zhuyongxin
f035538531
Replace legacy MilvusServiceClient knowledge search/write with a single MilvusClientV2 hybrid store (BM25 function + dense ANN + RRFRanker). Use collection biz_hybrid and require knowledge reindex.
58 lines
2.0 KiB
Markdown
58 lines
2.0 KiB
Markdown
# Design: rag-bm25-hybrid-drop-sdk
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## Decision: single backend
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```text
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KnowledgeSearchPort
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-> MilvusHybridKnowledgeStore (MilvusClientV2 only)
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Write
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-> VectorIndexService -> MilvusHybridKnowledgeStore
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```
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No `retrieval.vector-store.mode=sdk|spring|auto` for knowledge lookup.
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## Schema (`milvus.collection`, default `biz_hybrid`)
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| field | type | notes |
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|---|---|---|
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| id | VarChar PK | chunk id |
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| content | VarChar | original chunk body returned to agent |
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| search_text | VarChar + analyzer | BM25 input (title/path/content) |
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| sparse_vector | SparseFloatVector | BM25 function output |
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| vector | FloatVector | dense embedding |
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| metadata | JSON | docId, chunkIndex, category, kb_scope, ... |
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Function: `BM25(search_text -> sparse_vector)`
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Indexes:
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- `vector`: IVF_FLAT / L2 (or COSINE if configured later)
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- `sparse_vector`: SPARSE_INVERTED_INDEX / BM25
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## Hybrid query
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```text
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AnnSearchReq(vector, FloatVec(queryEmbedding), topK, filter?)
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AnnSearchReq(sparse_vector, EmbeddedText(query), topK, filter?)
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HybridSearchReq + RRFRanker(k)
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```
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Dense-compatible score for thresholds: if entity lacks dense distance, map fused score conservatively or re-use dense-only probe. Preferred: keep dense distance when available from a parallel dense search metadata; for hybrid hits use inverse-rank placeholder only in metadata and set score from optional dense sub-hit map.
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Implementation approach for threshold stability:
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1. Run hybridSearch for ordering/identity
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2. Build map evidenceKey -> dense L2 from a concurrent dense search (same filter/topK)
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3. Attach dense score onto fused hits when present; else maxL2 (low similarity) so weak BM25-only hits don't fake PRECISE
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## Migration
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- New collection name avoids mutating legacy `biz`
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- Operators re-run knowledge init / document reindex
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- Document in acceptance
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## Drop SDK search
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- Delete SDK search methods usage from knowledge path
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- `MilvusServiceClient` bean may remain temporarily only if other non-search utilities need it; prefer migrate write/delete fully to V2 and stop creating V1 client if unused
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