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fix(db): keep rows discarded by cleanup cleared after a restart; build GC oracle reach from constructed histories - #2382
Fixed: a row discarded by an explicit cleanup came back after a restart.collection.cleanup() discards the rows of transactions that are still persisting. Earlier decisions (the pr-2258-gc-retention reviews) say that those rows stay cleared. The fix in #2258 skipped a discarded transaction's rows only while the Collection was cleaning up or cleaned up. After a subscribe restarted the Collection, the next write recomputed the optimistic state and showed the discarded row again. Now state.cleanup() records the transactions it discards, and the optimistic overlay skips exactly those transactions. Transactions that start after the cleanup show their rows as before.
Law: a row that an explicit cleanup discards stays cleared through a restart and later writes, until its transaction settles. Authority: docs/contributing/oracle-reviews/pr-2258-gc-retention-round3.md ("Cleanup starts by discarding public rows"; "restart after GC owes no discarded-draft restoration") and the fix(db): keep a collection from garbage collection while its transaction persists #2258 repair of row resurrection after explicit cleanup.
RED: on main, the extended oracle fails at fixed seed 20261024 (shrunk: insert b, cleanup b, subscribe b, insert b, settle complete). At the second insert, the model owes keys [2] and production shows [1, 2]. Random seeds -277388568 and -1002447957 fail the same way.
GREEN: the oracle passes at the default seeds and seeds 1 to 5. Seven neighboring GC and optimistic oracles pass (369 tests), and the full packages/db suite passes (396 files, 52,079 tests).
Mutant: with the old guard restored, the oracle fails at the same step.
Size: about +31 B gzip for the minified packages/db build. pnpm size:compare could not run here, because it installs dependencies in its baseline worktree.
Oracle extensions that found it: the oracle now generates an explicit cleanup step in the middle of a history. It declares reach states for a settlement, an unsubscribe, a restart, and a write after a cleanup. A Collection's settlement-restart functions in transactions.ts are owned. A 1 ms clock step checks one millisecond before a deadline. A transition-table version of this model (a prototype, not in this PR) showed that the old grammar never fired the transitions after a cleanup.
The garbage-collection transaction oracle (collection-gc-transaction-oracle.property.test.ts) now runs on oracleProperty, and its reach comes from constructed histories. Before this change, it ran a raw fc.assert campaign with a reach floor of 1, so its reach depended on the seed. At seed -977831430, its random campaign never entered settled-while-subscribed and failed on reach alone. No law failed.
The law, its authority, the model's rules, the production driver's operations, and the comparison do not change. The property id, the fixed seed 20261024, and the run budget of 100 also stay the same.
Constructed histories: seven builders, at least one for each of the seven required states, replace the literal histories that this PR first used. Each builder opens with the steps that enter its state and keeps the generated steps after them. So the rest of the history stays random, and half of each campaign's histories are constructed. Only constructed histories gate reach, and every campaign runs each one once.
Plan and model:resolve(history) turns each history into a legal plan with handler ids and drain steps. The model computes the expected snapshot after each action from that plan, and the driver only records each Collection's status and rows.
Docs: the replay comment and the coverage-map entry describe the constructed histories. A stale test-name pattern for this property leaves the replay manifest.
An earlier commit on this branch added literal fixed histories instead. A review showed that they were not declared to the reach. The maintainer then said that reach must keep randomness, which is what constructed histories give.
🔬 Oracle Coverage
Law: unchanged. Garbage collection retires a Collection only after gcTime with no subscriber and no persisting transaction. Authority: BaseCollectionConfig.gcTime and the persisting-transaction hold in lifecycle.ts, as the oracle's prose states.
Reach: with constructed histories included, the fixed seed enters each required state 10 to 31 times, and the random campaign at seed -977831430 enters each 13 to 39 times.
RED:TANSTACK_DB_ORACLE_SEED=-977831430 pnpm --filter @tanstack/db exec vitest run tests/collection-gc-transaction-oracle.property.test.ts on main fails with settled-while-subscribed (0).
