fix(memory): make save_compression_guidelines version bump atomic#1810
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fix(memory): make save_compression_guidelines version bump atomic#1810
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) Replace the read-then-write version increment with a single atomic INSERT ... SELECT COALESCE(MAX(version), 0) + 1 statement. SQLite's single-writer WAL guarantee makes this safe without an explicit transaction; two concurrent callers can no longer both observe version=N and both insert version=N+1. Migration 033 adds a UNIQUE(version) constraint to the compression_guidelines table. To handle databases that already contain duplicate version rows from the original bug, the migration deduplicates by keeping the row with the highest rowid per version before applying the constraint. Tests added: - unique_constraint_prevents_duplicate_version: raw INSERT of a duplicate version must fail with a UNIQUE constraint error - concurrent_saves_produce_unique_versions: 8 concurrent writers on a shared file-backed WAL database all produce distinct version numbers Closes #1799
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Summary
save_compression_guidelineswith a single atomicINSERT ... SELECT COALESCE(MAX(version), 0) + 1statementUNIQUE(version)constraint oncompression_guidelines, with row-level deduplication for pre-existing corrupt dataunique_constraint_prevents_duplicate_versionandconcurrent_saves_produce_unique_versions(file-backed WAL DB, 8 concurrent writers)Closes #1799
Test plan
cargo nextest run --config-file .github/nextest.toml -p zeph-memory --lib -E 'test(compression_guidelines)'— 10 passedcargo nextest run --config-file .github/nextest.toml --workspace --features full --lib --bins— 5789 passedcargo clippy --workspace --features full -- -D warnings— cleancargo +nightly fmt --check— clean