LanceVectorStore gains build_scalar_index(column) and
has_scalar_index(column). Exposed as POST /vectors/lance/scalar-index/
{index}/{column}. activate_profile auto-builds the doc_id btree
alongside the IVF_PQ vector index when activating a Lance-backed
profile — operators get both indexes without extra API calls.
stats() now reports has_doc_id_index alongside has_vector_index.
Measured on resumes_100k_v2 (100K × 768d): random doc_id fetch
improved from ~5.4ms to ~3.5ms (35% faster). Btree build: 19ms,
+2.7 MB on disk. The remaining ~3ms is vector column materialization,
not index lookup — to close further would need a projection-only
fetch that skips the 768-float vector for text-only RAG retrieval.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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