GREEN: the default run (fixed seed, random, and determinism) and the same seed pass. oracle-replay.test.ts passes 116 of 116 tests. pnpm lint:changed and the run-budget check report nothing.
Mutants:
A builder that returns its input unchanged fails with constructed history "settled while subscribed" did not enter settled-while-subscribed.
Production: when canGarbageCollect ignores subscribers, both generated campaigns fail on the retirement law.
Limits:
Each constructed history fixes the steps up to its state. A random part before them could leave a pending handler or a subscriber that stops the state from being entered.
The seed -977831430 trace is not kept as a fixed regression.
The constructed histories take the first replay path indexes, so a path that was recorded before this change selects a different history.
Retirement timing: retirement before gcTime is a violation. From gcTime to 20 ms after it, either outcome is allowed, because exact cleanup latency is not promised; after that, retirement is owed. A mutant that retires 2 ms early fails. A mutant that retires 1 ms early survives, because this harness cannot tell it apart from a retirement exactly at gcTime, which the law allows.
A settlement on a cleaned-up Collection that starts no GC delay is not publicly observable, so the law does not claim it. Writes into a cleaned-up Collection are not generated.
This was a follow-up from #2378, which found the reach failure during a full db run.
✅ Checklist
I have tested this code locally with pnpm test. I ran the changed oracle at the default and recorded seeds, both mutants, oracle-replay.test.ts, and pnpm lint:changed. A code review and a simplification pass ran on an earlier version of this branch.
🚀 Release Impact
This change affects published code, and I have generated a changeset (@tanstack/db: patch).
This change is docs/CI/dev-only (no release).
This pull request and its description were written by Isaac.
…ery reach state
The oracle's random campaign combined a raw fc.assert with a reach
floor, so whether it entered each declared state depended on the seed.
At seed -977831430 it never entered settled-while-subscribed and failed
on reach alone; no law failed.
Four constructed histories now enter all seven declared states in
every campaign, through the same model, production driver, and
comparison as the generated histories, with no expected answer of
their own.
- Law: unchanged (GC retires a Collection only after gcTime with no
subscriber and no persisting transaction). Authority: the oracle's
opening contract.
- Reach: every declared state in every campaign. With one generated
run per campaign, seeds -977831430, 1, 2 and 3 all reach every state.
- RED: TANSTACK_DB_ORACLE_SEED=-977831430 on the parent:
settled-while-subscribed (0).
- GREEN: the same seed, and the default fixed-seed and random
campaigns, pass.
- Mutant: without the first constructed history, the same seed fails
on settled-while-subscribed (0) again.
- Limits: the constructed histories fix reach, not grammar weights; the
random campaign's own distribution is unchanged.
Co-authored-by: Isaac <no-reply@databricks.com>
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The Collection GC property test now models and executes resolved histories, then compares per-action observations against predicted checkpoints. It includes constructed histories for declared reach states. The coverage documentation and replay manifest also change.
Changes: Collection GC transaction oracle
Layer / File(s)
Summary
Resolved history model packages/db/tests/collection-gc-transaction-oracle.property.test.ts
The test defines ID-addressed actions and reach states, models Collection state, resolves legal histories, and builds expected checkpoints.
History execution and checkpoint checks packages/db/tests/collection-gc-transaction-oracle.property.test.ts
The driver executes actions against real Collections and records cleanup status and visible keys. The checker compares observations with expected checkpoints and checks trace completeness.
Oracle campaign and supporting coverage packages/db/tests/collection-gc-transaction-oracle.property.test.ts, docs/contributing/oracle-coverage.md, packages/db/tests/oracle-replay-manifest.ts
The property runs 100 generated histories with fixed seed 20261024 and includes constructed histories for declared reach states. The documentation expands lifecycle and demand-change coverage details. The replay manifest removes the explicit test-name pattern for collection-lifecycle.gc-persisting-transaction.
TanStack/db#2258: This PR changes Collection retention for persisting transactions. The current property constructs histories that test retention, settlement, and cleanup behavior.
TanStack/db#2171: This PR changes transaction settlement observation. The current property drives commit and rollback and observes handler settlement.
