Function purgeOldEvents

telemetry-worker/src/rollup.ts:239–251

(env: Env, cutoff: string)

 * keyset subquery stays a cheap index range scan on (day, event).
 */
export async function purgeOldEvents(env: Env, cutoff: string): Promise<PurgeResult> {
  const del = env.DB.prepare(
    `DELETE FROM events WHERE id IN (SELECT id FROM events WHERE day < ? LIMIT ${PURGE_BATCH_ROWS})`,
  );
  let deleted = 0;
  for (let batch = 1; batch <= PURGE_MAX_BATCHES; batch++) {
    const { meta } = await del.bind(cutoff).run();
    const removed = meta?.changes ?? 0;
    deleted += removed;
    if (removed < PURGE_BATCH_ROWS) return { cutoff, deleted, batches: batch, capped: false };
  }
  return { cutoff, deleted, batches: PURGE_MAX_BATCHES, capped: true };
}

/**
 * The cron body: roll up the completed day and the two before it, then purge.