Ugh, I think I sent from the wrong email address and my reply didn't go through.
Other people have covered the same things here, except for one point: the Avro spec states that readers that don't support an annotation are required to ignore it <https://avro.apache.org/docs/1.11.1/specification/#logical-types>. So the behavior to read either date or int correctly is inherited from the Avro spec. Ryan On Thu, May 21, 2026 at 10:17 AM Kevin Liu <[email protected]> wrote: > I wasn’t aware of the previous back-and-forth changes to this line in the > spec. Thanks for the extra context! > > A couple of points I want to align on: > 1. All implementations except Go, including Java, Python, and Rust, write > the day transform result as an Iceberg date type. That maps to the Avro > date type and is serialized as { "type": "int", "logicalType": "date" }. > 2. The Go implementation writes the day transform result an Iceberg int > type. That maps to the Avro int type and is serialized as { "type": "int" }. > 3. Java, Python, and Rust can read Avro manifest partition values as > either an Avro int type or an Avro date type. > 4. The Go implementation can currently read Avro manifest partition values > only as an Avro int type. This is the original issue that sparked this > conversation. > > Since the spec has gone back and forth between writing this as an Iceberg > int and an Iceberg date, I think readers must accept both. We can include > that as an implementation note. > > I support changing the spec back to date so it matches the default > behavior for day partition values in our implementations. Go is also > making the change to write date instead of int. > The other approach, updating all implementations to match the current > spec, would be a lot of work for little value. > > Hopefully this is the last time we make this change to the spec :) > Would love to hear from others. > > Best, > Kevin Liu > > On Wed, May 20, 2026 at 10:39 AM Fokko Driesprong <[email protected]> > wrote: > >> > It wouldn't be the first time we've retroactively updated the spec when >> finding inconsistencies with the current implementations :P >> >> I think generally we try to avoid this, but in this case it was changed >> to few times :P Maybe we should revert the spec change: >> >> >> https://github.com/apache/iceberg/pull/5980/changes#diff-36347a47c3bf67ea2ef6309ea96201814032d21bb5f162dfae4045508c15588a >> >> Curious to hear what other think. >> >> Kind regards, >> Fokko >> >> >> On 2026/05/20 17:24:22 Matt Topol wrote: >> > It wouldn't be the first time we've retroactively updated the spec >> > when finding inconsistencies with the current implementations :P >> > >> > Particularly, in this case even the "reference implementation" (i.e. >> > Java) is technically not spec-compliant since the spec says that it >> > should be an "int", not an Avro "date" type. If all the >> > implementations currently write a "date" type, then it's silly to have >> > to say that every implementation is violating the spec. >> > >> > If we want the spec to say it should be an int, but tolerate reading >> > an Avro "date" type, that's fine. But that would mean we should update >> > Java, Rust, and PyIceberg to all write plain "int" and no longer write >> > the "date" type, again: it would be silly to say that the reference >> > implementation and 2 other implementations are not following the spec. >> > :P >> > >> > I agree that it would be a big change for little value to update the >> > implementations, so my opinion is that the spec should be updated to >> > either say that "either" is allowed to be written, or that "date" >> > should be written but "int" should be allowed to be read. >> > >> > --Matt >> > >> > On Wed, May 20, 2026 at 1:05 PM Fokko Driesprong <[email protected]> >> wrote: >> > > >> > > Thanks for the quick PR Andrei. >> > > >> > > The problem is that the note conflicts with the Avro/Iceberg types >> table: https://iceberg.apache.org/spec/#avro >> > > >> > > I don't think we want to update the implementations as I agree that >> it would be a big change for little value. At the same time, I don't think >> we can retroactively update the spec. Maybe an implementation note would be >> a better solution to halt the tradition? >> > > >> > > Kind regards, >> > > Fokko >> > > >> > > >> > > On 2026/05/20 16:49:29 Andrei Tserakhau via dev wrote: >> > > > Thanks Fokko, the historical context! >> > > > >> > > > Quick check that we're aligned, since I think we may be closer than >> > > > it reads: >> > > > >> > > > My PR leaves the result type table as `int` -- no change to the >> > > > transform table, no impact on hour/month/etc., no change to the >> > > > type model. >> > > > >> > > > What the PR clarifies is the Avro encoding used when serializing a >> > > > `day` partition field into a manifest. Empirically today, Java, >> > > > PyIceberg, and Rust all write `{ "type": "int", "logicalType": >> "date" }` >> > > > there (TypeToSchema in Java, DayTransform.result_type in PyIceberg, >> > > > Transform::Day.result_type in Rust all produce a Date). Only >> > > > iceberg-go produces plain Avro `int`. The PR codifies the de facto >> > > > writer behavior as SHOULD and makes reader tolerance MUST. >> > > > >> > > > If your "stick with int" also covers the Avro annotation, then we'd >> > > > effectively be reverting three writers and orphaning every existing >> > > > manifest, which I don't think decent path, it's