docs: Add Roadmap (#2191)

* Roadmap

* Update docs/source/contributor-guide/roadmap.md

Co-authored-by: Oleks V <[email protected]>

---------

Co-authored-by: Oleks V <[email protected]>

Author: andygrove

docs/source/contributor-guide/contributing.md

@@ -30,7 +30,7 @@ Here are some areas where you can help:
 
 ## Finding issues to work on
 
-We maintain a list of good first issues in GitHub [here](https://github.com/apache/datafusion-comet/issues?q=is%3Aopen+is%3Aissue+label%3A%22good+first+issue%22).
+We maintain a list of good first issues in GitHub [here](https://github.com/apache/datafusion-comet/issues?q=is%3Aopen+is%3Aissue+label%3A%22good+first+issue%22). We also have a [roadmap](roadmap.md).
 
 ## Reporting issues
 

docs/source/contributor-guide/roadmap.md

@@ -0,0 +1,65 @@
+<!--
+Licensed to the Apache Software Foundation (ASF) under one
+or more contributor license agreements.  See the NOTICE file
+distributed with this work for additional information
+regarding copyright ownership.  The ASF licenses this file
+to you under the Apache License, Version 2.0 (the
+"License"); you may not use this file except in compliance
+with the License.  You may obtain a copy of the License at
+
+  http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing,
+software distributed under the License is distributed on an
+"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+KIND, either express or implied.  See the License for the
+specific language governing permissions and limitations
+under the License.
+-->
+
+# 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. Once this integration is complete, we plan on switching from the `native_comet` scan to the 
+`native_iceberg_compat` scan ([#2189]) so that complex types can be supported.
+
+[#2060]: https://github.com/apache/datafusion-comet/issues/2060
+[#2189]: https://github.com/apache/datafusion-comet/issues/2189
+
+### Spark 4.0.0 Support
+
+Comet has experimental support for Spark 4.0.0, 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
+
+We are working towards deprecating ([#2186]) and removing ([#2177]) the `native_comet` scan implementation, which
+is the originally scan implementation that uses mutable buffers (which is incompatible with best practices around
+Arrow FFI) and does not support complex types.
+
+Once we are using the `native_iceberg_compat` scan (which is based on DataFusion's `DataSourceExec`) in the Iceberg 
+integration, we will be able to remove the `native_comet` scan implementation, and can 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

docs/source/index.rst

@@ -68,6 +68,7 @@ as a native runtime to achieve improvement in terms of query efficiency and quer
    Tracing <contributor-guide/tracing>
    Profiling Native Code <contributor-guide/profiling_native_code>
    Spark SQL Tests <contributor-guide/spark-sql-tests.md>
+   Roadmap <contributor-guide/roadmap.md>
    Github and Issue Tracker <https://github.com/apache/datafusion-comet>
 
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