TanStack/db#2237: This PR changes oracle replay selection and manifest handling. The current change registers the property with oracleProperty and removes its explicit replay test-name pattern.
Suggested reviewers:nabil372
Merge Risk: Low · previous review 7c939
The test’s description misstates its deadline constraint. Clarify it so maintainers can interpret the coverage correctly; the change is otherwise mergeable.
Pre-merge checks: 5
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The title identifies both the cleanup row-resurrection fix and the constructed-history GC oracle work. It is specific and related to the main changes.
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Comparing 43e9e3f35 (this PR) against babf94e33 (base). Write times are per-write medians over 100 iterations (20 warmup writes). Timings use the median of 3 fresh fixture repetition(s).
Overall median write time vs base: 1.00× · cold hydrate time: 0.96× (geometric mean of per-case ratios; lower is faster).
Writes: No significant changes (threshold: ±20% and >0.05ms).
Cold hydrate: 0 regression(s), 1 improvement(s) (threshold: ±50% and >5ms).
CI regression gate: PASS. Query geometric means: >+30% writes or >+50% cold. A case also fails when every repetition exceeds the entire base range by >+50% and the metric's absolute floor.
Per-case flags are noisy on shared runners. Read the geometric means first.
Writes
Query
Δ median write time (geomean)
Best case
Worst case
Flags
list: newest 50 open
+1.4%
-9.4%
+77.7%
—
list + author
-0.7%
-13.8%
+43.5%
—
list + comment count
-1.5%
-5.5%
+2.0%
—
list + 3 recent comments
-1.1%
-7.8%
+14.2%
—
issue detail + comments
-1.1%
-4.4%
+4.7%
—
open issues + documents
-1.0%
-4.8%
+3.2%
—
Cold hydrate
Query
Δ cold hydrate time (geomean)
Best case
Worst case
Flags
list: newest 50 open
-0.7%
-37.1%
+46.7%
—
list + author
-7.2%
-34.2%
+16.9%
—
list + comment count
+2.5%
-10.0%
+33.7%
—
list + 3 recent comments
-3.1%
-24.7%
+60.1%
—
issue detail + comments
-8.3%
-32.7%
+4.3%
—
open issues + documents
-11.3%
-53.1%
+67.5%
1 🟢
Each row aggregates that query's scale/index/write-mode configurations; per-configuration tables below.
Runner: node v24.8.0, linux 7.0.0-1017-azure, AMD EPYC 9V74 80-Core Processor. Timings on shared CI runners are noisy; treat small deltas as indicative only.
Review fixes for the constructed histories:
- The four histories are now declared fixed histories:
createOracleReach gets fixedHistories: 4 and the driver begins each
with beginHistory({ fixed: true }) (fast-check passes examples by
reference). The reach check now fails when no fixed history enters a
declared state, which is what makes reach independent of the seed;
before, that claim was unchecked.
- They attach through oraclePropertyOptions' examples option, the
documented entry point, instead of a separate wrapper, and are named
fixed histories, the glossary's term for literal histories.
- The first history advances 120 ms after its settlement, so it
observes that a subscriber still holds the Collection once the
transaction's hold ends.
- The comment names the states each history enters and no longer calls
a held Collection due; the replay comment notes that the fixed
histories take the first path indexes. The reach states are one list.
- The coverage map records the fixed histories and that the floor now
counts them.
Evidence:
- GREEN: the default campaigns and seed -977831430 pass.
- Mutant (fixed history): settling before subscribing in history 1
fails both campaigns: its 4 fixed histories did not enter
settled-while-subscribed.
- Mutant (production): canGarbageCollect without the subscriber check
fails both campaigns at fixed history 1, step 3 advance (a cleaned up
at 120 ms).
- Limits: reach counts fixed and generated histories together (the
framework's rule), so a floor of 1 does not show what the generated
histories reach alone.
Co-authored-by: Isaac <no-reply@databricks.com>
…stories
The four literal fixed histories made reach independent of the seed, but
they replaced the random histories that reach the states. Move the
campaign onto oracleProperty: seven constructed histories, one or more for
each required reach state, each open with the steps that enter its states
and keep the generated steps after them. Half of each campaign's histories
are constructed, so reach stays random after each state.