quite a big change >> > > > for small benefits. >> > > > >> > > > Either way, super happy to adjust the spec adjustment, the goal is >> to >> > > > stop this tradition of re-litigating issue every year, by misreading >> > > > this part of the spec. >> > > > >> > > > Best, >> > > > Andrei >> > > > >> > > > On Wed, May 20, 2026 at 6:37 PM Fokko Driesprong <[email protected]> >> wrote: >> > > > >> > > > > Thanks for briging this up Kevin, a gift that keeps on giving :) >> > > > > >> https://github.com/apache/iceberg/issues/10616#issuecomment-2200191427 >> > > > > >> > > > > 1. I think we should stick with the int type as defined in the >> spec. >> > > > > 2. It feels to me that some readers are more permissive here than >> others. >> > > > > I believe some allow reading date as an int without throwing. >> Practically, >> > > > > readers should read both. >> > > > > 3. Unfortunally, I think this is water under the bridge. As shown >> above in >> > > > > the GitHub Issue, we went back and forth, so I don't see a lot of >> value in >> > > > > switching this to date. All OSS implementations handle this as an >> int >> > > > > internally, and this also aligns with hour/month/etc. >> > > > > >> > > > > Hope this historical context helps. >> > > > > >> > > > > Kind regards, >> > > > > Fokko >> > > > > >> > > > > >> > > > > On 2026/05/20 16:33:51 Andrei Tserakhau via dev wrote: >> > > > > > Here is a fast follow with a PR: >> > > > > > https://github.com/apache/iceberg/pull/16446 >> > > > > > >> > > > > > Best, >> > > > > > Andrei >> > > > > > >> > > > > > On Wed, May 20, 2026 at 6:11 PM Andrei Tserakhau < >> > > > > > [email protected]> wrote: >> > > > > > >> > > > > > > Thanks for raising this, Kevin. >> > > > > > > >> > > > > > > Speaking as an iceberg-go maintainer, even though Go is the >> > > > > > > implementation that has to move, I'd vote: >> > > > > > > >> > > > > > > 1. Writers SHOULD emit { "type": "int", "logicalType": "date" >> }. >> > > > > > > 2. Readers MUST accept both plain `int` and `int` annotated >> with >> > > > > > > `logicalType: date`. >> > > > > > > 3. Keep the transform result type table as-is (`int` as the >> logical >> > > > > > > Iceberg type). Don't change it to `date`. Add a separate, >> normative >> > > > > > > manifest-encoding clause so projection and >> expression-evaluation >> > > > > > > semantics that depend on the type model stay untouched. >> > > > > > > >> > > > > > > Reasoning: when Java, PyIceberg, and Rust all write logical >> `date`, >> > > > > > > that's the de facto wire format. Forcing them to switch to >> plain `int` >> > > > > > > to match a literal reading of the transform table would churn >> three >> > > > > > > implementations and leave every existing manifest >> "non-conforming" >> > > > > > > forever. Aligning Go with the dominant writer convention >> costs one >> > > > > > > implementation change (PR #915 already proposes it) and zero >> historical >> > > > > > > churn. >> > > > > > > >> > > > > > > The underlying ambiguity is that "result type" (logical >> Iceberg type) >> > > > > > > and "Avro manifest encoding" (wire format) were conflated. >> Separating >> > > > > > > them in spec text removes the ambiguity without changing the >> type >> > > > > > > system. >> > > > > > > >> > > > > > > Happy to drive the spec PR and then iceberg-go writer + reader >> > > > > > > alignment. >> > > > > > > >> > > > > > > Best, >> > > > > > > Andrei >> > > > > > > >> > > > > > > On Tue, May 19, 2026 at 5:45 PM Kevin Liu < >> [email protected]> >> > > > > wrote: >> > > > > > > >> > > > > > >> Hi all, >> > > > > > >> >> > > > > > >> I'd like to invite the community to discuss a spec ambiguity >> in Apache >> > > > > > >> Iceberg that has caused some confusion across >> implementations. We've >> > > > > seen >> > > > > > >> this come up in Python, Rust, and now Go. >> > > > > > >> >> > > > > > >> The issue: the spec documents the `day` partition >> transform's result >> > > > > type >> > > > > > >> as plain `int`, but Java, PyIceberg, and Rust all write >> manifest >> > > > > partition >> > > > > > >> fields using Avro's logical `date` type. Go currently writes >> plain >> > > > > `int`, >> > > > > > >> which is the strict reading of the spec. Since both forms >> have the >> > > > > same >> > > > > > >> physical representation, the difference is only the Avro >> schema >> > > > > annotation >> > > > > > >> -- but it's worth clarifying the spec so all implementations >> are >> > > > > aligned. >> > > > > > >> >> > > > > > >> The full analysis, including a breakdown of each >> implementation's >> > > > > > >> writer/reader behavior and proposed resolution options, is >> here: >> > > > > > >> https://github.com/apache/iceberg/issues/16414 >> > > > > > >> >> > > > > > >> At a high level, the questions for the community are: >> > > > > > >> 1. What should implementations write: Avro `int` (plain >> integer) or >> > > > > Avro >> > > > > > >> `date` (integer with a date logical type)? >> > > > > > >> 2. Should implementations be required to read both forms, or >> just >> > > > > > >> encouraged to? >> > > > > > >> 3. Should the spec's transform result type table be updated >> from >> > > > > `int` to >> > > > > > >> `date`? >> > > > > > >> >> > > > > > >> I'd love to hear your thoughts. Thanks! >> > > > > > >> >> > > > > > >> Best, >> > > > > > >> Kevin Liu >> > > > > > >> >> > > > > > > >> > > > > > >> > > > > >> > > > >> > >> >
