I'm just pretty neutral here with a slight bias towards Parquet only. I don't think supporting Avro is much more difficult, but that's mostly my prejudice from the Java library. It's probably better for us to converge on a single file format if possible so I think Parquet only is a good step in that direction.
On Tue, Aug 11, 2026 at 1:42 PM Anoop Johnson <[email protected]> wrote: > It would be great to make V4 manifest Parquet-only. This simplifies the > spec and the implementation complexity and should improve read performance > as Steven noted. Also we don't currently keep track of the root manifest > format currently. So if we really want to support Avro root manifests, we > need to start tracking the format. The alternative is to require writers to > always produce the root manifest in Parquet. But then there is no point in > supporting Avro leaf manifests if writers are required to produce root in > Parquet anyway. > > Note that for v4 table upgrades we will support v3 leaf manifests which > are in Avro - so the Parquet restriction applies to new V4 manifests only. > > Best, > Anoop > > On Tue, Aug 11, 2026 at 11:29 AM Steven Wu <[email protected]> wrote: > >> Hi, >> >> During today’s column update sync, we discussed whether to keep the Avro >> format option for V4 manifest files. The initial inclination was to keep it >> because it already exists, even though Avro won’t support projection reads >> on manifest files (including column stats). >> >> With both Avro and Parquet available, integrations and engines would need >> to choose. We expect most will pick Parquet for projection-read support. >> That raises a question: should we instead require Parquet for V4 manifests >> to reduce the cognitive and decision burden on integrations? >> >> This also aligns with Iceberg’s usual priority of read >> performance—especially query scan planning, where projecting column stats >> from manifests matters. >> >> In the sync, most people generally agreed with making V4 manifests >> *Parquet-only*. I’m sending this to collect any feedback or concerns >> from the broader community before we settle on that direction. >> Thanks, >> Steven >> >> P.S. I uploaded the recording to the YouTube channel here >> <https://youtu.be/dDZKzz3PKIk?t=2925> (relevant discussion started at >> 48:45). >> >
