Micah, many people will be OOO in the next two weeks. Can we extend the feedback deadline to at least 1-2 weeks after the new year?
On Fri, Dec 19, 2025 at 8:45 AM Micah Kornfield <[email protected]> wrote: > > I have no problem with adding this discussion to the single file work, > but I'm not sure that would speed it up? Seems like this is a pretty > independent addition to the metadata layout? > > Yes, it is fairly independent. The main reason I wanted to consolidate in > the doc, it appears there is a bit of metadata re-arrangement and new > fields. I wanted to make sure that: > > 1. We avoid field ID conflicts. > 2. When writing up the final spec changes it is easy to manage and not > create a dependency one way or another between the two of these. > > Happy to keep the implementation of the guard-rails as a separate piece of > work. > > Cheers, > Micah > > On Fri, Dec 19, 2025 at 7:31 AM Russell Spitzer <[email protected]> > wrote: > >> I have no problem with adding this discussion to the single file work, >> but I'm not sure that would speed it up? Seems like this is a pretty >> independent addition to the metadata layout? >> >> On Thu, Dec 18, 2025 at 6:28 PM Micah Kornfield <[email protected]> >> wrote: >> >>> Thanks for the clarification, Micah! I want to explicitly call out (and >>>> double-confirm) the key principle here: all tags must be strictly optional >>>> and never required for correctness or basic functionality. Engines should >>>> always be able to safely drop or ignore tags without breaking reads or >>>> writes, with the only possible impact being suboptimal behavior (e.g., >>>> extra I/O), as you described. >>> >>> >>> 100% I will also add this summary to the bottom of the requirements >>> section. >>> >>> Based on mailing list discussion and doc comments (or lack thereof), it >>> does not seem like there are strong objections to adding this for V4. >>> Prashant seemed to maybe have concerns, so I'd like to understand if they >>> are blockers. >>> >>> If there isn't additional feedback by the end of next week, I'd like to >>> assume a lazy consensus and consolidate this with the single file >>> improvement work, which has already reorganized the metadata schema [1]. >>> Please let me know if there is a different process. >>> >>> Thanks, >>> Micah >>> >>> [1] >>> https://docs.google.com/document/d/1k4x8utgh41Sn1tr98eynDKCWq035SV_f75rtNHcerVw/edit?tab=t.0#heading=h.unn922df0zzw >>> >>> On Wed, Dec 17, 2025 at 5:38 PM Yufei Gu <[email protected]> wrote: >>> >>>> Thanks for the clarification, Micah! I want to explicitly call out (and >>>> double-confirm) the key principle here: all tags must be strictly optional >>>> and never required for correctness or basic functionality. Engines should >>>> always be able to safely drop or ignore tags without breaking reads or >>>> writes, with the only possible impact being suboptimal behavior (e.g., >>>> extra I/O), as you described. >>>> >>>> As long as this constraint is clearly stated and enforced, the >>>> trade-off feels reasonable to me. >>>> >>>> Yufei >>>> >>>> >>>> On Mon, Dec 15, 2025 at 4:28 PM Micah Kornfield <[email protected]> >>>> wrote: >>>> >>>>> Hi Yufei, >>>>> >>>>>> If one engine started to rely on a tag for certain reasons(like >>>>>> clustering algorithm), would data file rewrite(compaction) by another >>>>>> engine remove the tag, and break the engine relying on it. >>>>> >>>>> >>>>> The intent here is that dropping tags should never break an engine. >>>>> But it could cause suboptimal operations. For instance, one example I >>>>> brought in the docs is using tags to cache parquet footer size, to make >>>>> sure it is fetched in 1 I/O. >>>>> >>>>> In this case the following would occur. >>>>> >>>>> 1. Engine 1 does a write to file 1 and records its footer size in >>>>> tags. >>>>> 2. Engine 2 does a rewrite/compactions and produces File 2 without >>>>> tags. >>>>> 3. Engine 1 then tries to read file 2. The tag for footer length is >>>>> missing so it falls back reading a reasonable number of bytes from the end >>>>> of the parquet file, hoping the entire footer is retrieved (and if it >>>>> isn't >>>>> a second I/O is necessary). >>>>> >>>>> Similarly for clustering algorithms, I think the result could yield a >>>>> sub-optimally clustered table, or perhaps redundant clustering operations >>>>> but shouldn't break anything. This is no worse then the case today though >>>>> if engine 1 and engine 2 have different clustering algorithms and they are >>>>> being run in interleaved fashion on the same table. In this case it is >>>>> highly likely that some amount of duplicate compaction is happening. >>>>> >>>>> In the current proposal, any metadata that is required for proper >>>>> functioning should never be put in tags. >>>>> >>>>> Thanks, >>>>> Micah >>>>> >>>>> >>>>> On Mon, Dec 15, 2025 at 4:02 PM Yufei Gu <[email protected]> wrote: >>>>> >>>>>> Thanks for the proposal! >>>>>> >>>>>> If one engine started to rely on a tag for certain reasons(like >>>>>> clustering algorithm), would data file rewrite(compaction) by another >>>>>> engine remove the tag, and break the engine relying on it. >>>>>> >>>>>> Yufei >>>>>> >>>>>> >>>>>> On Wed, Dec 10, 2025 at 2:58 PM Micah Kornfield < >>>>>> [email protected]> wrote: >>>>>> >>>>>>> Hi Iceberg Dev, >>>>>>> I added a proposal [1] to add a key-value tags field for files in V4 >>>>>>> metadata [2]. More details are in the document but the intent is to >>>>>>> allow >>>>>>> engines to store optional metadata associated with these files: >>>>>>> >>>>>>> 1. The proposed field is optional and cannot be used for metadata >>>>>>> required for reading the table correctly. >>>>>>> 2. It also proposes guard-rails for not letting tags cause metadata >>>>>>> bloat. >>>>>>> >>>>>>> Looking forward to hearing everyone's thoughts and feedback. >>>>>>> >>>>>>> Thanks, >>>>>>> Micah >>>>>>> >>>>>>> [1] https://github.com/apache/iceberg/issues/14815 >>>>>>> [2] >>>>>>> https://docs.google.com/document/d/16flxDXjpBiAs_cF3sjCsa7GlvSHQ0Mmm74c8yvYQlSA/edit?tab=t.0#heading=h.cnpb2lth3egz >>>>>>> >>>>>>>
