DiskANN's delete repair only fixes forward edges (nodes the deleted
node pointed to). Stale reverse edges can cause deleted rowids to
appear in search results. Fix: track a 'confirmed' flag on each
search candidate, set when the full-precision vector is successfully
read during re-ranking. Only confirmed candidates are included in
output. Zero additional SQL queries — piggybacks on the existing
re-rank vector read.
Also adds delete hardening tests:
- Rescore: interleaved delete+KNN, rowid_in after deletes, full
delete+reinsert cycle
- DiskANN: delete+reinsert cycles with KNN verification, interleaved
delete+KNN
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Add rescore index type: stores full-precision float vectors in a rowid-keyed
shadow table, quantizes to int8 for fast initial scan, then rescores top
candidates with original vectors. Includes config parser, shadow table
management, insert/delete support, KNN integration, compile flag
(SQLITE_VEC_ENABLE_RESCORE), fuzz targets, and tests.
