lsm_tree/compaction/
mod.rs

1// Copyright (c) 2024-present, fjall-rs
2// This source code is licensed under both the Apache 2.0 and MIT License
3// (found in the LICENSE-* files in the repository)
4
5//! Contains compaction strategies
6
7pub(crate) mod fifo;
8pub(crate) mod leveled;
9// pub(crate) mod maintenance;
10pub(crate) mod drop_range;
11mod flavour;
12pub(crate) mod major;
13pub(crate) mod movedown;
14pub(crate) mod pulldown;
15pub(crate) mod state;
16pub(crate) mod stream;
17// pub(crate) mod tiered;
18pub(crate) mod worker;
19
20pub use fifo::Strategy as Fifo;
21pub use leveled::Strategy as Leveled;
22// pub use tiered::Strategy as SizeTiered;
23
24pub use {fifo::NAME as FIFO_COMPACTION_NAME, leveled::NAME as LEVELED_COMPACTION_NAME};
25
26/// Alias for `Leveled`
27pub type Levelled = Leveled;
28
29#[doc(hidden)]
30pub use movedown::Strategy as MoveDown;
31
32#[doc(hidden)]
33pub use pulldown::Strategy as PullDown;
34
35use crate::{
36    compaction::state::CompactionState, config::Config, version::Version, HashSet, KvPair, TableId,
37};
38
39/// Input for compactor.
40///
41/// The compaction strategy chooses which tables to compact and how.
42/// That information is given to the compactor.
43#[derive(Debug, Eq, PartialEq)]
44pub struct Input {
45    /// Tables to compact
46    pub table_ids: HashSet<TableId>,
47
48    /// Level to put the created tables into
49    pub dest_level: u8,
50
51    /// The logical level the tables are part of
52    pub canonical_level: u8,
53
54    /// Table target size
55    ///
56    /// If a table merge reaches the size threshold, a new table is started.
57    /// This results in a sorted "run" of tables.
58    pub target_size: u64,
59}
60
61/// Describes what to do (compact or not)
62#[derive(Debug, Eq, PartialEq)]
63pub enum Choice {
64    /// Just do nothing.
65    DoNothing,
66
67    /// Moves tables into another level without rewriting.
68    Move(Input),
69
70    /// Compacts some tables into a new level.
71    Merge(Input),
72
73    /// Delete tables without doing compaction.
74    ///
75    /// This may be used by a compaction strategy that wants to delete old data
76    /// without having to compact it away, like [`fifo::Strategy`].
77    Drop(HashSet<TableId>),
78}
79
80/// Trait for a compaction strategy
81///
82/// The strategy receives the levels of the LSM-tree as argument
83/// and emits a choice on what to do.
84#[expect(clippy::module_name_repetitions)]
85pub trait CompactionStrategy {
86    /// Gets the compaction strategy name.
87    fn get_name(&self) -> &'static str;
88
89    #[doc(hidden)]
90    fn get_config(&self) -> Vec<KvPair> {
91        vec![]
92    }
93
94    /// Decides on what to do based on the current state of the LSM-tree's levels
95    fn choose(&self, version: &Version, config: &Config, state: &CompactionState) -> Choice;
96}
lsm_tree/compaction/mod.rs

lsm_tree/compaction/
mod.rs