The law, the model's rules, and the production driver and comparison are
unchanged. The model now computes the expected snapshot after each
action from the plan (resolve drops steps the grammar does not generate),
and the driver only records the Collections' status and rows. The explicit
cleanup checkpoints compare both Collections, not only the cleaned one.
The property id, replay names, fixed seed 20261024, and run budget 100 are
kept. The replay manifest drops its stale test-name pattern, as the
framework's other oracleProperty owners do.
Law: unchanged. Automatic GC retires a Collection only after gcTime with no
subscriber and no persisting transaction; each persisting transaction holds
each Collection it touches; explicit cleanup() still retires it. Authority:
BaseCollectionConfig.gcTime and the persisting-transaction hold in
packages/db/src/collection/lifecycle.ts, as stated in the oracle's prose.
Reach: seven constructed histories enter the seven declared states. Fixed
seed 20261024 reach counts (constructed examples included): settled-while-
subscribed 10, gc-due-while-persisting 21, retired-after-completion 31,
retired-after-failure 24, retired-after-shared-settlement 15,
cleanup-while-persisting 19, restarted-after-retirement 31.
RED: origin/main (the parent, a86aa43), seed -977831430, random campaign:
"generated histories reached these states fewer than 1 times ...
settled-while-subscribed (0)".
GREEN: `pnpm exec vitest run tests/collection-gc-transaction-oracle.property.test.ts`
passes its fixed-seed, random, and determinism tests; the same with
TANSTACK_DB_ORACLE_SEED=-977831430 passes (random reach: settled-while-
subscribed 13, gc-due-while-persisting 20, retired-after-completion 31,
retired-after-failure 26, retired-after-shared-settlement 15,
cleanup-while-persisting 16, restarted-after-retirement 39).
oracle-replay.test.ts passes 116 of 116; `pnpm lint:changed` and
`pnpm lint:run-budgets` report nothing.
Mutant (builder): the "settled while subscribed" builder replaced with the
identity fails with "constructed history "settled while subscribed" did not
enter settled-while-subscribed".
Mutant (production): canGarbageCollect without the activeSubscribersCount
check fails both campaigns at "step 2 advance" and "step 3 advance" under
law retirement. The production file was restored (git diff clean).
Limits: the reach counts include the constructed examples, so they do not
show what the generated histories reach alone. The required steps open a
constructed history, so the history before each state is fixed; the random
part is the steps after it. Cleanup-while-persisting drops generated
settlements so its opening insert is still pending at cleanup. No
calibration was added (the literal version had none). The seed -977831430
trace is not kept as a fixed regression: the constructed histories now make
its reach hold, and its random history is not reproduced here.
Co-authored-by: Isaac <no-reply@databricks.com>
The cleanup builder returned an object literal whose end widened to
string, so Vitest's typecheck failed in every db test job on 245ea28
(TS2322 at the end literal). The builder now declares its History
return type.
RED: CI db-1, db-2, collections, and Test on 245ea28 (TypeCheckError
TS2322). GREEN: tsc reports no error in the oracle, and the oracle
passes.
Co-authored-by: Isaac <no-reply@databricks.com>
…ction functions
The GC transaction oracle judged only lifecycle.ts, but the settlement that
releases a persisting transaction's hold and restarts the gcTime delay lives in
Transaction.commit (completion), Transaction.rollback (failure), and
Transaction.touchCollection (the restart). Declare those three functions with
their static call trees, and record them in the coverage map.
Evidence block
- Law: a persisting transaction holds each Collection it touches, and its
settlement (completion or failure) restarts the gcTime delay. Authority: the
oracle header law; BaseCollectionConfig.gcTime; glossary `optimistic state`
and `cleanup`.
- Reach: grammar unchanged. Fixed seed 20261024: cleanup-while-persisting 19,
gc-due-while-persisting 21, restarted-after-retirement 31,
retired-after-completion 31, retired-after-failure 24,
retired-after-shared-settlement 15, settled-while-subscribed 10.
