fix(db): prevent singleton poisoning when migrate() throws#111
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If migrate() threw (SQLITE_BUSY, partial prior run, disk error), the module-level `instance` was already assigned to the un-migrated Database handle. Every subsequent db() call returned this stale handle via the `if (instance) return instance` short-circuit, causing 'no such table' errors (e.g. kv_meta) for the rest of the process lifetime. Fix: use a local variable for the Database handle and only promote it to the module-level singleton after migrate() succeeds. If migrate() throws, `instance` remains undefined and the next db() call retries from scratch.
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May 2, 2026
## Summary - Fix "no such table: kv_meta" on DBs where the schema version is already at latest (11) but `kv_meta` is missing. Root cause: migration 7 is a multi-statement string (`ALTER TABLE knowledge ADD COLUMN embedding BLOB; CREATE TABLE IF NOT EXISTS kv_meta ...`). If the ALTER TABLE hits a duplicate-column error from a prior partial run, `database.exec()` aborts before `CREATE TABLE kv_meta` runs. - Catch duplicate-column errors in the migration loop, strip the already-applied ALTER statements, and re-exec the remaining SQL. - Add `recoverMissingObjects()` that idempotently creates `kv_meta` — runs both after fresh migrations and on already-at-latest DBs to heal existing broken databases. - Regression test: drops `kv_meta`, close/reopen DB, verifies recovery. Follows up on #111 (singleton poisoning prevention). That fix prevents the cached handle from being stale, but doesn't help DBs that are already at version 11 with the table missing — this PR heals those. All 583 tests pass.
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Summary
db()singleton poisoning: the module-levelinstancewas assigned beforemigrate()ran, so if migration threw (SQLITE_BUSY from lock contention, partial prior run with duplicate ALTER TABLE, disk error), every subsequentdb()call returned the un-migrated handle — causing "no such table: kv_meta" errors for the rest of the process lifetime.migrate()succeeds, so a failed init is retried on the next call.kv_metatable existence anddb()re-initialization afterclose().All 552 existing tests pass.