#4685 PR 1 — ProjectionUpdateBatch insert-only flush-mode plumbing#4697
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First PR in the BulkWriter (binary COPY) rebuild optimization series tracked in #4685. Foundation only -- adds the seam where subsequent PRs plug in: * PR 2 will TRUNCATE the projection table at rebuild start, so every batch that follows is naturally INSERT-only. * PR 3 will dispatch the actual BeginBinaryImport flush path when the batch reports BatchFlushMode.InsertOnly. * Continuous catch-up keeps the existing per-row UPSERT path -- it mixes inserts, updates, upserts, patches, and the classifier reports Mixed for those batches. **No behavior change in this PR.** The flush path is unchanged; only a new public read-only property exposes how the batch classifies itself. ## What ships * `Marten.Events.Daemon.Internals.BatchFlushMode` -- enum with `Mixed` (the default; current flush path applies) and `InsertOnly` (eligible for the BulkWriter path in PR 3). * `BatchFlushModeClassifier` -- pure, unit-testable transition rule. Initial state is `InsertOnly` (empty batch is trivially insert-only; the BulkWriter path is a no-op on zero rows); `WithOperation(current, role)` demotes to `Mixed` on any non-Insert and is monotonic -- once Mixed, stays Mixed for the lifetime of the batch. * `ProjectionUpdateBatch.FlushMode` -- public read-only property maintained incrementally in `applyOperation`. Subsequent PRs in the series dispatch on this signal. ## Tests `CoreTests/Events/Daemon/BatchFlushModeClassifier_pin.cs` (10 cases): * Initial state is InsertOnly * Inserts keep InsertOnly across multiple arrivals * Each of the five non-Insert roles (Update, Upsert, Patch, Deletion, Events, Other) demotes to Mixed independently * Monotonic: once Mixed, subsequent Inserts can't bring it back * Interleaved sequence: insert -> insert (still InsertOnly) -> update (Mixed) -> insert (still Mixed) DaemonTests pass 188/188 on net9.0 -- the projection rebuild + continuous catch-up paths exercise applyOperation across every operation role on every projection lifecycle, and the new property maintenance does not change any existing assertion. ## Series sketch * PR 1 (this PR): classifier + property. * PR 2: TRUNCATE step at the start of a per-(tenant, projection) rebuild. Partition-aware under UseTenantPartitionedEvents. * PR 3: BulkWriter (binary COPY) flush path that activates when FlushMode == InsertOnly. Reuses BulkInsertAsync's column binders. * PR 4: Composite-stage propagation review -- verify the Upstream cache propagation handles stage 2 reading stage 1's un-flushed COPY data. * PR 5: ScaleTesting harness validation. Phase E (#4684) measurement confirms the ≥30% wall-clock reduction target on the write-side of a 20M-event Telehealth composite rebuild. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
This was referenced Jun 10, 2026
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First PR in the BulkWriter (binary
COPY) rebuild optimization series tracked in #4685. Foundation only — no behavior change. Adds the seam where subsequent PRs plug in.Series sketch
BatchFlushModeproperty onProjectionUpdateBatch. No behavior change.TRUNCATEstep at the start of a per-(tenant, projection) rebuild. Partition-aware underUseTenantPartitionedEvents.COPY) flush path that activates whenFlushMode == InsertOnly. ReusesBulkInsertAsync's column binders.Upstreamcache propagation handles stage 2 reading stage 1's un-flushed COPY data.What ships in this PR
Marten.Events.Daemon.Internals.BatchFlushModeMixed(default; current flush path applies) andInsertOnly(eligible for the BulkWriter path in PR 3).BatchFlushModeClassifierInitial = InsertOnly(empty batch is trivially insert-only -- BulkWriter is a no-op on zero rows);WithOperation(current, role)demotes toMixedon any non-Insert role and is monotonic -- onceMixed, staysMixedfor the lifetime of the batch.ProjectionUpdateBatch.FlushModeapplyOperation. PR 3 dispatches on this signal.Tests
10 cases in
CoreTests/Events/Daemon/BatchFlushModeClassifier_pin.cs:InsertOnlyInsertkeepsInsertOnlyacross multiple arrivalsUpdate,Upsert,Patch,Deletion,Events,Other) independently demotes toMixedMixed, subsequentInserts can't bring it backInsert→Insert(stillInsertOnly) →Update(Mixed) →Insert(stillMixed)DaemonTests(rebuild + continuous catch-up exerciseapplyOperationon every role)The new property maintenance is one increment per operation arrival -- the perf footprint on the hot path is unmeasurable. The plumbing for PR 3 has somewhere to plug in without any of this PR changing observable Marten behavior.
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