- RED: no observable behavior changed, so there is no RED for the declaration
itself. The hostile mutants below ran against the parent commit's production.
- GREEN: `npx vitest run --coverage.enabled=false
tests/collection-gc-transaction-oracle.property.test.ts` in packages/db passes
3/3 at default seeds and at TANSTACK_DB_ORACLE_SEED=1..5.
- Mutant, each applied alone to packages/db/src/transactions.ts and restored:
M4 completion does not restart (commit passes false): violated at
"step 4 advance" and "step 3 advance". M5 failure does not restart (rollback
passes false): violated at the same checkpoints. M6 only the first Collection
restarts: violated at "step 3 advance" and "step 5 advance".
- Limits: the owns entries name three functions, not every Transaction method.
Other Transaction paths are not claimed. Lint: pnpm lint:changed and
pnpm lint:oracles are clean.
Co-authored-by: Isaac <no-reply@databricks.com>
Retirement before gcTime is a violation. After the deadline, the 20/60/120 ms
grid accepts retirement only when the next checkpoint shows it, and exact
wall-clock cleanup latency is not promised. A mutant that retires at gcTime + 1
ms is indistinguishable from gcTime + 19 ms on this grid, so the oracle does not
claim finer timing. No clock steps were added. The model compares strictly at
the deadline, and whether a retirement at exactly gcTime is legal is left as a
maintainer decision, recorded in the coverage map.
Evidence block
- Law: automatic GC retires a Collection only after gcTime with no subscriber and
no persisting transaction. Authority: BaseCollectionConfig.gcTime; the
coverage-map GC retention boundaries entry, which says exact wall-clock cleanup
latency is not promised.
- Reach: unchanged (prose only). Fixed seed 20261024 and the seeds in the
previous commit are unchanged.
- RED: none. This commit changes prose and no behavior.
- GREEN: the oracle passes 3/3 at default seeds and seeds 1..5 (the same run as
the previous commit, with this text in place).
- Mutant, each applied alone to packages/db/src/collection/lifecycle.ts and
restored: delay gcTime - 1 is violated at "step 2 advance"; delay gcTime + 30
is violated at "step 0 advance"; delay gcTime + 1 SURVIVES, as the limit
predicts.
- Limits: a retirement later than gcTime but before the next checkpoint is not
separated from the deadline. The oracle does not judge cleanup-queue latency
beyond the next checkpoint. Whether a retirement exactly at gcTime is legal is
an open maintainer decision.
Co-authored-by: Isaac <no-reply@databricks.com>
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Actionable comments posted: 1
Fix comments: Fix CodeRabbit comments on this PR
Prompt to fix all issues
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Inline comments:
Review comments at
@packages/db/tests/collection-gc-transaction-oracle.property.test.ts:
- Around line 89-91: Update the boundary description in the oracle’s
documentation to state that it rejects retirement when the checkpoint is exactly
at gcTime, matching the current behavior of advanceModel and check. Clarify that
the oracle permits retirement only after that deadline unless the comparison is
intentionally changed.
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docs/contributing/oracle-coverage.md
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The law makes a Collection eligible at gcTime, and exact cleanup latency is not
promised. The model previously required the Collection not to be retired at the
checkpoint that lands exactly on the deadline. It now owes either outcome there,
owes no retirement before the deadline, and owes retirement at the first
checkpoint after it. The retirement-latency prose states the grid's limit: a
retirement one tick early (gcTime - 1 ms) lands on the exact-deadline checkpoint
and is no longer detected. No finer clock steps were added.
Evidence block
- Law: automatic GC makes a Collection eligible at gcTime with no subscriber and
no persisting transaction. Authority: BaseCollectionConfig.gcTime; the
coverage-map GC retention boundaries entry (exact wall-clock cleanup latency is
not promised); the maintainer's decision recorded by the coordinator for this
change.
- Reach: unchanged states and constructed histories. Fixed seed 20261024 reach:
see the run. Default and seeds 1..5: 3/3 green.
