I would agree the best path forward is to note the current behavior for v1/v2 since that's well established and address the behavior in v3.
For compatibility with existing libraries, we should maintain that `-1` is equivalent to no snapshot and it should be written for v1/v2. With V3 we should support `-1` for backwards compatibility (though there's low likelihood that someone will promote an empty table), but always write `null`. I believe this is in part due to TableMetadata tracking the current-snapshot-id as a `long` value (as opposed to a Long) reference, which resulted in this oversight. -Dan On Tue, Feb 18, 2025 at 11:57 AM rdb...@gmail.com <rdb...@gmail.com> wrote: > +1 to reverting PT 11560 in main and 1.8.1. That avoids unnecessary > incompatibility with older readers. > > I also agree that we should update the spec to say what Russell suggests: > > that -1 has meant "no current snapshot" in the past and is equivalent to > missing/null. > > That's a correct description of the behavior. > > I don't think that we should create new requirements for this that didn't > previously exist -- that is, I don't see much value in going back to > mandate this behavior when writing v1 or v2 tables. If an implementation > were writing null for the current snapshot ID up until now, I don't think > that we can say that behavior was or is incorrect. It was an > incompatibility with the Java implementation and we should note the > behavior in the "Implementation Notes" section. > > > How about reverting #11560 for 1.8.1, and then reinstating this for > 2.0.0? > > I think we need to fix this at a format version boundary, not a library > version boundary. I'd be up for reinstating the write change for v3. > > On Tue, Feb 18, 2025 at 7:56 AM Russell Spitzer <russell.spit...@gmail.com> > wrote: > >> The only thing I think I agree with is defining that -1 has meant "no >> current snapshot" in the past and >> is equivalent to a missing/nuil (if we have to specify that) . >> >> I don't think there is any reason to change the behavior of writing null >> / missing unless >> that's really a point of confusion for folks. Is there a JSON library >> folks are using >> which distinguishes between missing/null? >> >> Would having field:null be the same as missing have avoided the issue >> because it seems like libraries >> that only handled non-null would also not handle "missing" >> current-snapshot-id as well? >> >> I'd really like to hear from other implementers here since changing all >> this again would be a lot of >> work and I thought we had understanding of Optional == Nullable as a >> valid thing in the spec. >> >> On Tue, Feb 18, 2025 at 7:35 AM Robert Stupp <sn...@snazy.de> wrote: >> >>> Correcting myself: schema/spec/sort seem to be always present - please >>> ignore that part in my previous email. The valid values for those fields >>> however should be defined. >>> On 18.02.25 14:29, Robert Stupp wrote: >>> >>> Reality is that Iceberg did write '-1' into current-snapshot-id (and >>> other "non-exist" marker values for schema/spec/sort) instead of omitting >>> the field. >>> >>> Side note: the table-spec says that these fields are optional, but >>> nothing about whether it is nullable. >>> >>> The spec should at least be amended to explicitly define the valid >>> values (-1 for current-snapshot-id for no snapshot is just a fact now that >>> it's there). IMO that field being 'null' isn't defined in the spec, but the >>> absence of the field is. >>> >>> Proposal for the implementation: >>> >>> * revert https://github.com/apache/iceberg/pull/11560 in 1.8.1 and on >>> main >>> >>> Proposal for the spec (for current-snapshot-id): >>> >>> * Define the valid value ranges for the field >>> * Define that the absence of the field means "no current snapshot" >>> * Define that the value -1 of the field means "no current snapshot" >>> * Define that the value 'null' of the field means "no current snapshot" >>> * Define that new implementations must not write the field if there's no >>> current snapshot >>> Proposal for the spec (for schema/spec/sort): >>> >>> * Define the valid value ranges for the fields >>> * Define the "schema/spec/sort not present" values (the fields are >>> optional for v1 but required for v2+v3). >>> * OR Define that "schema/spec/sort must be absent" if there is no >>> current schema/spec/sort. >>> >>> WDYT? >>> >>> On 17.02.25 21:07, Russell Spitzer wrote: >>> >>> It sounds like the argument here is that we should change the Spec for >>> V1, V2, and V3 to mark current-snapshot-id >>> as required. Then we should change all other implementations to follow >>> this new standard. I'm not sure that >>> is a good solution going forwards but I'm not sure of how we can support >>> catalogs/engines that cannot handle a null >>> correctly in this situation otherwise. Perhaps we should source out to >>> see if any other implementers worked off the >>> assumption of a non-optional "current-snapshot-id" and if we get a >>> critical mass we can try to make that change? >>> Because of how wide that change would be, I think we would need pretty >>> broad consensus to do so. >>> >>> We could possibly also have a flag to allow the old behavior but that >>> also feels wrong to me, we have often gone with a motto of >>> read "wrong" write "correct" for things like this in the past and >>> continuing to write "wrong" is a disservice to any >>> new implementers . When we do have a contradiction between our >>> implementation and the spec I think we have >>> to trust that implementers followed the spec and fix the core library. >>> >>> Are there any other solutions here? >>> >>> On Mon, Feb 17, 2025 at 11:45 AM Fokko Driesprong <fo...