-- Track which interstate carriers have been sent the IFTA quarterly-return
-- reminder this cycle, so the daily IFTA cron never double-sends within a quarter.
-- The IFTA campaign builder resets this column at the start of each new quarter's
-- reminder window (see build_ifta_quarterly_campaign.py).

ALTER TABLE fmcsa_carriers
  ADD COLUMN IF NOT EXISTS ifta_reminded_at TIMESTAMPTZ;

CREATE INDEX CONCURRENTLY IF NOT EXISTS idx_fmcsa_carriers_ifta_reminded
  ON fmcsa_carriers (ifta_reminded_at)
  WHERE ifta_reminded_at IS NULL;