ADR-019: closed the "re-bench when 10M corpus exists" follow-up. Added
"Follow-up: 10M re-bench (2026-05-02)" section with the post-fix numbers
(search ~20ms warm / ~46ms cold, doc-fetch ~5ms post-btree). Documented
the lance-bench-bypassing-IndexMeta bug + 2-layer fix + gauntlet
(7 unit + 12 sanitize + 10 smoke probes). Reframes the strategic
question as "Lance vs Parquet+HNSW-with-spilling" since HNSW doesn't
fit RAM at 10M.
DECISIONS: added ADR-022 — drop Python sidecar from Rust hot path.
Captures the rationale (236× embed perf gap was pure overhead),
co-shipped LRU cache, dev-only Python that survives, cross-runtime
parity verification, and the operator runbook signal (ps -ef ABSENT
post-deploy).
PRD: updated AI Boundary table line + aibridge crate description to
reflect direct Ollama path (was: Python FastAPI sidecar → Ollama).
Both lines reference ADR-022 for the full rationale.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Standalone benchmark crate `crates/lance-bench` running Lance 4.0 against
our Parquet+HNSW at 100K × 768d (resumes_100k_v2) measured 8 dimensions.
Results (see docs/ADR-019-vector-storage.md for full scorecard):
Cold load: Parquet 0.17s vs Lance 0.13s (tie — not ≥2× threshold)
Disk size: 330.3 MB vs 330.4 MB (tie)
Search p50: 873us vs 2229us (Parquet 2.55× faster)
Search p95: 1413us vs 4998us (Parquet 3.54× faster)
Index build: 230s (ec=80) vs 16s (IVF_PQ) (Lance 14× faster)
Random access: 35ms (scan) vs 311us (Lance 112× faster)
Append 10K rows: full rewrite vs 0.08s/+31MB (Lance structural win)
Decision (ADR-019): hybrid, not migrate-or-reject.
- Parquet+HNSW stays primary — our HNSW at ec=80 es=30 recall=1.00 is
2.55× faster than Lance IVF_PQ at 100K in-RAM scale
- Lance joins as second backend per-profile for workloads where it wins
architecturally: random row access (RAG text fetch), append-heavy
pipelines (Phase C), hot-swap generations (Phase 16, 14× faster
builds), and indexes past the ~5M RAM ceiling
- Phase 17 ModelProfile gets vector_backend: Parquet | Lance field
- Ceiling table in PRD updated — 5M ceiling now says "switch to Lance"
instead of "migrate" since Lance runs alongside, not instead of
Isolation: lance-bench is a standalone workspace crate with its own dep
tree (Lance pulls DataFusion 52 + Arrow 57 incompatible with main stack
DataFusion 47 + Arrow 55). Kept off the critical path until API is
stable enough to promote into vectord::lance_store.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
