Support projection in arrow::io::ipc:read::FileReader:new

[ghuls]

Describe your feature request

Support projection (reading only specific columns) when reading an IPC file in lazy mode:

https://github.com/pola-rs/polars/blob/1a6db2919ef312e3da959c5f74da09e6cd99ebb0/polars/polars-io/src/ipc.rs

Support for projection in lazy mode can be adapted from:
https://github.com/pola-rs/polars/blob/master/polars/polars-io/src/parquet.rs

Specifying column names to load from IPC and parquet in eager mode, would be great too:

polars/polars/polars-io/src/ipc.rs

Line 96 in 1a6db29

let ipc_reader = read::FileReader::new(&mut self.reader, metadata, None);

https://github.com/pola-rs/polars/blob/master/polars/polars-io/src/parquet.rs#L111-L117

[illumination-k]

May I work on this issue?

[ghuls]

@illumination-k I think @ritchie46 is working on pl.scan_ipc(Support projection (reading only specific columns) when reading an IPC file in lazy mode:) already. Or I misunderstood and he was planning to work on it.

If you could tackle reading specified columns in eager mode, that would be great.

[illumination-k]

@ghuls Thanks for your reply. Let me check. The tasks are implementing with_columns, with_projection in earger mode and rewriting finish method, right? If so, I would like to tackle this.