Struct CompactionPicker 

pub struct CompactionPicker { /* private fields */ }

Hybrid compaction picker combining TWCS and size-tiered strategies.

The picker operates in two passes:

1. TWCS pass — groups segments by (shard_id, measurement) and triggers compaction when the count exceeds count_trigger_threshold.

2. Size-tiered pass — within each (shard_id, measurement) group, classifies segments by SizeTier and triggers merges when a tier’s count exceeds size_tier_threshold.

The CompactionPolicy selects which passes run:

• Twcs → TWCS pass only
• SizeTiered → size-tiered pass only
• Hybrid → both passes, TWCS first (deduplicates tasks)

Implementations

impl CompactionPicker

pub fn new(trigger_threshold: usize) -> Self

Create a picker with the given count-based trigger threshold.

Uses the default policy with Hybrid strategy.

pub fn with_policy(policy: CompactionPolicy) -> Self

Create a picker from an explicit CompactionPolicy.

pub fn policy(&self) -> &CompactionPolicy

Returns the active compaction policy.

pub fn trigger_threshold(&self) -> usize

Returns the count-based trigger threshold.

pub fn pick( &self, segments: &[SegmentCatalogEntry], output_dir: &Path, ) -> Vec<CompactionTask>

Scan a set of segments and produce compaction tasks.

Uses the configured policy to run TWCS, size-tiered, or hybrid compaction. Groups segments by (shard_id, measurement).

Segments in Compacting or SoftDeleted state should be filtered out before calling this method.

pub fn pick_level( &self, segments: &[SegmentCatalogEntry], output_dir: &Path, source_level: CompactionLevel, ) -> Vec<CompactionTask>

Scan segments at a specific compaction level and produce tasks.

Enables multi-level compaction (L0→L1, L1→L2).

pub fn backpressure_delay_ms(&self, l0_count: usize) -> u64

Check if write backpressure should be applied.

Returns a throttle factor: 0 = no throttle, >0 = delay in milliseconds per write. Escalates linearly as L0 count grows beyond 4 × trigger_threshold.

Trait Implementations

impl Clone for CompactionPicker

fn clone(&self) -> CompactionPicker

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for CompactionPicker

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

Formats the value using the given formatter.

impl Default for CompactionPicker

fn default() -> CompactionPicker

Returns the “default value” for a type.