The chunks FTS index is created once when the table is created, over zero
rows, and nothing folds later rows into it but an optimize. build_databases
bypasses populate_db, and with it the closing vacuum, so every database it
built had an index covering nothing.
Full-text search then returns near-arbitrary rows while still returning
results, so nothing looks wrong: measured FTS recall@5 of 0.0000 across 208
queries on a 40k pool, with hybrid losing 9.9pp to pure vector because the
dead branch still consumed half the fused slots.
Reachable outside the eval too, on any storage.auto_vacuum: false, which
every reference config sets. Reproduced through create_document alone:
five documents, five chunks, zero indexed rows.
Claude-Session: https://claude.ai/code/session_01WhudUtZm6qqiuv8Y1sbwSc
Hybrid search inside one database fuses its own vector and FTS rankings
with lancedb's RRFReranker over exactly the requested limit, and both
branch queries derive from the same inner query, so there is no
branch-depth knob. Below roughly 50 candidates the two rankings stop
overlapping, nothing sums, and the fusion degenerates: measured recall@5
on a single database was 0.000 at fetch 5, 10 and 20, then 0.267 at 50 and
0.350 at 100.
A dataset's retrieval_limit therefore fixes which regime it measures, and
comparing regimes would otherwise need one dataset per depth.
Claude-Session: https://claude.ai/code/session_01WhudUtZm6qqiuv8Y1sbwSc
Measures whether cross-database fusion reaches what a query needs, scored
on retrieval alone so no model or judge sits between the fusion and the
number.
The corpus is MTRAG ClapNQ partitioned by article title, whole titles to a
collection, so an article's passages never split and a query's gold stays
concentrated in one collection, which is the condition a per-collection
depth quota punishes. collection_of keys on sha256 rather than hash(),
which is salted per process: the partition is never stored, and scoring
recomputes it in a different process than the one that ingested.
The 148 titles holding a gold passage carry 10,723 passages between them,
so a budget near that floor leaves no cross-topic distractors and inflates
recall. The default is 40,000 and the build reports the gold/distractor
split, warning when there are none.
build_databases opens each collection by configured name with a scope of
one, since populate_db writes to a single database. The operator entry
point emits the config for the partition it just built, so a config cannot
search a differently-partitioned build.
Claude-Session: https://claude.ai/code/session_01WhudUtZm6qqiuv8Y1sbwSc
