Skip to content

parquet: reduce clone in delta byte array decoder #9282

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
Dandandan merged 1 commit into from
Jan 31, 2026
Merged

parquet: reduce clone in delta byte array decoder #9282

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
15 changes: 8 additions & 7 deletions parquet/src/encodings/decoding.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -1008,7 +1008,8 @@ pub struct DeltaByteArrayDecoder<T: DataType> {
suffix_decoder: Option<DeltaLengthByteArrayDecoder<ByteArrayType>>,

// The last byte array, used to derive the current prefix
previous_value: Vec<u8>,
// Stored as Bytes to avoid clone allocation when creating output
previous_value: Bytes,

// Number of values left
num_values: usize,
Expand All @@ -1030,7 +1031,7 @@ impl<T: DataType> DeltaByteArrayDecoder<T> {
prefix_lengths: vec![],
current_idx: 0,
suffix_decoder: None,
previous_value: vec![],
previous_value: Bytes::new(),
num_values: 0,
_phantom: PhantomData,
}
Expand All @@ -1053,7 +1054,7 @@ impl<T: DataType> Decoder<T> for DeltaByteArrayDecoder<T> {
self.suffix_decoder = Some(suffix_decoder);
self.num_values = num_prefixes;
self.current_idx = 0;
self.previous_value.clear();
self.previous_value = Bytes::new();
Ok(())
}
_ => Err(general_err!(
Expand Down Expand Up @@ -1081,14 +1082,14 @@ impl<T: DataType> Decoder<T> for DeltaByteArrayDecoder<T> {
let prefix_len = self.prefix_lengths[self.current_idx] as usize;

// Concatenate prefix with suffix
let mut result = Vec::new();
let mut result = Vec::with_capacity(prefix_len + suffix.len());
Copy link
Contributor

@alamb alamb Jan 30, 2026

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

makes sense to allocate the correct size.

result.extend_from_slice(&self.previous_value[0..prefix_len]);
result.extend_from_slice(suffix);

let data = Bytes::from(result.clone());
Copy link
Contributor

@alamb alamb Jan 30, 2026

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

this certainly seems to save a clone. Looks good to me 👍

item.set_from_bytes(data);
let data = Bytes::from(result);
item.set_from_bytes(data.clone());

self.previous_value = result;
self.previous_value = data;
self.current_idx += 1;
}

Expand Down
Loading