37cfa863ee
The whole corpus is green: 46 pass, 0 fail, byte-identical to mongod 8.3.7 on
every case including all 27 expressions and the compound `_id` that was the
last accumulator failure.
Expressions are *compiled once per pipeline and evaluated per document*, and
that split is the point rather than an optimisation: it keeps the property M2's
refusals bought, which is that a pipeline that cannot be answered is refused
before a single document is read instead of half way through with part of the
work already reported. `Expr` is the compiled tree, `compile_expr` reports,
`eval_expr` cannot.
Nineteen operators: `$literal`, the five arithmetic ones, seven comparisons,
`$and`/`$or`/`$not`, `$cond` in both its forms, `$ifNull` and `$switch`. Plus
the two shapes that are not operators at all -- a compound document, which is
what a `$group` `_id` usually is, and an array.
Everything the corpus recorded, and none of it guessable:
- absent and a present null are *different* internally, because `$ifNull`
treats them alike and `$push` does not. Hence `?bson.Value` throughout,
where the obvious shortcut is to fold absent into `.null` at the boundary
and lose the distinction for good.
- arithmetic over absent or null is `null` -- not an error, not zero -- and
over a string is an error, 7157723.
- `$divide` by zero is 4848401, `$switch` with no branch and no default is
40069, and both are failures only a document can produce, so `EvalError`
exists and `report_eval_error` maps it.
- two operators in one expression document is 15983 and *not* `$group`'s
40238: mongod distinguishes an expression from an accumulator there.
- truthiness is MongoDB's, so `-5` is true and `0.0` is false.
- `$mod` follows the dividend's sign, so -5 mod 4 is -1.
- `$not` takes a bare argument as readily as a one-element array.
`compile_expr` and `compile_operator` call each other, so their error set is
written out rather than inferred -- Zig cannot infer a cycle, and the failure
mode is a "dependency loop" message that says nothing about expressions.
Three cases left the Tier 0 refusal test, because a compound `_id`, `$literal`
and a `$multiply` argument all work now. What is refused should be what is
missing, so an unknown operator and a wrong operand count took their place.
191/191 unit tests in ReleaseFast and ReleaseSafe, 83/83 fuzz, e2e 49, e2e2
concurrent, e2e3 16, e2e4 17, e2e6 72, e2e7 86, crud corpus unchanged at
201/90/196.
3.7 KiB
The aggregation corpus
mongodb/specifications has no aggregation suite. The thirteen
aggregate-*.json files this project runs come from crud and test the
aggregate command — cursors, read concern, the write stages, collation,
let. They touch stages barely and expressions not at all: $lookup,
$unwind, $facet, $addFields and $replaceRoot appear nowhere in the
pinned corpus. That is PLAN amendment A6, and this directory is its
consequence: M2.5 has to bring its own gate.
The one rule
Inputs are authored here; expectations are measured against a real mongod.
A corpus we write is a corpus that can encode our own bugs as expectations, and
it would then agree with us forever. So sources/*.json holds documents and
pipelines and nothing else, and record.js asks mongod 8.3.7 what each pipeline
answers. It is the same discipline that corrected three assumptions in M1's
session work and every error code in M2 — the alternative, in both cases, would
have shipped.
Running it
node tests/spec/run.js --suite-dir tests/spec/aggregate
The same runner as the crud corpus, pointed elsewhere. Sharing it is the point:
the entity model, the matchers, the skip accounting and expectEvents come for
free, and a second runner would drift from the first exactly where it mattered.
--scorecard is refused with --suite-dir: tests/spec/scorecard.txt is the
crud corpus's record and the milestones are compared against it.
Re-recording
mongod --port 27099 --dbpath /tmp/mongo-corpus &
node tests/spec/aggregate/record.js --mongod-port 27099
Writes <name>.json for every sources/<name>.json. The generated files are
committed: they are the corpus, and regenerating them is how a disagreement
with mongod gets re-measured rather than argued about.
Two things to know when adding cases:
- End a
$grouppipeline with a$sort. Group output order is unspecified, and a case that depended on it would fail for the wrong reason on either server. - Errors record the code, not the message. Message text is mongod's to change between releases; a corpus that pinned it would break for the wrong reason.
Leave out any case whose answer depends on a server newer than the 4.4 this server reports — recording it from mongod 8.x and judging it against a 4.4 answer measures the version gap, not the engine.
Where it stands
Recorded against mongod 8.3.7. At the M2 tip it read 9 pass / 10 fail; with the accumulators in:
group-accumulators.json 19 pass 0 fail 0 skip
expressions.json 27 pass 0 fail 0 skip
group-accumulators found its first real disagreement on the way to 18:
$avg over a group with no numeric value is null, not 0, and a divisor
that counted documents rather than numbers would have passed every test
anybody would think to write by hand.
expressions.json was recorded before the evaluator was written and read
1 pass / 26 fail against it; it is green now. Expressions are exercised through
$group, because _id and the accumulator arguments are the only expression
positions that exist until $addFields and $project's computed fields land.
What recording it settled, none of which is guessable:
| mongod | |
|---|---|
$add over a missing field or null |
null, not an error and not 0 |
$add over a string |
error 7157723 |
$divide by zero |
error 4848401 |
$mod of -5 by 4 |
-1 — the dividend's sign |
$lt of a number and a string |
true — canonical type order |
$and over -5 |
truthy |
$not of a missing field |
true |
$switch with no branch and no default |
error 40069 |
| two operators in one expression document | error 15983, not $group's 40238 |
$subtract with one operand |
error 16020 |