# Retrieval Patterns

> Retrieval Patterns SKILL

- Skill: `majiayu000/retrieval-patterns-2` (Agent Skill)
- Install (CLI): `npx skillmds@latest add majiayu000/retrieval-patterns-2`
- Raw SKILL.md: https://api.skillmd.com/api/skills/majiayu000/retrieval-patterns-2/raw
- Safety review: pending (external: skill-scanner PASS, skillspector PASS)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Author: majiayu000 (https://skillmd.com/u/majiayu000)
- Updated: 2026-09-22
- Page: https://skillmd.com/skills/majiayu000/retrieval-patterns-2

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# Retrieval Patterns SKILL

## 1. Hybrid Search (BM25 + Semantic)

```python
from langchain.retrievers import EnsembleRetriever

ensemble = EnsembleRetriever(
    retrievers=[bm25_retriever, semantic_retriever],
    weights=[0.5, 0.5]
)
```

## 2. MMR (Maximal Marginal Relevance)

```python
retriever = vector_store.as_retriever(
    search_type="mmr",
    search_kwargs={"k": 5, "lambda_mult": 0.5}
)
```

## 3. Cross-Encoder Reranking

```python
from langchain.retrievers.document_compressors import CrossEncoderReranker

compressor = CrossEncoderReranker(
    model_name="cross-encoder/ms-marco-MiniLM-L-6-v2"
)
```