perf: batch tombstone writes (C4) + structured batch DELETE (B3) - #369
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September 3, 2026 20:18
… 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.
- IStorage.TombstoneRecords (default loops TombstoneRecord); Storage batches the in-place negative-prefix markers over one cached read handle and evicts each affected page-cache page once instead of once per row. - ApplyBufferedTombstones (commit path) and Table.TombstoneDeletedPositions (direct non-transactional deletes) route through the batch API; offsets that are not physical records (EOF/already-marked) are skipped safely.
…parse (B3) - TryParseDeleteForBatch now also returns the canonical WHERE column + raw literal; ExecuteBatchSQL groups (where, column, literal) instead of plain WHERE strings. - Table.DeleteMultipleKeys mirrors DeleteMultiple (contiguous-FW gate -> PK fast path -> hash fast path -> generic fallback) but resolves keys directly from the pre-parsed column/literal; the 'col = literal' string and the second TryParseSimpleWhereClause pass are built only when a generic fallback actually runs. - Non-canonical statements keep the string path (mixed tables rebuild on the rare path).
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This was referenced Sep 3, 2026
MPCoreDeveloper
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September 3, 2026 19:35
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Stack
perf/commit-time-tombstones(PR perf: apply DELETE tombstones at COMMIT for transactional deletes (no flush rewrite) #368) ← baseperf/tombstone-delete(PR perf: durable Columnar DELETE in-place via tombstone markers (no flush rewrite) #367) ← master.Inhoud (twee commits)
C4 —
a862757abatch-tombstones met evict-dedupIStorage.TombstoneRecords(path, offsets)(default = per-offsetTombstoneRecord); Storage-implementatie schrijft de negatieve-prefix-markers over één gecachete read-handle en evict per page één keer i.p.v. per rij.ApplyBufferedTombstones) als de directe non-transactionele deletes (Table.TombstoneDeletedPositions) lopen via de batch-API; offsets die geen fysiek record zijn (EOF / al gemarkeerd) worden veilig overgeslagen.B3 —
78d21ea1structured batch-DELETE (geen dubbele parse)TryParseDeleteForBatchretourneert ook de canonieke WHERE-column + ruwe literal;ExecuteBatchSQLgroepeert(where, column, literal).Table.DeleteMultipleKeysspiegelDeleteMultiple(contiguous-FW-gate → PK-fast-path → hash-fast-path → generieke fallback) maar resolve keys direct uit de voorgeparste waarden; decol = literal-string en de tweedeTryParseSimpleWhereClauseworden alleen gebouwd als een generieke fallback écht nodig is.Meting (Release, 10K deletes op ~100K rijen; median van 3 runs)
--pklegacy / fixed-widthConclusie: functioneel neutraal binnen run-ruis (±10%). De wijzigingen zijn veilig (full suite groen) en verminderen allocaties (B3) en page-cache-evicts + handle-gebruik (C4) — pas bij grotere tabellen/allocatie-gevoelige workloads zichtbaar. De volgende echte hefboom blijft B1 (key-only deletes zonder per-rij
engine.Read+ volledige rij-deserialisatie).Validatie
SharpCoreDB.Testsfull suite (Debug) + Release/CI-filter op alle vier de suites (incl. VectorSearch/EFCore/Linq2DB): EXIT=0.