add into_inner method to ArrowWriter

[jiacai2050]

Is your feature request related to a problem or challenge? Please describe what you are trying to do.

For now, there is no way to retrieve Writer passed into ArrowWriter back, this means that we have to use Arc(or something similar) to wrap Writer in order to get ownership.

Describe the solution you'd like

Add into_inner method to ArrowWriter, just like parquet2

• https://docs.rs/parquet2/0.15.1/parquet2/write/struct.FileWriter.html#method.into_inner

Describe alternatives you've considered

Additional context

[tustvold]

Have you tried passing &mut W to the writer instead?

See the example here - https://docs.rs/parquet/latest/parquet/arrow/arrow_writer/struct.ArrowWriter.html

TBC I think we should add this API, just trying to unblock you 😅

[jiacai2050]

&mut W is one solution, but not works for my case, I need ownership(or static lifetime) since if it's behind a trait object.

Will submit a PR later.

[tustvold]

I need ownership(or static lifetime) since if it's behind a trait object.

FWIW trait objects need not have static lifetimes, but I concede your point that there are situations where a static lifetime is necessary to avoid self-referential structures.