Aleksey Shakhmatov
21489723a9
`nModified` counted every write, so an update that altered nothing was reported
as a modification. MongoDB counts a document as modified only if applying the
update changed it, and writes no oplog entry when it did not: `$set: {x: 11}`
on a document already holding `x: 11` is matched and not modified. The spec
suite says it plainly -- `bulkWrite` with four updateOne operations expects
matchedCount 2 and modifiedCount 1.
Decided in the engine rather than the command, because that is where the
document is already serialized: the comparison is against the bytes that would
actually be stored, and it lands before the log append, so a no-op costs no log
record, no fsync, no slab bytes and no garbage. `Engine.replace` returns
`Written.modified` or `.unchanged` and `cmd_update` counts the first.
That exposed a second difference. A replacement keeps `_id` at the front, so
replacing a document with itself was a byte-level change whenever `_id` was not
stored first -- and it usually was not: the Node driver fills a missing `_id` by
assigning the property, which in JavaScript appends it, so `insertOne({name,
age})` reaches the server as `{name, age, _id}` and we stored it that way.
MongoDB moves `_id` to the front whatever order it arrives in. Now so does
`serialize_with_id`, for every document rather than only the ones whose `_id` it
generates. Visible to clients as `_id` coming back first, as it does from
MongoDB.
spec scorecard 161 pass / 131 fail -> 163 pass / 129 fail
bulkWrite.json 8 pass / 2 fail -> 10 pass / 0 fail
e2e.js 45 checks -> 49
No spec file regressed. Mutation: delete the byte comparison in `upsert`'s
`.replace` arm -- red on the log growing, on the garbage counters moving, and on
`replace` claiming `.modified`.
End-to-end tests with the official MongoDB Node.js driver
These exercise MultiforaDB from a real driver over TCP: full CRUD, query operators, aggregation, error codes, concurrent clients, crash recovery, and the whole lifecycle including server restarts.
Setup
cd tests/e2e
npm init -y >/dev/null
npm install mongodb
Run
Most suites expect a server running on port 27020:
zig build
zig-out/bin/multiforadb --port 27020 --db /tmp/mfdb-e2e.log --ttl-sweep-secs 1 &
node tests/e2e/e2e.js # CRUD + operators + aggregate + errors (29 checks)
node tests/e2e/e2e2.js concurrent # 8 clients: 4 writers + 4 readers (2 checks)
node tests/e2e/e2e2.js crash-a # write 50 docs, then kill -9 the server
node tests/e2e/e2e2.js crash-b # restart and verify all 50 survived
node tests/e2e/e2e3.js # secondary indexes: unique/sparse/compound (16 checks)
node tests/e2e/e2e4.js # TTL indexes: expiry + rejected specs (15 checks)
e2e4.js needs the server started with --ttl-sweep-secs 1 (the default is
60 seconds); the other suites do not care about the flag.
e2e6.js is the full-lifecycle suite and is self-contained: it spawns its
own server on port 27220 with a fresh log, runs the whole feature surface,
restarts the server twice (graceful SIGTERM, then kill -9 mid-write) and
verifies everything survived:
node tests/e2e/e2e6.js # 73 checks, ~15 s, needs no running server
E2E6_PORT=27300 node tests/e2e/e2e6.js # different port if 27220 is taken
Rebuild with zig build after any change under src/ before restarting the
server: zig build test compiles the test binary only and leaves
zig-out/bin/multiforadb stale, so the suites keep running against the old
rules and report failures that the source no longer explains.
e2e2.js concurrent is safe to repeat against a running server (it drops its
collection first); crash-a/crash-b are two halves of one scenario.
Multi-GB collections: big.js
big.js is a load harness, not a pass/fail suite: it spawns a server, bulk
loads up to ~5 GB, and reports insert throughput, the compaction behavior,
server RSS, per-operation latencies, reopen (replay) time, and kill -9
durability.
node tests/e2e/big.js --quick # 268 MB smoke run
node tests/e2e/big.js --size 5g --doc-size 128k --oid --batch 200 \
--compact-threshold 2g # ~5 GB, 40k docs
Options: --size/--doc-size/--batch (k/m/g suffixes), --oid
(ObjectId _ids — see below), --index <field> (secondary index before
loading), --compact-threshold <bytes> (passed to the server),
--port, --keep (keep the db file).
Measured behavior (all documented in the top-level README):
- Build in ReleaseFast —
zig builddefaults to it; a Debug server is 10-200x slower on every path. - Insert throughput collapses under the default 16 MiB compaction
threshold: every ~16 MB of writes rewrites the whole log with one fsync
per record (O(n²) total). With
--compact-threshold 2gthe rate stays flat (hundreds of MB/s at 128 KB docs in ReleaseFast). Raise the threshold for bulk loads. findOne({_id})is O(1) only for ObjectId_ids. Integer_ids are serialization-ambiguous (int32/int64/double compare equal but hash differently), so the docs-map fast path is skipped and every lookup is a full scan. Use the driver's default ObjectId ids on big collections.- The engine holds everything in RAM: ~1-1.2x the data size at 128 KB docs (more at 16 KB docs, where per-document arena overhead dominates). A 5 GB collection needs roughly 6-7 GB of RAM.
- Reopen of a 5 GB log replays in ~10 s (ReleaseFast); every committed write survives kill -9.
Comparing against real MongoDB: compare.js + compare-run.sh
bash tests/e2e/compare-run.sh [size] [doc-size] # e.g. 1g 16k
Starts mongod (brew install mongodb-community) on :27018 and MultiforaDB
on :27019, runs the same driver workload against each (durable writes:
MultiforaDB fsyncs per command, mongod runs with j: true), measures kill -9
reopen for both, and prints a side-by-side table. compare.js alone runs
one side (see its --help-style header comment).
Iteration-to-iteration comparison: bench-run.sh + concurrent.js
bash tests/e2e/bench-run.sh [size] [doc-size] ["clients..."] # e.g. 1g 16k "1 4 8 16 32"
Runs the main suite (compare-run.sh) plus a concurrent durable-write
comparison (concurrent.js, N clients each doing sequential insertOne
with {w:1, j:true} — the group-commit path under real contention), then
writes a machine-readable, versioned report to
tests/e2e/results/bench-<timestamp>.txt and prints a diff of the
MultiforaDB numbers against the previous run (results/bench-latest.txt).
The report has [main] / [concurrency] / [meta] sections with
name<TAB>value rows; bench-run.sh 1g 16k reproduces the phase8 gate
(see results/phase8.txt).