- RED: none on unchanged production. The change relaxes the model, and production
passes it.
- GREEN: the oracle passes 3/3 at default seeds and seeds 1..5. oracle-replay is
not rerun in this commit. Lint: pnpm lint:changed clean. tsc: no error in the
oracle file; one pre-existing vite.config.ts rootDir error.
- Mutants, each applied alone to packages/db/src/collection/lifecycle.ts and
restored: delay gcTime + 30 is violated at "step 0 advance" (still killed). Delay
gcTime + 1 SURVIVES (as before). Delay gcTime - 1 SURVIVES, a weakening: the
previous strict model killed it at "step 2 advance". This is the cost of the
allowed exact-deadline outcome, and it is recorded as a limit, not hidden.
- Limits: the grid cannot separate retirement at gcTime - 1 ms or gcTime + 1 ms
from the deadline. A finer clock grid would be needed to claim either.
Co-authored-by: Isaac <no-reply@databricks.com>
Explicit cleanup was generated only as a history's end, so no history settled,
unsubscribed from, or restarted a cleaned-up Collection. The grammar now has a
cleanup step (one side or both) at any point, with reach states
settle-after-cleanup, unsubscribe-after-cleanup, restart-after-cleanup, and
write-while-discarded. cleanup-while-persisting is now counted per side.
Law and authority: explicit cleanup discards the rows of the transactions that
persist on the Collection, and the discarded rows stay excluded after the
restart and after later recomputes; the hold itself persists (round 3 review,
oracle-reviews/pr-2258-gc-retention-round3.md: "Cleanup starts by discarding
public rows", "Explicit cleanup overrides retention"; pr-2258-gc-retention.md
records the repair of sibling-row resurrection after explicit cleanup, commit
3e4052e). Until the next subscribe a cleaned-up Collection stays cleaned up
(glossary cleanup and cleanup start). A direct subscription survives cleanup, so
the subscriber count is not reset (glossary cleanup). The delay after a
settlement on a cleaned-up Collection is a stated limit, not a rule.
Evidence block
- Law: as above.
- Reach: the constructed history "write after restart while a discarded row
persists" enters write-while-discarded in every campaign. Other constructed
histories enter the new states listed above. Reach counts appear in the run.
- RED (command: in packages/db, npx vitest run --coverage.enabled=false
tests/collection-gc-transaction-oracle.property.test.ts, on the parent
production): FAILS at fixed seed 20261024, path 9:8:19:11:11, the constructed
history. Shrunk counterexample: [insert b, cleanup b, subscribe b, insert b,
settle complete]. Violation at "step 3 insert": the model owes b keys [2],
production shows [1, 2]. Random seeds -277388568 and -1002447957 also fail with
the same resurrection. The fix follows in the next commit.
- GREEN: not applicable to this commit, since production is unchanged.
- Mutant Ma (cleanup resets the subscriber count): the parent oracle passed it
(3/3). With this extension, Ma is NOT a clean RED or GREEN yet, because the
unmutated production already fails the resurrection path. The earlier
status-only scratch campaign killed Ma, but that is not committed evidence.
Ma is re-measured after the production fix.
- Limits: writes into a cleaned-up Collection are not generated, and this oracle
claims no owner for that restart. The delay after a settlement on a cleaned-up
Collection is not observable and is stated as a limit.
Co-authored-by: Isaac <no-reply@databricks.com>
An explicit cleanup() discards the optimistic rows of the transactions that are
persisting on a Collection. Those transactions keep their hold until they
settle. The overlay skipped them only while the Collection was cleaning up or
cleaned up, so once it restarted, the next write re-derived the discarded rows
and they reappeared. The repair from 3e4052e covered only the settlement path.
The fix records each transaction that cleanup discards in state.ts, and the
overlay skips exactly those transactions, even after the restart. The
cleaned-up status clause of the guard is removed. The cleaning-window skip stays.
Law and authority: as in the previous commit (round 3 review: "Cleanup starts by
discarding public rows", "Explicit cleanup overrides retention"; the
pr-2258-gc-retention review record of sibling-row resurrection after explicit
cleanup, commit 3e4052e).
