Trait CompactionStrategy 

pub trait CompactionStrategy: Send + Sync {
    // Required methods
    fn get_name(&self) -> &'static str;
    fn choose(
        &self,
        version: &Version,
        config: &Config,
        state: &CompactionState,
    ) -> Choice;

    // Provided methods
    fn pending_compaction_bytes(&self, _version: &Version) -> u64 { ... }
    fn next_merge_level(
        &self,
        version: &Version,
        dest_level: u8,
    ) -> Option<usize> { ... }
}

Trait for a compaction strategy

The strategy receives the levels of the LSM-tree as argument and emits a choice on what to do.

Required Methods

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

Gets the compaction strategy name.

fn choose( &self, version: &Version, config: &Config, state: &CompactionState, ) -> Choice

Decides on what to do based on the current state of the LSM-tree’s levels

This is the purely structural decision (level shape, run counts, size targets); it deliberately does not see the live runtime config. The orchestrator layers the runtime-config-driven housekeeping fallback on top (the density-based columnar rewrite).

Provided Methods

fn pending_compaction_bytes(&self, _version: &Version) -> u64

Estimated bytes pending compaction: on-disk data currently sitting above its level’s target size that must eventually be rewritten downward (a RocksDB estimate-pending-compaction-bytes analog). A scheduler / tiering consumer reads it as a compaction-debt signal; 0 means the tree is at or below its target shape.

The default is 0 for strategies without a size-target notion of debt (FIFO, major one-shot); the leveled strategy overrides it with the per-level overflow sum.

fn next_merge_level(&self, version: &Version, dest_level: u8) -> Option<usize>

The level a merge into dest_level writes outputs that are next merged into, whose table boundaries they are cut on (see Config::compaction_output_alignment); None cuts them at the target size alone.

The default is the first level below the destination that holds tables: outputs move down through empty levels untouched and are next merged where tables are, as a leveled intra-L0 merge’s outputs are merged into the base level. A strategy whose outputs are next merged elsewhere, such as back into the level they were written to, overrides it.

Dyn Compatibility

This trait is dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety".

Implementors

impl CompactionStrategy for lsm_tree::compaction::Fifo

impl CompactionStrategy for lsm_tree::compaction::Leveled

impl CompactionStrategy for lsm_tree::compaction::EccHeal

impl CompactionStrategy for lsm_tree::compaction::planned::Strategy

impl CompactionStrategy for lsm_tree::compaction::SizeTiered