The `dist` variable in rescore KNN quantized distance computation was
uninitialized. If the switch on quantizer_type or distance_metric
didn't match any case, the uninitialized value would propagate into
the top-k heap, potentially returning garbage results.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
sqlite3_column_blob() returns NULL for zero-length blobs or on OOM.
Several call sites in rescore KNN and DiskANN node/vector read passed
the result directly to memcpy without checking, risking NULL deref on
corrupt or empty databases. IVF already had proper NULL checks.
Adds corruption regression tests that truncate shadow table blobs and
verify the query errors cleanly instead of crashing.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Add DiskANN graph-based index: builds a Vamana graph with configurable R
(max degree) and L (search list size, separate for insert/query), supports
int8 quantization with rescore, lazy reverse-edge replacement, pre-quantized
query optimization, and insert buffer reuse. Includes shadow table management,
delete support, KNN integration, compile flag (SQLITE_VEC_ENABLE_DISKANN),
release-demo workflow, fuzz targets, and tests. Fixes rescore int8
quantization bug.
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.
