we hope to maintain consistency with > > > Iceberg. > > > > > > Not only the Paimon community, but also various computing engines need > > > to adapt to this type, such as Flink and StarRocks. We also hope to > > > promote them to adapt to this type. > > > > > > It is worth noting that we also need to standardize many functions > > > related to it. > > > > > > A neutral place to maintain it is a great choice. > > > > > > - As Gang Wu said, a standalone project is good, just like > RoaringBitmap > > > [1]. > > > - As Ryan said, Parquet community is a neutral option too. > > > - As Micah said, Arrow is also an option too. > > > > > > [1] https://github.com/RoaringBitmap > > > > > > Best, > > > Jingsong > > > > > > On Fri, Aug 16, 2024 at 7:18 AM Micah Kornfield <emkornfi...@gmail.com > > > > > wrote: > > > >> > > > >> Thats fair @Micah, so far all the discussions have been direct and > off > > > the dev list. Would you like to make the request on the public Spark > Dev > > > list? I would be glad to co-sign, I can also draft up a quick email if > > you > > > don't have time. > > > > > > > > > > > > I think once we come to consensus, if you have bandwidth, I think the > > > message might be better coming from you, as you have more context on > some > > > of the non-public conversations, the requirements from an Iceberg > > > perspective on governance and the blockers that were encountered. If > > > details on the conversations can't be shared, (i.e. we are starting > from > > > scratch) it seems like suggesting a new project via SPIP might be the > way > > > forward. I'm happy to help with that if it is useful but I would guess > > > Aihua or Tyler might be in a better place to start as it seems they > have > > > done more serious thinking here. > > > > > > > > If we decide to try to standardize on Parquet or Arrow I'm happy to > > help > > > support the effort in those communities. > > > > > > > > Thanks, > > > > Micah > > > > > > > > On Thu, Aug 15, 2024 at 8:09 AM Russell Spitzer < > > > russell.spit...@gmail.com> wrote: > > > >> > > > >> Thats fair @Micah, so far all the discussions have been direct and > off > > > the dev list. Would you like to make the request on the public Spark > Dev > > > list? I would be glad to co-sign, I can also draft up a quick email if > > you > > > don't have time. > > > >> > > > >> On Thu, Aug 15, 2024 at 10:04 AM Micah Kornfield < > > emkornfi...@gmail.com> > > > wrote: > > > >>>> > > > >>>> I agree that it would be beneficial to make a sub-project, the > main > > > problem is political and not logistic. I've been asking for movement > from > > > other relative projects for a month and we simply haven't gotten > > anywhere. > > > >>> > > > >>> > > > >>> I just wanted to double check that these issues were brought > directly > > > to the spark community (i.e. a discussion thread on the Spark developer > > > mailing list) and not via backchannels. > > > >>> > > > >>> I'm not sure the outcome would be different and I don't think this > > > should block forking the spec, but we should make sure that the > decision > > is > > > publicly documented within both communities. > > > >>> > > > >>> Thanks, > > > >>> Micah > > > >>> > > > >>> On Thu, Aug 15, 2024 at 7:47 AM Russell Spitzer < > > > russell.spit...@gmail.com> wrote: > > > >>>> > > > >>>> @Gang Wu > > > >>>> > > > >>>> I agree that it would be beneficial to make a sub-project, the > main > > > problem is political and not logistic. I've been asking for movement > from > > > other relative projects for a month and we simply haven't gotten > > anywhere. > > > I don't think there is anything that would stop us from moving to a > joint > > > project in the future and if you know of some way of encouraging that > > > movement from other relevant parties I would be glad to collaborate in > > > doing that. One thing that I don't want to do is have the Iceberg > project > > > stay in a holding pattern without any clear roadmap as to how to > proceed. > > > >>>> > > > >>>> On Wed, Aug 14, 2024 at 11:12 PM Yufei Gu <flyrain...@gmail.com> > > > wrote: > > > >>>>> > > > >>>>> I’m on board with copying the spec into our repository. However, > as > > > we’ve talked about, it’s not just a straightforward copy—there are > > already > > > some divergences. Some of them are under discussion. Iceberg is > > definitely > > > the best place for these specs. Engines like Trino and Flink can then > > rely > > > on the Iceberg specs as a solid foundation. > > > >>>>> > > > >>>>> Yufei > > > >>>>> > > > >>>>> On Wed, Aug 14, 2024 at 7:51 PM Gang Wu <ust...