perf(delete): batch commit-time tombstone marker writes per storage page (C5) - #377
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…age (C5) ApplyBufferedTombstones -> TombstoneRecords still issued one 4-byte pwrite per deleted row even after #373 batched the per-marker length reads. The DELETE commit phase now patches every negative-prefix marker into the in-memory whole-file snapshot first (markers may straddle page boundaries because records are not page-aligned, so patching must happen on the contiguous buffer, not on per-page copies) and then flushes each touched storage page exactly once. A flushed page differs from the on-disk bytes only in its flipped marker words, so the full-page write is byte-for-byte equivalent to the individual marker writes it replaces. Runs under the same lock as before (appendLock on the commit path / table write lock on the durable path), so rollback semantics are unchanged. Fair-PK harness (--pk, same machine as master, 2 runs each): legacy DELETE ~70K -> ~81K ops/s (+16%) fixed-width DEL ~97K -> ~141K ops/s (+45%); DELETE gap vs SQLite -> ~2.4x Full suite: 1762 tests, 0 failed.
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Samenvatting
Commit-time tombstone-marker writes worden per storage-page gebundeld (C5).
ApplyBufferedTombstones→TombstoneRecordsdeed na #373 (whole-file range-read) nog steeds één 4-byte pwrite per verwijderde rij; dat domineerde de DELETE-commit-fase op dichte batches. Nu:ArgumentOutOfRangeExceptionop straddlers, gevonden doorFixedWidthBulkDeleteTests).Veiligheid: draait onder hetzelfde lock als voorheen (
appendLockop het commit-pad / table-write-lock op het duurzame pad); elke page maximaal één write vanuit de snapshot → rollback kan nooit een half toegepaste marker zien.Metingen (fair-PK harness
--pk, zelfde machine als master, 2 runs elk)DELETE-gap vs SQLite op fixed-width daalt daarmee van ~3,0-3,3x naar ~2,4x.
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