[Feature Request] Enable converting from Iceberg to Delta

[scottsand-db]

Feature request

Overview

Enable converting parquet-backed Iceberg tables to Delta tables without rewriting parquet files. This new Delta Table will need to be at least protocol version { reader=2, writer=5 } as Column Mapping will be needed during the conversion.

Motivation

We want to make it easier for users to convert their existing Iceberg tables to Delta tables and start experiencing all the wonderful benefits of Delta! Having a native Iceberg converter that doesn't rewrite parquet files should help smoothen this transition.

Further details

We will have to think about what this API / module / JAR / artifact, etc. will look like. Would love to hear feedback and thoughts from the community!

[felipepessoto]

#1463 (comment) mention a couple of limitations. Is it the plan to address them before next release?

Are there any limitations on what types/features in Iceberg supported and not supported?

There are a few remaining things we don't yet support:

1. Converting hive based iceberg table
2. Converting non-parquet iceberg table
3. Converting special partition transformation rules (ref)
4. Converting iceberg with custom name mapping (ref)
5. Converting iceberg table with case-sensitive column names (ref)

Thanks

[tdas]

Each of these cases of iceberg tables are pretty complex to translate to Delta protocol. So it's tricky to get it done before the next release. We definitely welcome the community to help out.

[allisonport-db]

Closed by #1463