@gmail.com> > wrote: > > > >>>>>> > > > >>>>>> Sorry for chiming in late. > > > >>>>>> > > > >>>>>> From the discussion in > > > https://lists.apache.org/thread/xcyytoypgplfr74klg1z2rgjo6k5b0sq, I > > don't > > > quite understand why it is logistically complicated to create a > > sub-project > > > to hold the variant spec and impl. > > > >>>>>> > > > >>>>>> IMHO, coping the variant type spec into Apache Iceberg has some > > > deficiencies: > > > >>>>>> - It is a burden to update two repos if there is a variant type > > > spec change and will likely result in deviation if some changes do not > > > reach agreement from both parties. > > > >>>>>> - Implementers are required to keep an eye on both specs > > > (considering proprietary engines where both Iceberg and Delta are > > > supported). > > > >>>>>> - Putting the spec and impl of variant type in Iceberg repo does > > > lose the opportunity for better native support from file formats like > > > Parquet and ORC. > > > >>>>>> > > > >>>>>> I'm not sure if it is possible to create a separate project > (e.g. > > > apache/variant-type) to make it a single point of truth. We can learn > > from > > > the experience of Apache Arrow. In this fashion, different engines, > table > > > formats and file formats can follow the same spec and are free to > depend > > on > > > the reference implementations from apache/variant-type or implement > their > > > own. > > > >>>>>> > > > >>>>>> Best, > > > >>>>>> Gang > > > >>>>>> > > > >>>>>> > > > >>>>>> > > > >>>>>> > > > >>>>>> On Thu, Aug 15, 2024 at 10:07 AM Jack Ye <yezhao...@gmail.com> > > > wrote: > > > >>>>>>> > > > >>>>>>> +1 for copying the spec into our repository, I think we need to > > > own it fully as a part of the table spec, and we can build > compatibility > > > through tests. > > > >>>>>>> > > > >>>>>>> -Jack > > > >>>>>>> > > > >>>>>>> On Wed, Aug 14, 2024 at 12:52 PM Russell Spitzer < > > > russell.spit...@gmail.com> wrote: > > > >>>>>>>> > > > >>>>>>>> I'm not really in favor of linking and annotating as that just > > > makes things more complicated and still is essentially forking just > with > > > more steps. If we just track our annotations / modifications to a > single > > > commit/version then we have the same issue again but now you have to go > > to > > > multiple sources to get the actual Spec. In addition, our very copy of > > the > > > Spec is going to require new types which don't exist in the Spark Spec > > > which necessarily means diverging. We will need to take up new > primitive > > > id's (as noted in my first email) > > > >>>>>>>> > > > >>>>>>>> The other issue I have is I don't think the Spark Spec is > really > > > going through a thorough review process from all members of the Spark > > > community, I believe it probably should have gone through the SPIP but > > > instead seems to have been merged without broad community involvement. > > > >>>>>>>> > > > >>>>>>>> The only way to truly avoid diverging is to only have a single > > > copy of the spec, in our previous discussions the vast majority of > Apache > > > Iceberg community want it to exist here. > > > >>>>>>>> > > > >>>>>>>> On Wed, Aug 14, 2024 at 2:19 PM Daniel Weeks < > dwe...@apache.org > > > > > > wrote: > > > >>>>>>>>> > > > >>>>>>>>> I'm really excited about the introduction of variant type to > > > Iceberg, but I want to raise concerns about forking the spec. > > > >>>>>>>>> > > > >>>>>>>>> I feel like preemptively forking would create the situation > > > where we end up diverging because there's little reason to work with > both > > > communities to evolve in a way that benefits everyone. > > > >>>>>>>>> > > > >>>>>>>>> I would much rather point to a specific version of the spec > and > > > annotate any variance in Iceberg's handling. This would allow us to > > > continue without dividing the communities. > > > >>>>>>>>> > > > >>>>>>>>> If at any point there are irreconcilable differences, I would > > > support forking, but I don't feel like that should be the initial step. > > > >>>>>>>>> > > > >>>>>>>>> No one is excited about the possibility that the physical > > > representations end up diverging, but it feels like we're setting > > ourselves > > > up for that exact scenario. > > > >>>>>>>>> > > > >>>>>>>>> -Dan > > > >>>>>>>>> > > > >>>>>>>>> > > > >>>>>>>>> On Wed, Aug 14, 2024 at 6:54 AM Fokko Driesprong < > > > fo...@apache.org> wrote: > > > >>>>>>>>>> > > > >>>>>>>>>> +1 to what's already being said here. It is good to copy the > > > spec to Iceberg and add context that's specific to Iceberg, but at the > > same > > > time, we should maintain compatibility. > > > >>>>>>>>>> > > > >>>>>>>>>> Kind regards, > > > >>>>>>>>>> Fokko > > > >>>>>>>>>> > > > >>>>>>>>>> Op wo 14 aug 2024 om 15:30 schreef Manu Zhang < > > > owenzhang1...