Struct q_compress::CompressorConfig

pub struct CompressorConfig {
    pub compression_level: usize,
    pub delta_encoding_order: usize,
}

All the settings you can specify about compression.

Some, like delta_encoding_order, are explicitly stored as Flags in the compressed bytes. Others, like compression_level, affect compression but are not explicitly stored in the output.

Fields

compression_level: usize

compression_level ranges from 0 to 12 inclusive, defaulting to 6.

The compressor uses up to 2^compression_level prefixes.

For example,

• Level 0 achieves a modest amount of compression with 1 prefix and can be twice as fast as level 6.
• Level 6 achieves nearly the best compression with 64 prefixes and still runs in reasonable time. In some cases, its compression ratio is 3-4x as high as level level 0’s.
• Level 12 can achieve a few % better compression than 6 with 4096 prefixes but runs ~10x slower in many cases.

delta_encoding_order: usize

delta_encoding_order ranges from 0 to 7 inclusive, defaulting to 0.

It is the number of times to apply delta encoding before compressing. For instance, say we have the numbers [0, 2, 2, 4, 4, 6, 6] and consider different delta encoding orders.

• 0 indicates no delta encoding, it compresses numbers as-is. This is perfect for columnar data were the order is essentially random.
• 1st order delta encoding takes consecutive differences, leaving [0, 2, 0, 2, 0, 2, 0]. This is perfect for continuous but noisy time series data, like stock prices.
• 2nd order delta encoding takes consecutive differences again, leaving [2, -2, 2, -2, 2, -2]. This is perfect for locally linear data, like a sequence of timestamps sampled approximately periodically.
• Higher-order delta encoding is good for time series that are very smooth, like temperature or light sensor readings.

Trait Implementations

impl Clone for CompressorConfig

fn clone(&self) -> CompressorConfig

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for CompressorConfig

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

Formats the value using the given formatter.

impl Default for CompressorConfig

fn default() -> Self

Returns the “default value” for a type.

impl From<&'_ CompressorConfig> for Flags

fn from(config: &CompressorConfig) -> Self

Performs the conversion.