76afa75efe
Nine of them -- `$sum`, `$avg`, `$min`, `$max`, `$first`, `$last`, `$push`,
`$addToSet`, `$count` -- and the corpus goes 9 pass / 10 fail to 18 pass /
1 fail. The one left is the compound `_id`, which needs the expression
evaluator.
Landed before that evaluator, against the tier order the design review set
out, and the corpus is why: every one of these takes a single value per
document, a path or a constant, so nine of its ten failures turned out to be
reachable without one. `classify_expr` already produced exactly that value.
What the recording caught, which is the argument for measuring expectations
rather than writing them:
- `$avg` over a group with no numeric value is **null**, not `0`. A divisor
that counted documents rather than numbers would pass every test anybody
would think to write by hand, and be wrong on the one group that matters.
- `$min`/`$max` compare across types in canonical BSON order, so the maximum
of `30`, `7` and `"not a number"` is the string.
- `$push` skips an absent field but would push an explicit null, so "resolved
to nothing" and "resolved to null" cannot be the same value internally --
which is why the accumulators take `?bson.Value` and not `.null`.
- `$first`/`$last` follow input order, including when the value is absent:
`$last` of a missing field is null, not the last present one.
`AccState` is one struct rather than a union: the fields are small and every
site already switches on the kind, so a union would add a tag test where a
switch was going to be anyway. Its arrays are the gpa's, the values inside them
the reply arena's -- they outlive the group and travel with the documents.
`numeric_value` is the int32-or-double narrowing MongoDB reports, shared now
between the accumulators and `cmd_aggregate`'s count fast path. It was written
twice before; a divergence between them would make `countDocuments` disagree
with the pipeline it is a shortcut for.
`$avg` and `$push` came out of the Tier 0 refusal test, replaced by
`$stdDevPop` and `$mergeObjects`. The refusal is a property of what is missing
rather than of a list, and the test should read that way.
191/191 unit tests in ReleaseFast and ReleaseSafe, 83/83 fuzz, e2e 49, e2e3 16,
e2e4 17, e2e6 72, e2e7 86, crud corpus unchanged at 201/90/196.
MongoDB spec tests
PLAN D2 makes the official MongoDB JSON specification suites the gate for command semantics: it turns "maximally compatible" into a concrete list of test files rather than a judgement call. This directory holds the runner and the committed scorecard.
bash tests/spec/fetch.sh # pinned suites (~175 files, gitignored)
zig build # the runner spawns this binary
node tests/spec/run.js # run everything
node tests/spec/run.js --scorecard # ... and rewrite scorecard.txt
node tests/spec/run.js --file find.json --verbose
node tests/spec/run.js --url mongodb://127.0.0.1:27020 # use a server you started
What is pinned, and why both halves matter
- Suites:
mongodb/specifications@615e0f9, infetch.sh. - Driver:
mongodb@7.5.0, viatests/e2e/package-lock.json.
A scorecard is only comparable across milestones if both are pinned — otherwise a delta could be an upstream test change rather than an engine change. Bump either one in its own commit and re-record the scorecard in that same commit.
The suites are fetched rather than vendored: they are someone else's corpus, upstream rewrites them wholesale, and a pinned commit gives the same reproducibility without putting them in this repo's history.
Scope
source/crud/tests/unified/ — 175 files. The aggregate tests live there too
(aggregate*.json), so this one directory is PLAN M0's "crud + aggregate".
The runner implements the unified test format's Evaluating Matches algorithm as written in the spec, including the two rules that decide whether a result is a real pass:
- extra keys in the actual document are tolerated only in a root document;
- numeric types (int32 / int64 / double) compare flexibly.
Supported: client/database/collection entities, initialData,
outcome, expectError (code, codeName, contains, labels, errorResponse),
expectEvents, saveResultAsEntity, runOnRequirements gating, and the
$$type, $$exists, $$unsetOrMatches, $$matchesEntity,
$$matchesHexBytes operators.
expectEvents compares the commands the driver actually sent against the
expectation, exact in number and in order, with command and reply
matched as root documents so the driver's own additions (lsid, $db) are
allowed. It is what makes a pass mean the engine answered correctly and was
asked the right question — 354 of the 487 cases declare events, and before this
was asserted a case could send the wrong command and still be counted a pass.
