-- 017_pair_tokens_fk_cascade.sql — fix the self-contradictory FK on
-- pair_tokens.created_by.
--
-- Migration 006 declared:
--     created_by BIGINT NOT NULL REFERENCES users(id) ON DELETE SET NULL
-- which is impossible: ON DELETE SET NULL tries to write NULL into a NOT NULL
-- column, so deleting an admin that had ever minted a pair token would fail
-- with a not-null-violation instead of cleaning up the tokens.
--
-- Forward-safe fix: drop the old FK constraint and re-add it as ON DELETE
-- CASCADE. Deleting a user now removes the (short-lived, mostly-expired) pair
-- tokens they created, which is the sane behavior for onboarding tokens.
--
-- The constraint name from an inline column REFERENCES is auto-generated by
-- Postgres as <table>_<column>_fkey. We drop it defensively with IF EXISTS so
-- this migration is safe even if the name ever differed.

ALTER TABLE pair_tokens
    DROP CONSTRAINT IF EXISTS pair_tokens_created_by_fkey;

ALTER TABLE pair_tokens
    ADD CONSTRAINT pair_tokens_created_by_fkey
        FOREIGN KEY (created_by) REFERENCES users(id) ON DELETE CASCADE;