jsonb can't hold \u0000, and ON CONFLICT can't take a row twice in one
statement: either failed the whole flush, its outcomes lost and its
candidates taken until a restart. NULs are dropped from strings; the
probe_cache insert takes each message-id once.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Over unreadable >= false Postgres walked every waiting entry of the kind:
2.5 minutes a claim at 28M archive candidates, the prober idle every other
minute. Per value each min and max is one end of the ready index (56 ms).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>