@apache.org> >>> wrote: >>> >>>> Hey Robert, >>>> >>>> The thing is, that -1 cannot "go away". >>>> >>>> >>>> Yes, I agree, but that's also the case for null, as the field is optional >>>> in the spec >>>> <https://iceberg.apache.org/spec/?column-projection#table-metadata-fields>. >>>> Therefore we support both in PyIceberg >>>> <https://github.com/apache/iceberg-python/blob/300b8405a0fe7d0111321e5644d704026af9266b/pyiceberg/table/metadata.py#L71-L77>, >>>> Iceberg-Rust >>>> <https://github.com/apache/iceberg-rust/blob/752d69041e0461989c48dd1ca79bcff577776f5d/crates/iceberg/src/spec/table_metadata.rs#L500>, >>>> Iceberg-Java >>>> <https://github.com/apache/iceberg/blob/bcbbd0344623ffea5b092e2de5debb0bc12892a1/core/src/main/java/org/apache/iceberg/TableMetadataParser.java#L458-L462>, >>>> and Iceberg-Go >>>> <https://github.com/apache/iceberg-go/blob/ada5480954d9b41d2f8eb4c765523614fad65e1a/table/metadata.go#L837-L841>. >>>> On the write side, they all produce null instead of -1. Therefore, I >>>> was surprised that it comes up now, and not earlier. >>>> >>>> I'd prefer to keep the previous behavior - otherwise implementations >>>>> may fall back to 0, which is definitely wrong. >>>> >>>> >>>> I'm not seeing why it would fall back to 0, and I agree, that's wrong. >>>> >>>> Would be better IMHO not to break existing implementations / render >>>>> existing setups incompatible with Iceberg 1.8. >>>> >>>> >>>> In my opinion, if this had been caught in an RC, it would be open for >>>> discussion, but that ship has sailed. Let's hear what others think. >>>> >>>> Kind regards, >>>> Fokko >>>> >>>> Op ma 17 feb 2025 om 18:16 schreef Robert Stupp <sn...@snazy.de>: >>>> >>>>> Hi Fokko, >>>>> >>>>> sure, in general "absent" or "null" would be cleaner. But now we have >>>>> two representations for the same case - I suspect most went with the >>>>> "reference behavior". >>>>> >>>>> The thing is, that -1 cannot "go away". >>>>> >>>>> I'd prefer to keep the previous behavior - otherwise implementations >>>>> may fall back to 0, which is definitely wrong. Would be better IMHO not to >>>>> break existing implementations / render existing setups incompatible with >>>>> Iceberg 1.8. >>>>> >>>>> >>>>> On 17.02.25 15:49, Fokko Driesprong wrote: >>>>> >>>>> Hey Robert, >>>>> >>>>> Thanks for raising this. >>>>> >>>>> snapshot-ID -1 isn't per-se invalid, because the valid values are not >>>>>> defined in the spec. >>>>> >>>>> >>>>> For me, this is invalid, since there is no snapshot with -1 in the >>>>> snapshots property. In the tests with the PR, you can see that there >>>>> are no snapshots >>>>> <https://github.com/apache/iceberg/pull/11560/files#diff-41bdfb6698d2aa7b47ff7d5fabc558a5a64f8b7496fe1bcd8f8ecb69b2afc128R112>. >>>>> A year ago we had a similar discussion on PyIceberg >>>>> <https://py.iceberg.apache.org/configuration/#backward-compatibility> >>>>> around this and this ended up in adding a flag to fall back to the old >>>>> behavior. I do agree that we should have communicated this more clearly >>>>> with the release. >>>>> >>>>> Kind regards, >>>>> Fokko >>>>> >>>>> >>>>> >>>>> >>>>> Op ma 17 feb 2025 om 12:25 schreef Robert Stupp <sn...@snazy.de>: >>>>> >>>>>> Feels like https://github.com/apache/iceberg/pull/11560 introduced a >>>>>> behavior change. >>>>>> >>>>>> snapshot-ID -1 isn't per-se invalid, because the valid values are not >>>>>> defined in the spec. >>>>>> >>>>>> Previous Iceberg-Java versions always produced -1 if there's no >>>>>> current snapshot - 1.8 produces `null` in that case. So there are now two >>>>>> _different_ values for "no current snapshot". >>>>>> >>>>>> Implementations that rely on the behavior of the "reference >>>>>> implementation" (Iceberg-Java) do now fail in case there's no current >>>>>> snapshot. >>>>>> On 13.02.25 10:09, Amogh Jahagirdar wrote: >>>>>> >>>>>> I'm pleased to announce the release of Apache Iceberg 1.8.0! >>>>>> >>>>>> Apache Iceberg is an open table format for huge analytic datasets. >>>>>> Iceberg >>>>>> delivers high query performance for tables with tens of petabytes of >>>>>> data, >>>>>> along with atomic commits, concurrent writes, and SQL-compatible table >>>>>> evolution. >>>>>> >>>>>> This release can be downloaded from: >>>>>> https://www.apache.org/dyn/closer.cgi/iceberg/apache-iceberg-1.8.0/apache-iceberg-1.8.0.tar.gz >>>>>> >>>>>> >>>>>> Release notes: https://iceberg.apache.org/releases/#180-release >>>>>> <https://iceberg.apache.org/releases/180-release> >>>>>> >>>>>> Java artifacts are available from Maven Central. >>>>>> >>>>>> Thanks to everyone for contributing! >>>>>> >>>>>> -- >>>>>> Robert Stupp >>>>>> @snazy >>>>>> >>>>>> -- >>>>> Robert Stupp >>>>> @snazy >>>>> >>>>> -- >>> Robert Stupp >>> @snazy >>> >>> -- >>> Robert Stupp >>> @snazy >>> >>>
