Sounds good, will wait until next year. On Fri, Dec 19, 2025 at 2:13 PM Steven Wu <[email protected]> wrote:
> 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 >>>>>>>> >>>>>>>>
