[parquet] Add row group index virtual column

[friendlymatthew]

Which issue does this PR close?

• Closes [Parquet] Support returning RowGroupIndex as a column #8641
• Related [Parquet] Virtual Column Support #8799

Rationale for this change

This PR adds support for storing row group indices as a virtual column, allowing users to determine which row group each row originated from

The usage pattern is quite simple, something like:

use parquet::arrow::RowGroupIndex;

let row_group_index_field = Arc::new(
    Field::new("row_group_index", DataType::Int64, false)
        .with_extension_type(RowGroupIndex)
);

let options = ArrowReaderOptions::new()
    .with_virtual_columns(vec![row_group_index_field])?;

let reader = ParquetRecordBatchReaderBuilder::try_new_with_options(file, options)?
    .build()?;

[friendlymatthew]

@Jefffrey if you have some bandwidth, I'd be curious to get your thoughts

[friendlymatthew]

cc @alamb

[Jefffrey]

@Jefffrey if you have some bandwidth, I'd be curious to get your thoughts

I'll see if I can take a look at this PR soon, though I will say it's been a while since I looked at the parquet codebase 😅

[adriangb]

This would be sweet! I like the idea of using an extension type as a marker, and letting the caller customize the column name.

[alamb]

I think the extension type marker was pioneered by @jkylling and @vustef

I will also try and review this sooner rather than later

[scovich]

Nice! (a few nits)

[scovich]

nit: I would expect m < n, so this is O(n) where n is the total row groups, and the loop below is O(m) where m is the number of selected row groups?

[scovich]

nit: I know this is how the row index reader did it, but since that code merged I learned that Iterator::by_ref is a thing.

Suggested change

	.extend((&mut self.remaining_indices).take(batch_size));
	.extend(self.remaining_indices.by_ref().take(batch_size));

It's not shorter, but does seem more readable?

(more below)

[scovich]

nit: is a match simpler?

Suggested change

	if metadata.is_some_and(str::is_empty) {
	Ok("")
	} else {
	Err(ArrowError::InvalidArgumentError(
	"Virtual column extension type expects an empty string as metadata".to_owned(),
	))
	}
	match metadata {
	Some(&"") => Ok(""),
	_ => Err(ArrowError::InvalidArgumentError(
	"Virtual column extension type expects an empty string as metadata".to_owned(),
	)),
	}

or even

Suggested change

	if metadata.is_some_and(str::is_empty) {
	Ok("")
	} else {
	Err(ArrowError::InvalidArgumentError(
	"Virtual column extension type expects an empty string as metadata".to_owned(),
	))
	}
	if let Some(&"") = metadata {
	return Ok("");
	};
	Err(ArrowError::InvalidArgumentError(
	"Virtual column extension type expects an empty string as metadata".to_owned(),
	))