docs/source/contributor-guide/roadmap.md

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# Comet Roadmap

Comet is an open-source project and contributors are welcome to work on any issues at any time, but we find it
helpful to have a roadmap for some of the major items that require coordination between contributors.

## Major Initiatives

### Iceberg Integration

Iceberg integration is still a work-in-progress ([#2060]), with major improvements expected in the next few
releases. The default `auto` scan mode now uses `native_iceberg_compat` instead of `native_comet`, enabling
support for complex types.

[#2060]: https://github.com/apache/datafusion-comet/issues/2060

### Spark 4.0 Support

Comet has experimental support for Spark 4.0, but there is more work to do ([#1637]), such as enabling
more Spark SQL tests and fully implementing ANSI support ([#313]) for all supported expressions.

[#313]: https://github.com/apache/datafusion-comet/issues/313
[#1637]: https://github.com/apache/datafusion-comet/issues/1637

### Removing the native_comet scan implementation

The `native_comet` scan implementation is now deprecated and will be removed in a future release ([#2186], [#2177]).
This is the original scan implementation that uses mutable buffers (which is incompatible with best practices around
Arrow FFI) and does not support complex types.

Now that the default `auto` scan mode uses `native_iceberg_compat` (which is based on DataFusion's `DataSourceExec`),
we can proceed with removing the `native_comet` scan implementation, and then improve the efficiency of our use of
Arrow FFI ([#2171]).

[#2186]: https://github.com/apache/datafusion-comet/issues/2186
[#2171]: https://github.com/apache/datafusion-comet/issues/2171
[#2177]: https://github.com/apache/datafusion-comet/issues/2177

## Ongoing Improvements

In addition to the major initiatives above, we have the following ongoing areas of work:

- Adding support for more Spark expressions
- Moving more expressions to the `datafusion-spark` crate in the core DataFusion repository
- Performance tuning
- Nested type support improvements