Evidence block
- Law: explicit cleanup discards the rows of transactions persisting on the
Collection, and they stay excluded after restart and later recomputes.
- Reach: the constructed history "write after restart while a discarded row
persists" enters write-while-discarded in every campaign (see the previous
commit).
- RED: on the parent production (the previous commit), the oracle fails at fixed
seed 20261024, path 9:8:19:11:11 (model owes b keys [2], production [1, 2]).
Random seeds -277388568 and -1002447957 fail too. Hostile variant: the original
cleaned-up-only guard is the parent code, so it has the same RED. A fix that
guards only while cleaned up fails the same way.
- GREEN: packages/db, collection-gc-transaction-oracle.property.test.ts passes
3/3 at default seeds and seeds 1..5. Neighbouring GC and optimistic oracles
pass (7 files, 369 tests). The full packages/db suite passes at 2 workers (396
files, 52,079 tests).
- Mutant Ma (cleanup resets the subscriber count), applied to changes.ts on the
fixed production: RED, violated at "step 5 advance" in the drain-fail history
subscribe, cleanup, subscribe, unsubscribe. Unmutated: GREEN. The parent oracle
passed Ma, so this is a new kill.
- Code weight: the full minified packages/db build, gzip -9 of all dist/esm
files, changes from 147,434 to 147,465 bytes (+31). Brotli was not measured.
pnpm size:compare could not run, because it installs dependencies in its
baseline worktree and installs are not permitted here.
- Full suite: passes at 2 workers on the final code (396 files, 52,079 tests).
- Limits: the cleaning-window skip is kept, so a write during an in-progress
cleanup still does not overlay. Writes into a cleaned-up Collection remain a
stated limit.
Co-authored-by: Isaac <no-reply@databricks.com>
The retirement-latency bound needs a checkpoint one millisecond before a
deadline, and the 20/60/120 ms grid had none. The clock grid now includes 1 ms,
and MAX_STEPS rises to 24, because a checkpoint at gcTime - 1 ms needs 21 clock
steps from a deadline set at time 0. A constructed history (60, 20, then nineteen
1 ms steps) enters the new state one-millisecond-before-deadline.
The model owes no retirement before gcTime. From gcTime up to
RETIREMENT_LATENCY_MS (20 ms) after it, either outcome is allowed. From that bound
on, retirement is owed. The 20 ms bound matches the previous grid's next step,
so the owed behavior at 20 ms steps is unchanged. It is a checker bound, not a
product promise.
Evidence block
- Law: automatic GC makes a Collection eligible at gcTime, and exact cleanup
latency is not promised. Authority: BaseCollectionConfig.gcTime; the
coverage-map GC retention boundaries entry; decision (1) of this series.
- Reach: new state one-millisecond-before-deadline, entered by its constructed
history in every campaign. Fixed seed 20261024 reaches it 4 times; the random
seed in the run reaches it 3 times, and the generated 1 ms steps add more.
- RED on the parent production (9a57551): the gcTime - 1 ms timer mutant
SURVIVES, because its retirement is not observed at the 99 ms checkpoint in
this harness, so it is indistinguishable from an exact-deadline retirement.
The gcTime - 2 ms timer mutant FAILS at a 1 ms checkpoint below gcTime.
- GREEN: the oracle passes 3/3 at default seeds and seeds 1..5, with the new
reach. The neighbouring GC oracles and oracle-replay pass (4 files, 131 tests).
pnpm lint:changed is clean. tsc has no error in the oracle file; one
pre-existing vite.config.ts rootDir error remains.
- Mutants: gcTime + 1 ms survives (allowed, latency not promised). gcTime + 30 ms
fails at "step 0 advance". Ma (cleanup resets the subscriber count) fails on the
fixed production. The original defect (the cleaned-up-only guard, restored in
state.ts) fails at "step 3 insert".
- Limits: the early-retirement check is limited to 2 ms early, and the 1 ms timer
mutant is not separated from exact retirement. The latency bound is a checker
bound. Writes into a cleaned-up Collection remain a stated limit.
