Hi Andrei, Thanks for bringing this back to the dev list and the detailed writeup. I understand the motivating case is catalog-to-catalog / federation.
My concerns are mostly when labels are used for governance. I have raised these in the spec PR already linking them as well : - Attachment / inheritance semantics: https://github.com/apache/iceberg/pull/15750#discussion_r3647710626 - Nested-field label conflicts: https://github.com/apache/iceberg/pull/15750#discussion_r3648060761 - Stable id for cross-catalog sync: https://github.com/apache/iceberg/pull/15750#discussion_r3648112804 In a nutshell, these boil down to: 1. Why do we even need labels when *config* exists then ? *LoadTableResult#config* is already a string map that catalogs ship non-standard keys through. The use cases listed - ownership and point of contact, cost attribution, retention / TTL / GDPR cleanup, discovery - can all be carried there today. 2. Why not do the structured entity first? "Flat now, structured later" why not do structured entities first then ? Federation / Catalog Sync is where I expect it to matter most: I cannot tell inherited from direct, and a renamed label leaves me nothing stable to bind policy to. I could be convinced otherwise, but I would rather we work these out here than defer them to the structured follow-up, since the read path is what implementers will build against. Looking forward to hearing from other community members as well on their take on this scenario. Thanks, Prashant On Wed, Aug 26, 2026 at 2:04 PM Andrei Tserakhau via dev < [email protected]> wrote: > Hi all! > > Coming back from vacation, I want to re-iterate and close the loop over the > catalog community sync [1], where Labels in IRC [2] were the main topic of > discussion. > > Thanks to everyone who joined and participated, this was a good discussion. > > I want to bring focus back to the proposal and SPEC change [3] that's > actually on the table: a single optional `labels` field on the load > response, flat k/v the catalog already owns, read-only, backward > compatible, > with no interpretation or enforcement defined by the spec. > > This is a deliberate choice to keep it minimal. Iceberg always leans toward > standardizing the least common thing to enable value, while keeping the > rest > as innovation space for others (in this case, catalogs). > > This proposal leans into openness and exposes catalog metadata that drives > many capabilities like policy enforcement, lifecycle management, data > governance, attribution, etc. The mechanics of these capabilities are well > outside of Iceberg's main function, but critical for systems managing > Iceberg data. > > There's a lot of confusion between implementations and what the spec > enables, but where the room converged was: > > - Labels are catalog-owned metadata exposed at load time. The catalog > presents what it knows about an object when the object is loaded, nothing > more. Labels are similar to table properties, but expose data owned by > the > catalog rather than by table metadata. > > - It is not a coordination protocol. Renames / x-system sync / identity and > lineage / semantics of a label across catalogs are questions that live > outside this protocol. The protocol's goal is only to present the current > view at the current moment in time. > > - Labels are not competing with Read Restrictions, they are complementary > tools. Read Restrictions is server-side enforcement (the catalog > evaluates > policy), while Labels are client-side (the catalog exposes context, but > consumers/engines decide what to do with it). Read Restrictions are > especially good when you are fully a client of another catalog, while > Labels can be useful when you consume another catalog and apply your own > policies without a trust relationship. We need both of these approaches > in > IRC. > > - Governance is one use case, not the whole point. Most of the discussion > was centered around ABAC/TBAC, but the value is broader: ownership and > point of contact, cost attribution, retention / TTL / GDPR cleanup, > attribute-based maintenance, discovery and AI context. None of these need > enforcement, identity, or a tag-entity model to be useful. > > - The structured entity for tags (stable identity, rename semantics, > inheritance, x-catalog lineage) is an important follow-up, but the goal > here is to unblock value while we discuss the full entity model. This is > a > similar pattern to what we already have in IRC: a dedicated entity API is > richer than exposure through another API. I will keep driving the > structured tag entity further. > > I would like to move to a VOTE on the read path. > > If there are concrete concerns about the spec as proposed, the field, the > shape, or compatibility, let's discuss them in this thread. > > Use-case-specific coordination (x-system tag sync, rename semantics, > identity binding) are the main topics for the structured follow-up and, per > the discussion, are out of scope for the read path. > > [1] Catalog Sync Recording: https://www.youtube.com/watch?v=lCTV-Rhiwyc > [2] Spec Proposal doc: > https://docs.google.com/document/d/1aj-6JlfBiMYEEVtNuh5WLMOrRQiMCcyYUGbouPM4hXI/edit?tab=t.0#heading=h.2w0kmp1v1gwv > [3] Spec PR: https://github.com/apache/iceberg/pull/15750 > > Best, > Andrei >
