Add embeddings & reranking via Sentence Transformers

README-zh.md

@@ -453,7 +453,7 @@ async def initialize_rag():
 
 * 如果您想使用Hugging Face模型，只需要按如下方式设置LightRAG：
 
-参见`lightrag_hf_demo.py`
+参见`lightrag_hf_demo.py`, `lightrag_sentence_transformers_demo.py`等示例代码。
 
 ```python
 # 使用Hugging Face模型初始化LightRAG
@@ -464,10 +464,9 @@ rag = LightRAG(
     # 使用Hugging Face嵌入函数
     embedding_func=EmbeddingFunc(
         embedding_dim=384,
-        func=lambda texts: hf_embed(
+        func=lambda texts: sentence_transformers_embed(
             texts,
-            tokenizer=AutoTokenizer.from_pretrained("sentence-transformers/all-MiniLM-L6-v2"),
+            model=SentenceTransformer("sentence-transformers/all-MiniLM-L6-v2")
-            embed_model=AutoModel.from_pretrained("sentence-transformers/all-MiniLM-L6-v2")
         )
     ),
 )
@@ -635,6 +634,7 @@ if __name__ == "__main__":
 * **Cohere / vLLM**: `cohere_rerank`
 * **Jina AI**: `jina_rerank`
 * **Aliyun阿里云**: `ali_rerank`
+* **Sentence Transformers**: `sentence_transformers_rerank`
 
 您可以将这些函数之一注入到LightRAG对象的`rerank_model_func`属性中。这将使LightRAG的查询功能能够使用注入的函数对检索到的文本块进行重新排序。有关详细用法，请参阅`examples/rerank_example.py`文件。
 

README.md

@@ -449,7 +449,7 @@ async def initialize_rag():
 
 * If you want to use Hugging Face models, you only need to set LightRAG as follows:
 
-See `lightrag_hf_demo.py`
+See `lightrag_hf_demo.py` & `lightrag_sentence_transformers_demo.py` for complete examples.
 
 ```python
 # Initialize LightRAG with Hugging Face model
@@ -457,13 +457,12 @@ rag = LightRAG(
     working_dir=WORKING_DIR,
     llm_model_func=hf_model_complete,  # Use Hugging Face model for text generation
     llm_model_name='meta-llama/Llama-3.1-8B-Instruct',  # Model name from Hugging Face
-    # Use Hugging Face embedding function
+    # Use Hugging Face Sentence Transformers embedding function
     embedding_func=EmbeddingFunc(
         embedding_dim=384,
-        func=lambda texts: hf_embed(
+        func=lambda texts: sentence_transformers_embed(
             texts,
-            tokenizer=AutoTokenizer.from_pretrained("sentence-transformers/all-MiniLM-L6-v2"),
+            model=SentenceTransformer("sentence-transformers/all-MiniLM-L6-v2")
-            embed_model=AutoModel.from_pretrained("sentence-transformers/all-MiniLM-L6-v2")
         )
     ),
 )
@@ -633,6 +632,7 @@ To enhance retrieval quality, documents can be re-ranked based on a more effecti
 * **Cohere / vLLM**: `cohere_rerank`
 * **Jina AI**: `jina_rerank`
 * **Aliyun**: `ali_rerank`
+* **Sentence Transformers**: `sentence_transformers_rerank`
 
 You can inject one of these functions into the `rerank_model_func` attribute of the LightRAG object. This will enable LightRAG's query function to re-order retrieved text blocks using the injected function. For detailed usage, please refer to the `examples/rerank_example.py` file.
 

examples/unofficial-sample/lightrag_sentence_transformers_demo.py

@@ -0,0 +1,75 @@
+import os
+
+from lightrag import LightRAG, QueryParam
+from lightrag.llm.hf import hf_model_complete
+from lightrag.llm.sentence_transformers import sentence_transformers_embed
+from lightrag.utils import EmbeddingFunc
+from sentence_transformers import SentenceTransformer
+
+import asyncio
+import nest_asyncio
+
+nest_asyncio.apply()
+
+WORKING_DIR = "./dickens"
+
+if not os.path.exists(WORKING_DIR):
+    os.mkdir(WORKING_DIR)
+
+
+async def initialize_rag():
+    rag = LightRAG(
+        working_dir=WORKING_DIR,
+        llm_model_func=hf_model_complete,
+        llm_model_name="meta-llama/Llama-3.1-8B-Instruct",
+        embedding_func=EmbeddingFunc(
+            embedding_dim=384,
+            max_token_size=512,
+            func=lambda texts: sentence_transformers_embed(
+                texts,
+                model=SentenceTransformer("sentence-transformers/all-MiniLM-L6-v2"),
+            ),
+        ),
+    )
+
+    await rag.initialize_storages()  # Auto-initializes pipeline_status
+    return rag
+
+
+def main():
+    rag = asyncio.run(initialize_rag())
+
+    with open("./book.txt", "r", encoding="utf-8") as f:
+        rag.insert(f.read())
+
+    # Perform naive search
+    print(
+        rag.query(
+            "What are the top themes in this story?", param=QueryParam(mode="naive")
+        )
+    )
+
+    # Perform local search
+    print(
+        rag.query(
+            "What are the top themes in this story?", param=QueryParam(mode="local")
+        )
+    )
+
+    # Perform global search
+    print(
+        rag.query(
+            "What are the top themes in this story?", param=QueryParam(mode="global")
+        )
+    )
+
+    # Perform hybrid search
+    print(
+        rag.query(
+            "What are the top themes in this story?", param=QueryParam(mode="hybrid")
+        )
+    )
+
+
+if __name__ == "__main__":
+    main()

