Each scanned block deep-copied the newest witness of every note with
history to start that block's entry, although a block without shielded
outputs changes no witness, and spent or pending notes never change
theirs. A note's 100-entry list was 100 separate copies, mostly
identical.
The list now holds Arc-shared witnesses. The per-block duplicate is an
Arc::clone, and Arc::make_mut copies the newest entry only for unspent,
non-pending notes and only in blocks with at least one shielded output.
Every entry is still written in full, so the file is unchanged, and a
spend takes its own copy of the witness. A loaded wallet is not
de-duplicated, so the saving builds up over the next 100 blocks.
No output change: the saved bytes are identical; notes use less memory.
With 1000 live notes x 100 witnesses (a 70 MB file), RssAnon after 100
blocks without outputs is 18 MiB instead of 189 MiB and such a block
scans in 1.0 ms instead of 2.1-2.7 ms; when every block has an output,
the live bytes stay about the same.
The witness tests, the 1000-seed oracle and a differential run against
the unmodified backend (every witness entry and the whole saved file
after every operation; only the cleared lists and the chosen spend notes
may differ) all pass, and the measured wallet saves to the same SHA-256
as with the old build.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
DanSandClaude Opus 5.5
ba08cab95a