Hi, Jason. Thanks for bringing this up. When integrating Apache Iceberg with Apache Flink (incubating)[1], we also needed to capture commit results and store snapshot IDs in our internal state to track tiering progress. However, we can’t simply refresh the table to get the latest snapshot, since other writers may be concurrently committing to the same table — and we only want the snapshot generated by our own commit. To work around this, we used the Iceberg listener mechanism[2], but this still feels a bit like a hack. It would be much cleaner if Iceberg provided a standard interface to return commit results.
[1] https://github.com/apache/fluss [2] https://github.com/apache/fluss/blob/03313a9b02dca57c87c406f0ecf396b08fa8726a/fluss-lake/fluss-lake-iceberg/src/main/java/org/apache/fluss/lake/iceberg/tiering/IcebergLakeCommitter.java#L328 Best regards, Yuxia 发件人: "Russell Spitzer" <russell.spit...@gmail.com> 收件人: "dev" <dev@iceberg.apache.org> 发送时间: 星期五, 2025年 9 月 12日 上午 2:21:56 主题: Re: [DISCUSS] Proposal: Returning Commit Results from commit() I don't think I'm opposed to this idea in general but I think we probably need to get some concrete examples of how this is going to be used by a consumer. Since this would require modifying every implementation of XXXOperation that we currently have; it's a rather heavy change and should probably be backed by some concrete use cases where the client needs the exact metadata object produced by the operation. We also need to actually nail down in the proposal the return type as you mentioned. I don't think there is a problem returning a table metadata object but this would be rather complicated for any REST catalog interface. A Rest Catalog would still require a round trip to the Catalog to get the new state since there is no other way to know what was actually committed as the metadata.json is written remotely so we would still be leaning on TableOperations to actually figure out what that is. For the future, we probably will also have issues as we move towards a "send changes" to the catalog model instead of a "send new state" model. In those cases we will also have the issue of not actually knowing what was committed without contacting the catalog after the commit succeeds. So we also need to consider how the REST Spec would need to change to support this. On Thu, Sep 11, 2025 at 5:08 AM Jason Fine <jason.f...@qlik.com.invalid> wrote: Hi all, I’d like to start a discussion about [ https://github.com/apache/iceberg/pull/13987 | PR #13987 ] which adds support for returning results from the commit() operation. What this PR is about The core idea is: when a client calls commit() , they should be able to immediately obtain the updated information produced by the commit (whether that’s a new snapshot or updated table metadata), instead of performing a redundant refresh() afterwards. This is useful for distributed system that want to track their progress and save progress state. But I’m sure it will have many other uses as well. Calling refresh unnecessarily is a slowdown, but also it also counts against your quota for rate limits in certain services. I know some implementations currently don’t call refresh() but others do, and the interface doesn’t enforce this, and the wanted information is already available in the client after the commit as it produced it. Key points/concerns raised * API compatibility breakage : Several folks pointed out that returning updated snapshot or metadata from commit() changes the existing API contract . We can resolve this by adding a new method instead. * What counts as a snapshot : Some committed operations don’t produce snapshots — e.g. metadata operations (schema changes, property updates). The distinction between operations that produce snapshots vs ones that just update metadata matters . Perhaps returning the TableMetadata like mentioned below always is a good a solution. * Behavior varies by catalog implementation : Some implementations already refresh automatically ( shouldRefresh etc.), others don’t. RestCatalog vs Metastore vs others behave differently. Proposal / Possible compromises >From the discussion, here are options that seem promising to me, or ways to >mitigate the drawbacks: 1. Add a new method, e.g. commitWithResult(...) This method would commit and return the updated snapshot / metadata, but leave the existing commit() method with its current behavior. That way we retain backward compatibility. 2. Return a read-only metadata snapshot If returning the full metadata object is too heavy or too risky, return a minimal “read ‐ only” summary containing just what is needed (snapshotId, maybe timestamp). This reduces implementation risk. [ https://github.com/apache/iceberg/pull/14023/files#diff-c941602822c0e1c24d7de4ef5db76105d414d7b3f0b26df7ca75e76ba79e9663 | GitHub ] . This is also helpful if we want to avoid adding a new Generic argument to the SnpashotUpdate interface. Please let me know what you think about this suggestion and how we can move it forwards. 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