lightrag/api/lightrag_server.py

@@ -781,6 +781,17 @@ def create_app(args):
                         base_url=host,
                         api_key=api_key,
                     )
+                elif binding == "sentence_transformers":
+                    from lightrag.llm.sentence_transformers import (
+                        sentence_transformers_embed,
+                    )
+
+                    actual_func = (
+                        sentence_transformers_embed.func
+                        if isinstance(sentence_transformers_embed, EmbeddingFunc)
+                        else sentence_transformers_embed
+                    )
+                    return await actual_func(texts, embedding_dim=embedding_dim)
                 elif binding == "gemini":
                     from lightrag.llm.gemini import gemini_embed
 
@@ -932,13 +943,19 @@ def create_app(args):
     # Configure rerank function based on args.rerank_bindingparameter
     rerank_model_func = None
     if args.rerank_binding != "null":
-        from lightrag.rerank import cohere_rerank, jina_rerank, ali_rerank
+        from lightrag.rerank import (
+            cohere_rerank,
+            jina_rerank,
+            ali_rerank,
+            sentence_transformers_rerank,
+        )
 
         # Map rerank binding to corresponding function
         rerank_functions = {
             "cohere": cohere_rerank,
             "jina": jina_rerank,
             "aliyun": ali_rerank,
+            "sentence_transformers": sentence_transformers_rerank,
         }
 
         # Select the appropriate rerank function based on binding

lightrag/llm/sentence_transformers.py

@@ -0,0 +1,26 @@
+import pipmaster as pm  # Pipmaster for dynamic library install
+
+if not pm.is_installed("sentence_transformers"):
+    pm.install("sentence_transformers")
+if not pm.is_installed("numpy"):
+    pm.install("numpy")
+
+import numpy as np
+from lightrag.utils import EmbeddingFunc
+from sentence_transformers import SentenceTransformer
+
+
+async def sentence_transformers_embed(
+    texts: list[str], model: SentenceTransformer
+) -> np.ndarray:
+    async def inner_encode(texts: list[str], model: SentenceTransformer, embedding_dim: int = 1024):
+        return model.encode(
+            texts,
+            truncate_dim=embedding_dim,
+            convert_to_numpy=True,
+            convert_to_tensor=False,
+            show_progress_bar=False,
+        )
+    
+    embedding_func = EmbeddingFunc(embedding_dim=model.get_sentence_embedding_dimension(), func=inner_encode, max_token_size=model.get_max_seq_length())
+    return await embedding_func(texts, model=model)

lightrag/rerank.py

@@ -290,6 +290,40 @@ async def ali_rerank(
     )
 
 
+async def sentence_transformers_rerank(
+    query: str,
+    documents: List[str],
+    top_n: Optional[int] = None,
+    api_key: Optional[str] = None,
+    model: str = "BAAI/bge-reranker-v2-m3",
+    base_url: Optional[str] = None,
+    extra_body: Optional[Dict[str, Any]] = None,
+) -> List[Dict[str, Any]]:
+    """
+    Rerank documents using CrossEncoder from Sentence Transformers.
+
+    Args:
+        query: The search query
+        documents: List of strings to rerank
+        top_n: Number of top results to return
+        api_key: Unused
+        model: rerank model name
+        base_url: Unused
+        extra_body: Unused
+
+    Returns:
+        List of dictionary of ["index": int, "relevance_score": float]
+    """
+    from sentence_transformers import CrossEncoder
+
+    cross_encoder = CrossEncoder(model)
+    rankings = cross_encoder.rank(query=query, documents=documents, top_k=top_n)
+    return [
+        {"index": result["corpus_id"], "relevance_score": result["score"]}
+        for result in rankings
+    ]
+
+
 """Please run this test as a module:
 python -m lightrag.rerank
 """
@@ -351,4 +385,19 @@ if __name__ == "__main__":
         except Exception as e:
             print(f"Aliyun Error: {e}")
         
+        # Test Sentence Transformers rerank
+        try:
+            print("\n=== Sentence Transformers Rerank ===")
+            result = await sentence_transformers_rerank(
+                query=query,
+                documents=docs,
+                top_n=2,
+            )
+            print("Results:")
+            for item in result:
+                print(f"Index: {item['index']}, Score: {item['relevance_score']:.4f}")
+                print(f"Document: {docs[item['index']]}")
+        except Exception as e:
+            print(f"Sentence Transformers Error: {e}")
+
     asyncio.run(main())