has_pending() already uses the leading column of uq_jobs_live
(source_id) with the same WHERE clause. The extra index just adds
write amplification on every insert/claim/complete without improving
reads.
has_pending() scans jobs WHERE source_id=? AND status IN
('queued','claimed') on every poller sweep — without an index this
is a full table scan as the jobs table grows. Similarly,
count_succeeded_since() scans by completed_at for the dashboard's
rolling-throughput display.
Add two partial indexes:
- idx_jobs_pending_by_source: covers has_pending() lookups
- idx_jobs_succeeded_completed: covers count_succeeded_since()
Both use CREATE INDEX IF NOT EXISTS so they're idempotent on
existing databases.
