-- FILTER-02 (Pitfall 1): Tender.bundesland is 100% NULL in the live DB
-- (0/1671 rows, verified) because the Phase-10 normalizer deferred
-- NUTS->Bundesland mapping to Phase 11. This migration:
--   1. Adds the CREATE INDEX for bundesland (filter performance, matches
--      schema.prisma @@index([bundesland])).
--   2. Backfills the ~1671 pre-existing rows by deriving bundesland from
--      the region column's NUTS-1 prefix (DE1..DEG -> the 16 Bundesländer),
--      mirroring geo/nuts-bundesland.ts's NUTS1_BUNDESLAND map exactly.
--
-- Idempotent: only touches rows where bundesland IS NULL AND region IS NOT
-- NULL — safe to run more than once, and never overwrites a value already
-- set by the (now-fixed) normalizer for newer ingests.
-- No user input is interpolated (T-11-05) — pure derived-field UPDATE.

-- CreateIndex
CREATE INDEX IF NOT EXISTS "Tender_bundesland_idx" ON "Tender"("bundesland");

-- Backfill
UPDATE "Tender"
SET "bundesland" = CASE upper(left("region", 3))
  WHEN 'DE1' THEN 'Baden-Württemberg'
  WHEN 'DE2' THEN 'Bayern'
  WHEN 'DE3' THEN 'Berlin'
  WHEN 'DE4' THEN 'Brandenburg'
  WHEN 'DE5' THEN 'Bremen'
  WHEN 'DE6' THEN 'Hamburg'
  WHEN 'DE7' THEN 'Hessen'
  WHEN 'DE8' THEN 'Mecklenburg-Vorpommern'
  WHEN 'DE9' THEN 'Niedersachsen'
  WHEN 'DEA' THEN 'Nordrhein-Westfalen'
  WHEN 'DEB' THEN 'Rheinland-Pfalz'
  WHEN 'DEC' THEN 'Saarland'
  WHEN 'DED' THEN 'Sachsen'
  WHEN 'DEE' THEN 'Sachsen-Anhalt'
  WHEN 'DEF' THEN 'Schleswig-Holstein'
  WHEN 'DEG' THEN 'Thüringen'
  ELSE NULL
END
WHERE "bundesland" IS NULL AND "region" IS NOT NULL;