-- Formal platform sessions remain active until explicitly revoked. Keep the
-- historical columns for compatibility and auditability, but allow active
-- sessions to carry NULL expiration values.
ALTER TABLE sessions
  ALTER COLUMN expires_at DROP NOT NULL,
  ALTER COLUMN idle_expires_at DROP NOT NULL;

UPDATE sessions
   SET revoked_at = now()
 WHERE revoked_at IS NULL
   AND (expires_at <= now() OR idle_expires_at <= now());

UPDATE sessions
   SET expires_at = NULL,
       idle_expires_at = NULL
 WHERE revoked_at IS NULL;

CREATE INDEX IF NOT EXISTS sessions_token_active_idx
  ON sessions (token_hash)
  WHERE revoked_at IS NULL;