Module twcs 

Modules

units 🔒

Unit-based compaction picks for one TWCS window.

Structs

Candidate 🔒

Metrics of a candidate compaction input, accumulated one file at a time.

CandidateScore 🔒

Score of a candidate compaction input. Higher is better: first by the predicted net file count reduction, then by the number of files participating in an overlap, then by smaller input bytes.

OrderedFile 🔒

TwcsCandidates 🔒

Discovery snapshot retained until the scheduler chooses its alternatives. Only selected candidates incur tombstone checks and pick-result logging.

TwcsPickMetrics 🔒

Cloneable planning metric handles, shared with spawned window evaluations.

TwcsPicker

TwcsPicker picks files of which the max timestamp are in the same time window as compaction candidates.

Window 🔒

WindowCandidate 🔒

A discovered alternative, not yet selected or admitted by the scheduler.

WindowOutputContext 🔒

WindowPick 🔒

Compaction inputs picked for one window.

WindowPickContext 🔒

Snapshot-wide inputs shared by each independent window strategy.

Enums

PickClass 🔒

Scheduling priority of a window’s pick. Earlier classes are scheduled first, and newer windows first within a class.

Constants

CLOSED_MERGE_INPUT_FACTOR 🔒

A closed merge in an inactive window may take this many times MAX_INPUT_FILES. Resolving overlaps across a whole window needs all of its overlapping files at once, and each byte is rewritten once per window.

DEFAULT_MAX_INPUT_FILES 🔒

Default maximum number of input SST files in one compaction input.

LEVEL_COMPACTED 🔒

MAX_INPUT_FILES_ENV 🔒

MAX_L1_L0_ROW_RATIO 🔒

A mixed L0/L1 compaction may rewrite at most this many L1 rows per L0 row.

Statics

MAX_INPUT_FILES 🔒

Maximum number of input SST files in one compaction input. Configurable via MAX_INPUT_FILES_ENV.

Functions

assign_to_windows 🔒

Assigns files to windows with predefined window size (in seconds) by their max timestamps.

find_active_window_by_sequence 🔒

Finds the active window from the file with the highest sequence number.

find_latest_window_in_seconds 🔒

Finds the latest active writing window among all files. Returns None when there are no files.

is_balanced_candidate 🔒

is_quiet_window 🔒

Whether the region has written at least as many rows as files hold, and at least one row, since the newest of them was written. Sequences are assigned per row and compaction keeps the inputs’ maximum, so this needs no state. Files written before row counts were recorded have zero rows, so a window holding them is not quiet.

is_settling_window 🔒

Whether window is the one right before active_window, where late data still lands.

log_pick_result 🔒

ordered_files 🔒

Flattens sorted runs into files ordered by (start asc, end desc), breaking ties by run and position to keep the order deterministic.

parse_max_input_files 🔒

pick_candidate_files 🔒

pick_count_first 🔒

Picks a contiguous (in global time order) interval of files to compact.

pick_count_first_where 🔒

pick_inactive_l0 🔒

Absorbs L0 files of an inactive window, in order of preference:

pick_mixed_within_budget 🔒

Mixed-level fallback for inactive windows: bypasses the balance checks but bounds the total rewrite to the output file budget.

pick_unbalanced_count_first 🔒

Last-resort pick for inactive windows with no balance requirement at all. Callers must only pass single-level (L0) files so the rewrite stays bounded by their bytes.

selected_overlaps_unselected 🔒

time_window_intersects_range 🔒

time_window_start 🔒

Uses the same half-open windows as memtables, including timestamps in the first second after a boundary. An unrepresentable window start is clamped to i64::MIN.

window_has_overlap 🔒

Type Aliases

CandidatePicker 🔒