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M2.5's gate, built before the milestone it gates -- the same order that put
`expectEvents` before the free list in M1 and Tier 0 before everything in M2.
`mongodb/specifications` has no aggregation suite, which is amendment A6's
central finding, so this milestone has to bring its own. The hazard in a corpus
we author is obvious and fatal: it can encode our own bugs as expectations and
then agree with us forever. So the split is enforced by the tooling.
`sources/*.json` holds documents and pipelines and nothing else; `record.js`
asks a real mongod 8.3.7 what each pipeline answers and writes the unified-
format file from the reply. Inputs authored, expectations measured -- the
discipline that corrected three assumptions in M1's session work and every
error code in M2, where the alternative would have shipped both times.
No second runner. `run.js --suite-dir` points the existing one somewhere else,
so the entity model, the matchers, the skip accounting and `expectEvents` come
for free; a second runner would drift from the first exactly where it mattered.
`--scorecard` is refused with `--suite-dir`, because `scorecard.txt` is the crud
corpus's record and the milestones are compared against it -- writing it from an
unrelated run would replace that record silently.
Errors record the code and not the message: message text is mongod's to change
between releases. Group pipelines end in a `$sort`, because group output order
is unspecified and a case depending on it would fail for the wrong reason on
either server.
The first source covers `$group`: nine accumulators including the edge cases
that decide an implementation -- `$avg` over a group whose values are not
numbers, `$min` of a field no document has, `$push` skipping a missing field,
`$first`/`$last` against input order, grouping on an array, a compound `_id`.
Where it starts, run against the M2 tip:
group-accumulators.json 9 pass 10 fail 0 skip
The nine include the four refusals M2 added, which answer with mongod's own
codes -- so the corpus already confirms that half. The ten are the milestone.
The crud corpus is unchanged at 201/90/196.
70 lines
2.7 KiB
Markdown
70 lines
2.7 KiB
Markdown
# The aggregation corpus
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`mongodb/specifications` has no aggregation suite. The thirteen
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`aggregate-*.json` files this project runs come from `crud` and test the
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aggregate *command* — cursors, read concern, the write stages, collation,
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`let`. They touch stages barely and expressions not at all: `$lookup`,
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`$unwind`, `$facet`, `$addFields` and `$replaceRoot` appear nowhere in the
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pinned corpus. That is PLAN amendment A6, and this directory is its
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consequence: M2.5 has to bring its own gate.
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## The one rule
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**Inputs are authored here; expectations are measured against a real mongod.**
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A corpus we write is a corpus that can encode our own bugs as expectations, and
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it would then agree with us forever. So `sources/*.json` holds documents and
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pipelines and nothing else, and `record.js` asks mongod 8.3.7 what each pipeline
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answers. It is the same discipline that corrected three assumptions in M1's
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session work and every error code in M2 — the alternative, in both cases, would
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have shipped.
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## Running it
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```sh
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node tests/spec/run.js --suite-dir tests/spec/aggregate
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```
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The same runner as the crud corpus, pointed elsewhere. Sharing it is the point:
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the entity model, the matchers, the skip accounting and `expectEvents` come for
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free, and a second runner would drift from the first exactly where it mattered.
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`--scorecard` is refused with `--suite-dir`: `tests/spec/scorecard.txt` is the
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crud corpus's record and the milestones are compared against it.
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## Re-recording
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```sh
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mongod --port 27099 --dbpath /tmp/mongo-corpus &
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node tests/spec/aggregate/record.js --mongod-port 27099
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```
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Writes `<name>.json` for every `sources/<name>.json`. The generated files are
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committed: they *are* the corpus, and regenerating them is how a disagreement
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with mongod gets re-measured rather than argued about.
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Two things to know when adding cases:
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- **End a `$group` pipeline with a `$sort`.** Group output order is unspecified,
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and a case that depended on it would fail for the wrong reason on either
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server.
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- **Errors record the code, not the message.** Message text is mongod's to
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change between releases; a corpus that pinned it would break for the wrong
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reason.
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Leave out any case whose answer depends on a server newer than the 4.4 this
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server reports — recording it from mongod 8.x and judging it against a 4.4
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answer measures the version gap, not the engine.
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## Where it stands
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Recorded against mongod 8.3.7, run against the M2 tip:
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```
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group-accumulators.json 9 pass 10 fail 0 skip
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```
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The nine include the four refusals M2 added, which answer with mongod's own
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codes. The ten are M2.5's work: `$avg`, `$min`, `$max`, `$first`, `$last`,
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`$push`, `$addToSet`, `$count`, and a compound `_id`.
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