The merger's neighbour query matched "end_id = ? OR start_id = ?", which
no index serves: it read every range of the group per file, 5.5 s a
round and most of Postgres's time in an end-to-end run. Now the range
holding the article before and after, by (group_id, start_id): 0.08 ms.
The prefetcher's leased and started ranges (every 2 s) get partial
indexes: 15-25 ms -> <0.1 ms with 145k planned ranges.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
