perf: apply DELETE tombstones at COMMIT for transactional deletes (no flush rewrite) - #368
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… flush rewrite) Stap-0 profiling showed batch DELETE (ExecuteBatchSQL wraps every batch in a storage transaction) was NOT using the tombstone path: the rollback-safe deferral only counted _pendingLogicalDeletes, so db.Flush() still ran the #366 full-file CompactPendingDeletes rewrite (~0.5-0.7s; DELETE stuck at ~12-16K ops/s). - IStorage.BufferTombstoneForCommit (default no-op) + Storage implementation: buffered offsets per file, applied as in-place negative-prefix markers by ApplyBufferedTombstones() inside FlushBufferedAppendsAndOverwrites() (the commit path) AFTER buffered appends are on disk; rollback discards the buffer via ClearBufferedAppends(). - DeleteRecordsCore + the contiguous FW bulk path now buffer the deleted offsets when IsInTransaction instead of incrementing _pendingLogicalDeletes, so the flush-time full-file rewrite is off the batch-DELETE path entirely. - Regression: batch DELETE survives reopen even WITHOUT an explicit Flush after ExecuteBatchSQL (commit already tombstoned the rows). Measured (same machine, Release, comparative harness DELETE 10K of ~100K rows): SQL 0.82s/12K -> 0.24s/41K ops/s, Direct 0.63s/16K -> 0.17s/58K ops/s; --pk legacy 0.16s/62K, fixed-width 0.13s/78K ops/s. Full suite EXIT=0.
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This was referenced Sep 3, 2026
MPCoreDeveloper
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September 3, 2026 19:35
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perf/tombstone-delete(PR perf: durable Columnar DELETE in-place via tombstone markers (no flush rewrite) #367 — in-place durable DELETE via tombstone markers).Waarom
Stap-0-profiling (env-gestuurde op/flush-splitsing +
Database.Flush-fasebreakdown) toonde:ExecuteBatchSQLdraait elke batch in een storage-transactie, dus batch-DELETE nam de rollback-veilige deferral (_pendingLogicalDeletes) endb.Flush()deed nog steeds de full-fileCompactPendingDeletes-rewrite (~0,5–0,7 s; DELETE ~12–16K ops/s). Tombstones werden in de benchmark dus nooit geschreven.Fix
IStorage.BufferTombstoneForCommit(default no-op) + Storage-implementatie: buffert per bestand de fysieke offsets van in-transactie-deletes.ApplyBufferedTombstones()draait inFlushBufferedAppendsAndOverwrites()(de commit-path) ná de buffered appends op schijf staan → markers in-place, O(delete), geen rewrite. Offsets van rijen die in dezelfde transactie zijn geïnsereerd én verwijderd zijn dan geldig.ClearBufferedAppends) gooit de buffer weg → rij blijft behouden.DeleteRecordsCore+ de contiguous FW-bulk-path bufferen de offsets i.p.v._pendingLogicalDeleteste verhogen → flush-compactie is volledig van het batch-DELETE-pad af.Metingen (zelfde machine, Release, 10K deletes op ~100K rijen)
--pklegacy--pkfixed-widthValidatie
BatchDelete_CommitTimeTombstones_SurviveReopenWithoutExplicitFlush— deletes overleven reopen zonder explicieteFlushnaExecuteBatchSQL.SharpCoreDB.Tests(Debug + Release/CI-filter) en de CI-suites (VectorSearch, EFCore, Linq2DB): EXIT=0.