Struct q_compress::Prefix

pub struct Prefix<T> where
    T: NumberLike,  {
    pub count: usize,
    pub code: Vec<bool>,
    pub lower: T,
    pub upper: T,
    pub run_len_jumpstart: Option<usize>,
}

A pairing of a Huffman code with a numerical range.

Quantile Compression works by splitting the distribution of numbers into ranges and associating a Huffman code (a short sequence of bits) with each range. The combination of these pieces of information, plus a couple others, is called a Prefix. When compressing a number, the compressor finds the prefix containing it, then writes out its Huffman code, optionally the number of consecutive repetitions of that number if run_length_jumpstart is available, and then the exact offset within the range for the number.

Fields

count: usize

The count of numbers in the chunk that fall into this Prefix’s range.

code: Vec<bool>

The Huffman code for this prefix. Collectively, all the prefixes for a chunk form a binary search tree (BST) over these Huffman codes. The BST over Huffman codes is different from the BST over numerical ranges.

lower: T

The lower bound for this prefix’s numerical range.

upper: T

The upper bound (inclusive) for this prefix’s numerical range.

run_len_jumpstart: Option<usize>

A parameter used for the most common prefix in a sparse distribution. For instance, if 90% of a chunk’s numbers are exactly 77, then the prefix for the range [0, 0] will have a run_len_jumpstart. The jumpstart value tunes the varint encoding of the number of consecutive repetitions of the prefix.

Trait Implementations

impl<T: Clone> Clone for Prefix<T> where
    T: NumberLike, 

fn clone(&self) -> Prefix<T>

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<T: Debug> Debug for Prefix<T> where
    T: NumberLike, 

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<T: NumberLike> Display for Prefix<T>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<T: PartialEq> PartialEq<Prefix<T>> for Prefix<T> where
    T: NumberLike, 

fn eq(&self, other: &Prefix<T>) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Prefix<T>) -> bool

This method tests for !=.

impl<T: Eq> Eq for Prefix<T> where
    T: NumberLike, 

impl<T> StructuralEq for Prefix<T> where
    T: NumberLike, 

impl<T> StructuralPartialEq for Prefix<T> where
    T: NumberLike,