Struct q_compress::Flags

#[non_exhaustive]
pub struct Flags {
    pub use_5_bit_code_len: bool,
    pub delta_encoding_order: usize,
    pub use_min_count_encoding: bool,
    pub use_gcds: bool,
    pub use_wrapped_mode: bool,
}

The configuration stored in a Quantile-compressed header.

During compression, flags are determined based on your CompressorConfig and the q_compress version. Flags affect the encoding of the rest of the file, so decompressing with the wrong flags will likely cause a corruption error.

You will not need to manually instantiate flags; that should be done internally by Compressor::from_config. However, in some circumstances you may want to inspect flags during decompression.

Fields (Non-exhaustive)

Non-exhaustive structs could have additional fields added in future. Therefore, non-exhaustive structs cannot be constructed in external crates using the traditional Struct { .. } syntax; cannot be matched against without a wildcard ..; and struct update syntax will not work.

use_5_bit_code_len: bool

Whether to use 5 bits to encode the length of a prefix Huffman code, as opposed to 4. The first versions of q_compress used 4, which was insufficient for Huffman codes that could reach up to 23 in length (23 >= 16 = 2^4) in spiky distributions with high compression level. In later versions, this flag is always true.

Introduced in 0.5.0.

delta_encoding_order: usize

How many times delta encoding was applied during compression. This is stored as 3 bits to express 0-7. See CompressorConfig for more details.

Introduced in 0.6.0.

use_min_count_encoding: bool

Whether to use the minimum number of bits to encode the count of each prefix, rather than using a constant number of bits. This can reduce file size slightly for small data. In later versions, this flag is always true.

Introduced in 0.9.1.

use_gcds: bool

Whether to enable greatest common divisor multipliers for each prefix. This adds an optional multiplier to each prefix metadata, so that each unsigned number is decoded as x = prefix_lower + offset * gcd. This can improve compression ratio in some cases, e.g. when the numbers are all integer multiples of 100 or all integer-valued floats.

Introduced in 0.10.0.

use_wrapped_mode: bool

Whether to release control to a wrapping columnar format. This causes q_compress to omit count and compressed size metadata and also break each chuk into finer data pages.

Introduced in 0.11.2.

Trait Implementations

impl Clone for Flags

fn clone(&self) -> Flags

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for Flags

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

Formats the value using the given formatter.

impl PartialEq<Flags> for Flags

fn eq(&self, other: &Flags) -> bool

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

fn ne(&self, other: &Rhs) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl TryFrom<Vec<bool, Global>> for Flags

type Error = QCompressError

The type returned in the event of a conversion error.

fn try_from(bools: Vec<bool>) -> QCompressResult<Self>

Performs the conversion.

impl TryInto<Vec<bool, Global>> for &Flags

type Error = QCompressError

The type returned in the event of a conversion error.

fn try_into(self) -> QCompressResult<Vec<bool>>

Performs the conversion.

impl Eq for Flags

impl StructuralEq for Flags

impl StructuralPartialEq for Flags