@gmail.com>: > > > >>>>>>>>>>> > > > >>>>>>>>>>> +1 to copy the spec into our repository. I think the best > way > > > to keep compatibility is building integration tests. > > > >>>>>>>>>>> > > > >>>>>>>>>>> Thanks, > > > >>>>>>>>>>> Manu > > > >>>>>>>>>>> > > > >>>>>>>>>>> On Wed, Aug 14, 2024 at 8:27 PM Péter Váry < > > > peter.vary.apa...@gmail.com> wrote: > > > >>>>>>>>>>>> > > > >>>>>>>>>>>> Thanks Russell and Aihua for pushing Variant support! > > > >>>>>>>>>>>> > > > >>>>>>>>>>>> Given the differences between the supported types and the > > > lack of interest from the other project, I think it is reasonable to > > > duplicate the specification to our repository. > > > >>>>>>>>>>>> I would give very strong emphasis on sticking to the Spark > > > spec as much as possible, to keep compatibility as much as possible. > > Maybe > > > even revert to a shared specification if the situation changes. > > > >>>>>>>>>>>> > > > >>>>>>>>>>>> Thanks, > > > >>>>>>>>>>>> Peter > > > >>>>>>>>>>>> > > > >>>>>>>>>>>> Aihua Xu <aihu...@gmail.com> ezt írta (időpont: 2024. > aug. > > > 13., K, 19:52): > > > >>>>>>>>>>>>> > > > >>>>>>>>>>>>> Thanks Russell for bringing this up. > > > >>>>>>>>>>>>> > > > >>>>>>>>>>>>> This is the main blocker to move forward with the Variant > > > support in Iceberg and hopefully we can have a consensus. To me, I also > > > feel it makes more sense to move the spec into Iceberg rather than > Spark > > > engine owns it and we try to keep it compatible with Spark spec. > > > >>>>>>>>>>>>> > > > >>>>>>>>>>>>> Thanks, > > > >>>>>>>>>>>>> Aihua > > > >>>>>>>>>>>>> > > > >>>>>>>>>>>>> On Mon, Aug 12, 2024 at 6:50 PM Russell Spitzer < > > > russell.spit...@gmail.com> wrote: > > > >>>>>>>>>>>>>> > > > >>>>>>>>>>>>>> Hi Y’all, > > > >>>>>>>>>>>>>> > > > >>>>>>>>>>>>>> We’ve hit a bit of a roadblock with the Variant > Proposal, > > > while we were hoping to move the Variant and Shredding specifications > > from > > > Spark into Iceberg there doesn’t seem to be a lot of interest in that. > > > Unfortunately, I think we have a number of issues with just linking to > > the > > > Spark project directly from within Iceberg and I believe we need to > copy > > > the specifications into our repository. > > > >>>>>>>>>>>>>> > > > >>>>>>>>>>>>>> There are a few reasons why i think this is necessary > > > >>>>>>>>>>>>>> > > > >>>>>>>>>>>>>> First, we have a divergence of types already. The Spark > > > Specification already includes types which Iceberg has no definition > for > > > (19, 20 - Interval Types) and Iceberg already has a type which is not > > > included within the Spark Specification (Time) and will soon have more > > with > > > TimestampNS, and Geo. > > > >>>>>>>>>>>>>> > > > >>>>>>>>>>>>>> Second, We would like to make sure that Spark is not a > > hard > > > dependency for other engines. We are working with several implementers > of > > > the Iceberg spec and it has previously been agreed that it would be > best > > if > > > the source of truth for Variant existed in an engine and file format > > > neutral location. The Iceberg project has a good open model of > governance > > > and, as we have seen so far discussing Variant, open and active > > > collaboration. This would also help as we can strictly version our > > changes > > > in-line with the rest of the Iceberg spec. > > > >>>>>>>>>>>>>> > > > >>>>>>>>>>>>>> Third, The Shredding spec is not quite finished and > > > requires some group analysis and discussion before we commit it. I > think > > > again the Iceberg community is probably the right place for this to > > happen > > > as we have already started discussions here on these topics. > > > >>>>>>>>>>>>>> > > > >>>>>>>>>>>>>> For these reasons I think we should go with a direct > copy > > > of the existing specification from the Spark Project and move ahead > with > > > our discussions and modifications within Iceberg. That said, I do not > > want > > > to diverge if possible from the Spark proposal. For example, although > we > > do > > > not use the Interval types above, I think we should not reuse those > type > > > ids within our spec. Iceberg's Variant Spec types 19 and 20 would > remain > > > unused along with any other types we think are not applicable. We > should > > > strive whenever possible to allow for compatibility. > > > >>>>>>>>>>>>>> > > > >>>>>>>>>>>>>> In the interest of moving forward with this proposal I > am > > > hoping to see if anyone in the community objects to this plan going > > forward > > > or has a better alternative. > > > >>>>>>>>>>>>>> > > > >>>>>>>>>>>>>> As always I am thankful for your time and am eager to > hear > > > back from everyone, > > > >>>>>>>>>>>>>> Russ > > > >>>>>>>>>>>>>> > > > >>>>>>>>>>>>>> > > > > > >
