-- version: 17
-- Backfill claims.patient_control_number = claims.id.
--
-- SP27 Task 17 fixed the 837 ingest in store.py:_claim_837_row so
-- ``Claim.patient_control_number`` is populated from
-- ``claim.claim_id`` (CLM01) instead of ``claim.subscriber.member_id``
-- (the 2010BA NM109). The reconcile matcher joins on
-- ``Claim.patient_control_number == Remittance.payer_claim_control_number``
-- and the 835 echoes CLM01 in CLP01 per X12 spec, so the wrong field
-- silently broke every auto-match in production.
--
-- For rows written BEFORE the fix, the stored value is the member_id
-- (e.g. "W953474") which never matches any remit's CLP01. This
-- migration backfills those rows by aligning
-- ``patient_control_number`` with the row's own ``id`` (= CLM01).
-- After this, every claim row's PCN is consistent with the value the
-- 837 actually sent, and any newly-ingested 835 whose CLP01 echoes
-- that CLM01 will auto-pair.
--
-- Idempotent: only touches rows where the stored PCN doesn't already
-- match the row's id, so re-running on already-fixed rows is a no-op.
--
-- Reversal safety: the migration does NOT clear matched_remittance_id,
-- so any pre-existing manual_match pairs stay intact.

UPDATE claims
SET patient_control_number = id
WHERE patient_control_number IS DISTINCT FROM id;