Struct DeltaScheme 

pub struct DeltaScheme { /* private fields */ }

FastLanes Delta encoding for smooth / near-monotone integers.

Delta replaces each value with its difference from an earlier value (at the FastLanes lane stride), so a later cascade layer (FoR / BitPacking) packs the smaller residuals. It only pays off when those residuals span meaningfully fewer bits than the values themselves.

The minimum penalized compression ratio required for Delta to be selected is configurable via DeltaScheme::new; DeltaScheme::default uses a ratio of 1.25.

Implementations

impl DeltaScheme

pub const fn new(min_ratio: f64) -> Self

Creates a Delta scheme requiring min_ratio after the delta penalty before it wins.

Pass a higher ratio to make Delta more conservative, or a lower one to select it more eagerly. DeltaScheme::default uses a ratio of 1.25.

Trait Implementations

impl Clone for DeltaScheme

fn clone(&self) -> DeltaScheme

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for DeltaScheme

impl Debug for DeltaScheme

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

Formats the value using the given formatter.

impl Default for DeltaScheme

fn default() -> Self

Returns the “default value” for a type.

impl PartialEq for DeltaScheme

fn eq(&self, other: &DeltaScheme) -> 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 Scheme for DeltaScheme

fn descendant_exclusions(&self) -> Vec<DescendantExclusion>

Delta-encode the data at most once per path: exclude Delta from the subtrees of both the bases and the deltas children so we never delta-encode data that was already delta-encoded.

fn ancestor_exclusions(&self) -> Vec<AncestorExclusion>

Delta over dictionary codes just adds indirection: codes are compact integers with no monotone structure, so (like FoR/Sequence) skip the codes child.

fn scheme_name(&self) -> &'static str

The globally unique name for this scheme (e.g. "vortex.int.bitpacking").

fn matches(&self, canonical: &Canonical) -> bool

Whether this scheme can compress the given canonical array.

fn num_children(&self) -> usize

The number of child arrays this scheme produces when cascading. Returns 0 for leaf schemes that produce a final encoded array.

fn expected_compression_ratio( &self, data: &ArrayAndStats, compress_ctx: CompressorContext, _exec_ctx: &mut ExecutionCtx, ) -> CompressionEstimate

Cheaply estimate the compression ratio for this scheme on the given array.

fn compress( &self, compressor: &CascadingCompressor, data: &ArrayAndStats, compress_ctx: CompressorContext, exec_ctx: &mut ExecutionCtx, ) -> VortexResult<ArrayRef>

Compress the array using this scheme.

fn stats_options(&self) -> GenerateStatsOptions

Returns the stats generation options this scheme requires. The compressor merges all eligible schemes’ options before generating stats so that a single stats pass satisfies every scheme.

impl StructuralPartialEq for DeltaScheme