Enum CompressionType 

#[non_exhaustive]
pub enum CompressionType {
    None,
    Lz4,
    Zstd(i32),
    ZstdDict {
        level: i32,
        dict_id: u32,
    },
}

Compression algorithm to use

Variants (Non-exhaustive)

Non-exhaustive enums could have additional variants added in future. Therefore, when matching against variants of non-exhaustive enums, an extra wildcard arm must be added to account for any future variants.

None

No compression

Not recommended.

Lz4

LZ4 compression

Recommended for use cases with a focus on speed over compression ratio.

Zstd(i32)

Zstd compression

Provides significantly better compression ratios than LZ4 with reasonable decompression speed (~1.5 GB/s).

Compression level can be adjusted (1-22, default 3):

• 1 optimizes for speed
• 3 is a good default (recommended)
• 9+ optimizes for compression ratio

Recommended for cold/archival data where compression ratio matters more than raw speed.

ZstdDict

Zstd compression with a pre-trained dictionary

Uses a pre-trained dictionary for significantly better compression ratios on small blocks (4–64 KiB), especially when data has recurring patterns.

level is the compression level (1–22), dict_id identifies the dictionary (truncated xxh3 hash of the dictionary bytes). The actual dictionary must be provided via Config or the relevant writer/reader.

Fields

level: i32

Compression level (1–22)

dict_id: u32

Dictionary fingerprint for mismatch detection

Implementations

impl CompressionType

pub fn dict_id(&self) -> u32

Returns the zstd dictionary id encoded in this compression configuration, or 0 when no dictionary applies. Used to populate crate::table::block::BlockIdentity::dict_id from a CompressionType at the call site without each caller re-doing the ZstdDict { dict_id, .. } destructure.

pub fn zstd(level: i32) -> Result<Self>

Create a zstd compression configuration with a checked level.

This is the recommended way to construct a CompressionType::Zstd value, as it validates the level before any I/O occurs.

Errors

Returns an error if level is outside the valid range -128..=22 (zstd negative “fast” levels and 0 = default are accepted; the on-disk format stores the level in one signed byte).

pub fn zstd_dict(level: i32, dict_id: u32) -> Result<Self>

Create a zstd dictionary compression configuration with checked level.

The dict_id should come from ZstdDictionary::id to ensure consistency between the compression type stored on disk and the dictionary used at runtime.

Errors

Returns an error if level is outside the valid range -128..=22 (zstd negative “fast” levels and 0 = default are accepted; the on-disk format stores the level in one signed byte).

Trait Implementations

impl Clone for CompressionType

fn clone(&self) -> CompressionType

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for CompressionType

impl Debug for CompressionType

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

Formats the value using the given formatter.

impl Display for CompressionType

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

Formats the value using the given formatter.

impl Eq for CompressionType

impl PartialEq for CompressionType

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

Tests for self and other values to be equal, and is used by ==.

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

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

impl StructuralPartialEq for CompressionType