Reuse Rows allocation in SortPreservingMergeStream / `RowCursorStream`

[Dandandan]

Is your feature request related to a problem or challenge?

While reviewing our Sort code, I found Rows is being allocated within RowCursorStream for each batch (via RowConverter::convert_columns)
This involves a number allocations (exponentially allocating based on Vec) for each batch.
We should avoid this and reuse Rows for the stream.

Describe the solution you'd like

Find a way to reuse Rows for the entire stream.

Describe alternatives you've considered

No response

Additional context

No response

[Dandandan]

FYI: It probably involves some hackery or redesign as a RowValues currently takes an owned Rows.

[Dandandan]

Interesting @acking-you, do you have some code/branch you could share?

I wonder if you tried out using RowConverter::append (e.g. clear + append)
https://docs.rs/arrow-row/latest/arrow_row/struct.RowConverter.html#method.append rather than convert_columns? This approach is used in other areas to reduce allocations.