Classic IR

Find code and text fast, locally. Proven stack: BM25 via FTS5, dense-slot interface, reciprocal-rank fusion, RM3 pseudo-relevance expansion. Index your files, search with ranked BM25, expand queries, fuse rankings.

Commands (ir.py, stdlib + sqlite3 FTS5)

python ir.py index DIR --db corpus.db     # index .md/.txt files
python ir.py search DB "query" [--k 100]  # BM25 ranked JSON
python ir.py expand DB "query" [--k 5]    # RM3 candidate terms from top-k
python ir.py fuse A.json B.json [--k 60]  # RRF fusion of two rankings

Rules

• First-pass is BM25 always (zero-shot robust, cheap, exact-match).
• Dense/LLM rerank only over top-100 — never full-corpus.
• RM3 expansion is opt-in per query (drift risk); log expansions.

Worked example

python ir.py index ./notes --db notes.db        # 2 files indexed
python ir.py search notes.db "BM25 saturation"  # [{"path":"a.md","rank":1}]
python ir.py expand notes.db "BM25"             # [{"term":"rank","df_topk":2}]

Limits: lexical only (no semantics); Python ≥3.8 + FTS5; stdlib only, no network, no secrets.