message: Using sort unstable by key.
diff: @@ -98,7 +98,7 @@ impl MultiFieldPostingsWriter {
  .iter()
  .map(|(term_bytes, addr, bucket_id)| (term_bytes, addr, bucket_id as UnorderedTermId))
  .collect();
  - term_offsets.sort_by_key(|&(k, _, _)| k);
  + term_offsets.sort_unstable_by_key(|&(k, _, _)| k);
  let mut offsets: Vec<(Field, usize)> = vec![];
  let term_offsets_it = term_offsets
  