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Garry TanandClaude Opus 4.8
36a9fad214
The page-generation clock backed the query-cache Layer-1 bookmark via a FOR EACH STATEMENT trigger running `UPDATE page_generation_clock SET value=value+1 WHERE id=1`. That took a transaction-length RowExclusiveLock on one tuple, so every concurrent page writer serialized on the prior writer's COMMIT — sync ran at ~0.8 cores regardless of worker count. Swap to a SEQUENCE bumped by nextval() (a microsecond LWLock, never a row lock). The clock's only contract is monotonic advancement on any page INSERT/UPDATE/DELETE; last_value is non-transactional, so rolled-back or concurrent-uncommitted writers only OVER-invalidate the cache (lose a hit), never serve stale. - migration v118: CREATE SEQUENCE + load-bearing 2-arg setval (is_called= true, floor 1, seeded >= old clock and MAX(generation)) + repoint the trigger function body + DELETE query_cache so no old-clock bookmark survives the swap. v107 left immutable. - query-cache-gate.ts: 3 readers -> SELECT last_value FROM page_generation_clock_seq. - schema.sql + pglite-schema.ts (+ regenerated schema-embedded.ts) ship the sequence on fresh install; table + trigger names retained. - tests: clockValue reads last_value; mechanism proof (trigger fn uses nextval not the row UPDATE); rollback-advances-clock safety pin; real PGLite sequence round-trip (is_called gotcha); shape test requires _seq. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>