alkblobs/tasks/store-sweep-durable-window.md at 758ccfb359a724984fdc6a707fdbdf0727efa7e6

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glm-5.3-flash 758ccfb359 docs(tasks): decompose wave 3 — the sqlite kv engine, the durable delete window, the first SQL-backed column

Six tasks against the wave-2 contract surface as reviewed (no
amendments from the gate):

- engine-sqlite: the default kv engine — WAL + synchronous=NORMAL,
  prepared statements, the indexed size column probe (B5's row shape),
  has-as-EXISTS, virgin-store no-tables-yet tolerance, spawn_blocking
  discipline
- engine-sqlite-window: the engine-state seam's window family only
  (ADR-012 §5's reduction — gc_window, stage/take; no pin rows, no
  sweep-lock body)
- store-sqlite-construction: KvEngine::Sqlite slots in, the
  dual-tier/kv-only constructors with the constructor-tunable window
  delay (default 5 min), ensure_gc_schema at construction, the
  one-window-host posture
- store-sweep-durable-window: the sweep's SQL-backed form — overdue
  rows execute with re-arbitration before/alongside marking, candidates
  stage at mark_end + window, counts exact relative to the schedule
  (ADR-012 §6.7); the inline form preserved verbatim
- suite-column-sqlite: the first SQL-backed column, server-less —
  form-independent reference rows mirror directly; the sweep rows are
  schedule-relative (the recorded INV-4/5 mirror amendment)
- review-wave-3: the engine-wave gate (engine-vs-contract conformance)

Verification: dependency graph validated (all ids resolve, no cycles,
topological order clean); docs-only change.

Refs: docs/plans/implementation.md §Wave 3

2026-10-11 23:48:23 +00:00

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Description

Grow the sweep's SQL-backed form (ADR-008 §2; ADR-012 §5/§6.7) beside the inline form in src/store.rs — the first durable delete window, single-node:

The branch: the sweep runs the durable form when the kv engine hosts the window (sqlite — the one-window-host posture); the inline form is preserved verbatim for non-SQL engines (mem/local — the wave-2 sweep tests stay green unchanged). The branch keys off the engine representation (the KvEngine match), never off a flag.
The single-node posture is unchanged (ADR-008 §2): pins, RAII guards, and the arbitration lock stay in-process (GcHome) — only the persistence of the delete window (the staged-candidate table) is engine rows.
The durable form's protocol (per sweep, under the lease):
1. Execute overdue (before/alongside marking — ADR-012 §6.7): window_take(now) returns the overdue keys; each is re-arbitrated at execution time through the same arbitrated_delete path and deleted in batches. The protect- consult posture on this path is a recorded design point (the sweep's protect consult covers its execution phase — the same reasoning that keeps the inline form's candidates at consult_protect = false). A vanished candidate (deleted during the delay by a direct delete) settles into the cancelled count — the vanished-candidate accounting carries over.
2. Mark: enumerate the pool, compute the live set, compute the candidate-dead set (unchanged).
3. Stage: window_stage(candidates) at visible_after = mark_end + window — the constructor-tunable delay (ADR-008 §2; the store carries the value its constructor took).
4. Report: candidates_staged = candidates staged this sweep; deleted/cancelled_by_arbitration = the executed overdue set. Exact-count invariants are asserted relative to this schedule (ADR-012 §6.7) — staged-this-sweep and executed-this-sweep are different sets (the delay separates them); the suite's sqlite column asserts the two-sweep shapes (suite-column-sqlite).
Abort shapes unchanged: NoLivenessSources/ProtectFailed/ SweeperLock abort before anything is staged or executed (nothing deleted, Ok(SweepReport)); operational failures (engine I/O) are the Err half (ADR-012 §1).
The sweep-vs-put race under the durable form: a put landing during the window delay pins in-process (pin-before-publish); the execution-time re-arbitration sees the pin and cancels the candidate — the test-asserted property (a visible entry is never deleted while liveness protects it; an in-flight put is never deleted by a sweep started before it committed) holds across the delay, and is unit-tested in that form.
Unit tests in store.rs: two-sweep exact-count shapes (sweep 1 stages N at delay 0 → sweep 2 executes exactly N — deleted + cancelled == N against the staged set); the race across the delay (put during the window survives; the unpinned twin deletes); the abort shapes on a sqlite store; the vanished-candidate form; the inline form untouched (the mem/local suites stay green).

Acceptance Criteria

The sweep branches on window hosting; the inline form's behavior and its wave-2 tests unchanged
Durable form: overdue rows execute with execution-time re-arbitration before/alongside marking; candidates stage at visible_after = mark_end + window
Report counts exact relative to the schedule (unit-tested two-sweep shapes); aborts delete nothing
The race property unit-tested across the delay (a put landing during the window survives the next sweep's execution)
The protect-consult posture on overdue execution recorded
cargo test (default) green; cargo clippy --all-targets -- -D warnings and cargo fmt --check green

References

src/store.rs (the sweep — sweep/sweep_window/arbitrated_delete)
docs/architecture/decisions/005-pooled-cas-and-gc-mechanism.md (§Sweep — the protocol)
docs/architecture/decisions/008-trait-size-probe-fleet-gc-and-large-engines.md §2 (the staged re-arbitrated delete; the delay)
docs/architecture/decisions/012-pre-decomposition-consistency-rulings.md §1 (abort-as-data), §5 (single-node posture unchanged), §6.7 (the executor is the next sweep)
docs/architecture/decisions/013-family-composition-reactive-boundary-and-feature-graph.md §2 (the lease semantics)
src/gc.rs (GcHome arbitration; EngineWindowState the store core calls)

Notes

To be filled by implementation agent

Summary

To be filled on completion

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