-- 107_backfill_price_per_m2.sql
-- Backfill price_per_m2 = ROUND(price_rub / total_area, 2) for rows where
-- price_rub is known but price_per_m2 was not stored by the scraper.
--
-- Context (SF FixList #16):
--   domrf_kn.py _norm_flat() now derives price_per_m2 on ingest.
--   This one-time UPDATE covers historical rows scraped before the fix.
--   For Малевич (obj_id=64701) and the wider dataset, both price_rub AND
--   price_per_m2 are NULL (DOM.RF /portal/table API does not return per-flat
--   pricing for most objects). Those rows are unaffected by this UPDATE.
--   Only rows where price_rub IS NOT NULL benefit — currently ~849 rows.
--
-- Safe to re-run: idempotent (WHERE price_per_m2 IS NULL).

BEGIN;

UPDATE domrf_kn_flats
SET price_per_m2 = ROUND((price_rub / total_area)::numeric, 2)
WHERE price_per_m2 IS NULL
  AND price_rub IS NOT NULL
  AND total_area IS NOT NULL
  AND total_area > 0;

COMMIT;