Scorecards recorded before it landed are not comparable; there, pass was
an upper bound by construction.
Still unasserted within events, each reported as SKIP at the point of
assertion: cmap and sdam event types, ignoreExtraEvents, hasServiceId,
hasServerConnectionId, and maxTimeMS in an expected command — the runner
puts CSOT timeoutMS on every client, and CSOT overwrites maxTimeMS with
what is left of that budget, so the value on the wire is the harness's. That is
the only assertion this runner declines to make; one case in the corpus is
affected.
Not supported, each reported as SKIP with a reason and never as PASS: session
and bucket entities (M4 / GridFS), failPoint, client-side encryption,
testRunner operations, and any operation or matcher the runner does not know.
MFDB_DUMP_EVENTS=1 prints each case's observed command stream, which is the
fastest way to tell a wrong answer from a command the driver never sent.
Reading the scorecard
scorecard.txt records the totals, a per-file breakdown, and every
non-passing case with its reason. The distinction that matters:
- FAIL — the engine answered, and answered differently from the spec. Real
work. An operation that never answered inside
--op-timeout-ms(default 10 s, enforced by the driver itself via CSOTtimeoutMS) is also a FAIL, because "no answer" is a result. There is a second, much longer--case-timeout-msbackstop for a hang the driver cannot see; if it ever fires, treat the run with suspicion — see the trap below. - SKIP — nobody claims anything. Either the suite needs a feature whose milestone has not landed, or the runner does not implement it yet.
M0's gate (PLAN D7.6) is only that the harness exists and the baseline is
recorded. A red baseline is the expected state, so run.js exits 0 as long
as it ran; it is a measuring tool, not a pass/fail gate. Later milestones move
the numbers, and each one commits the new scorecard (PLAN D9).
A trap worth knowing about: the harness can invent failures
The first baseline attempt reported ~77 timeout FAILs that did not exist. Every
case from one point onward timed out, while a ping from a separate process
answered instantly — which read convincingly as a server-side wedge, and was
not.
The cause was in this runner. buildEntities opened MongoClients, and a case
that timed out before it returned left them unclosed; each one keeps a
connection pool and a heartbeat timer. Once enough accumulated, Node's event
loop was starved badly enough that the per-case timer fired before operations
could finish. Then every later case "failed".
Two things guard it now: per-test clients are owned by the caller and closed unconditionally, including on a partial failure; and the run ends by checking how many timers are still active, warning loudly if the answer is more than a handful.
The general rule, since it will come up again: a run with a long unbroken tail of timeouts is a harness bug until proven otherwise. Confirm it by running the first timing-out file on its own — if it passes in isolation, the failures are this runner's, not the engine's.
... but the third time it was the engine
A later attempt produced 166 timeout FAILs starting at file 70. I first blamed
machine load — a concurrent zig build test against a then-3-second budget —
and that was wrong. The evidence against it: the collapse reproduced on an
idle machine, at the same file, with a 10 s budget.
The actual cause was a leaked catalog lock in the engine, and it is worth
knowing how it hid. db-aggregate.json sends {aggregate: 1}, which names no
collection; dispatch resolved the namespace after taking the catalog lock and
bailed with a plain return, holding it shared forever. A leaked shared lock
is invisible to readers, so the server stayed perfectly responsive — an external
prober got ok 15ms right through the hang — and only the next write that had
to take the catalog exclusive to create a collection blocked. The failure
therefore surfaced one file later, on a different connection, as a client-side
timeout with nothing pointing at its cause.
Two lessons for using this runner:
-
A healthy-looking server does not exonerate the engine. Probe with the operation that is actually stuck, not with
ping. -
The driver's own command log is the fastest way in. It showed an insert sitting for exactly
socketTimeoutMSagainst an idle engine, which is what turned a week-long-looking mystery into a five-line fix:MONGODB_LOG_COMMAND=debug MONGODB_LOG_PATH=stderr \ node tests/spec/run.js --skip 68 --limit 2 2>drv.log
--skip/--limit exist for exactly this: the collapse reduced to a
reproducible two-file window, which is what made it tractable.
Still worth recording the baseline on an otherwise idle machine, and do not
tighten --op-timeout-ms to make a run finish sooner — a tight budget turns
load into apparent engine failures, which is how I misdiagnosed this once
already.