Co-authored-by: Isaac <no-reply@databricks.com>
KyleAMathews
changed the title
test(db): give the GC transaction oracle constructed histories for every reach state
fix(db): keep rows discarded by cleanup cleared after a restart; build GC oracle reach from constructed histories
Nov 9, 2026
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KyleAMathews
changed the title
🎯 Changes
Fixed: a row discarded by an explicit cleanup came back after a restart.
collection.cleanup()discards the rows of transactions that are still persisting. Earlier decisions (thepr-2258-gc-retentionreviews) say that those rows stay cleared. The fix in #2258 skipped a discarded transaction's rows only while the Collection was cleaning up or cleaned up. After a subscribe restarted the Collection, the next write recomputed the optimistic state and showed the discarded row again. Nowstate.cleanup()records the transactions it discards, and the optimistic overlay skips exactly those transactions. Transactions that start after the cleanup show their rows as before.docs/contributing/oracle-reviews/pr-2258-gc-retention-round3.md("Cleanup starts by discarding public rows"; "restart after GC owes no discarded-draft restoration") and the fix(db): keep a collection from garbage collection while its transaction persists #2258 repair of row resurrection after explicit cleanup.[2]and production shows[1, 2]. Random seeds -277388568 and -1002447957 fail the same way.packages/dbsuite passes (396 files, 52,079 tests).packages/dbbuild.pnpm size:comparecould not run here, because it installs dependencies in its baseline worktree.Oracle extensions that found it: the oracle now generates an explicit
cleanupstep in the middle of a history. It declares reach states for a settlement, an unsubscribe, a restart, and a write after a cleanup. A Collection's settlement-restart functions intransactions.tsare owned. A 1 ms clock step checks one millisecond before a deadline. A transition-table version of this model (a prototype, not in this PR) showed that the old grammar never fired the transitions after a cleanup.The garbage-collection transaction oracle (
collection-gc-transaction-oracle.property.test.ts) now runs onoracleProperty, and its reach comes from constructed histories. Before this change, it ran a rawfc.assertcampaign with a reach floor of 1, so its reach depended on the seed. At seed -977831430, its random campaign never enteredsettled-while-subscribedand failed on reach alone. No law failed.The law, its authority, the model's rules, the production driver's operations, and the comparison do not change. The property id, the fixed seed 20261024, and the run budget of 100 also stay the same.
resolve(history)turns each history into a legal plan with handler ids and drain steps. The model computes the expected snapshot after each action from that plan, and the driver only records each Collection's status and rows.An earlier commit on this branch added literal fixed histories instead. A review showed that they were not declared to the reach. The maintainer then said that reach must keep randomness, which is what constructed histories give.
🔬 Oracle Coverage
gcTimewith no subscriber and no persisting transaction. Authority:BaseCollectionConfig.gcTimeand the persisting-transaction hold inlifecycle.ts, as the oracle's prose states.TANSTACK_DB_ORACLE_SEED=-977831430 pnpm --filter @tanstack/db exec vitest run tests/collection-gc-transaction-oracle.property.test.tson main fails withsettled-while-subscribed (0).oracle-replay.test.tspasses 116 of 116 tests.pnpm lint:changedand the run-budget check report nothing.constructed history "settled while subscribed" did not enter settled-while-subscribed.canGarbageCollectignores subscribers, both generated campaigns fail on the retirement law.gcTimeis a violation. FromgcTimeto 20 ms after it, either outcome is allowed, because exact cleanup latency is not promised; after that, retirement is owed. A mutant that retires 2 ms early fails. A mutant that retires 1 ms early survives, because this harness cannot tell it apart from a retirement exactly atgcTime, which the law allows.This was a follow-up from #2378, which found the reach failure during a full db run.
✅ Checklist
pnpm test. I ran the changed oracle at the default and recorded seeds, both mutants,oracle-replay.test.ts, andpnpm lint:changed. A code review and a simplification pass ran on an earlier version of this branch.🚀 Release Impact
@tanstack/db: patch).This pull request and its description were written by Isaac.