fix(store): use PASSIVE checkpoint to avoid file-shrink under concurrent readers#316
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edwardmhughes wants to merge 1 commit intoDeusData:mainfrom
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fix(store): use PASSIVE checkpoint to avoid file-shrink under concurrent readers#316edwardmhughes wants to merge 1 commit intoDeusData:mainfrom
edwardmhughes wants to merge 1 commit intoDeusData:mainfrom
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…ent readers cbm_store_checkpoint() invoked SQLITE_CHECKPOINT_TRUNCATE, the most aggressive mode. When two cbm-mcp processes share a cache dir, one process's TRUNCATE can shrink files while another has them mmap'd, raising SIGBUS on macOS. PASSIVE never blocks readers and never ftruncate()s either file; SQLite still autocheckpoints in PASSIVE mode at 1000-page boundaries, so reclamation is unaffected for single-process users. Recommended by SQLite docs for shared databases: https://www.sqlite.org/pragma.html#pragma_wal_checkpoint
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Summary
cbm_store_checkpoint()usedSQLITE_CHECKPOINT_TRUNCATE— the most aggressive checkpoint mode. On success it callsftruncate(fd, 0)on the WAL file. When twocodebase-memory-mcpprocesses share a cache dir, the truncation can shrink files while a sibling has the DB mmap'd through SQLite, raisingSIGBUSon macOS (cluster_pagein past EOF).Switching to
SQLITE_CHECKPOINT_PASSIVEcloses this truncation path:ftruncate()on either fileFrom the SQLite docs on wal_checkpoint:
Changes
src/store/store.c:SQLITE_CHECKPOINT_TRUNCATE→SQLITE_CHECKPOINT_PASSIVEwith explanatory commenttests/test_store_checkpoint.c(new): Verifies WAL is not truncated to zero bytes aftercbm_store_checkpoint()— this test would fail on the old TRUNCATE mode under the right timingMakefile.cbm+tests/test_main.c: Wire new test suiteFixes #314
Related: #277 (orphan-process WAL pin on Windows)