[feature request] return table operation summaries

[Anton-Tarazi]

Feature Request / Improvement

I think it would be valuable if Table operations like append or delete returned some summaries of the operation such as the number of data files edited, similar to how upsert returns an UpsertResult. Something I believe would be particularly useful is if delete/ override returned information about whether it was an efficient metadata-only delete or whether data files had to be rewritten.

For example delete could return something like:

@dataclass
class DeleteResult:
    files_removed: int = 0
    files_rewritten: int = 0
    rows_deleted: int = 0

I'd be happy to work on this but wanted to get the community's feedback given that this would be a (nonbreaking) public API change.

[Fokko]

Append and delete operations typically create one snapshot. The Snapshot has a Summary which typically (could differ per engine) contain summaries: https://iceberg.apache.org/spec/#metrics

[jayceslesar]

Maybe upsert is the odd one out here and it should be making use of the snapshot metrics rather than keeping track of the metrics itself?

[Anton-Tarazi]

@Fokko thank you, summary was exactly what I had in mind. I agree with @jayceslesar that it does appear to be inconsistent when upsert returns metrics but the other table operations do not.