The phantom-producer detector (#795) was doing UPDATE + SELECT in two
roundtrips — first incrementing consecutive_empty_runs, then re-
reading to check the stale threshold. Switch to UPDATE ... RETURNING
so the post-increment value comes back in one query.
Called once per schedule per cron tick. At 100 tenants × dozens of
schedules per tenant, the halved DB traffic on the empty-response
path is measurable, not just cosmetic.
Also now properly logs if the bump itself fails (previously it silent-
swallowed the ExecContext error and still ran the SELECT, which would
confuse debugging).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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