✨ Add Reranker model

generic_rag/app.py

@@ -8,7 +8,13 @@ import chainlit as cl
 from chainlit.cli import run_chainlit
 from langchain_chroma import Chroma
 
-from generic_rag.backend.models import ChatBackend, EmbeddingBackend, get_chat_model, get_embedding_model
+from generic_rag.backend.models import (
+    ChatBackend,
+    EmbeddingBackend,
+    get_chat_model,
+    get_embedding_model,
+    get_compression_model,
+)
 from generic_rag.graphs.cond_ret_gen import CondRetGenLangGraph
 from generic_rag.graphs.ret_gen import RetGenLangGraph
 from generic_rag.parsers.parser import add_pdf_files, add_urls
@@ -103,6 +109,9 @@ else:
         chat_model=get_chat_model(args.chat_backend),
         embedding_model=get_embedding_model(args.emb_backend),
         system_prompt=system_prompt,
+        compression_model=get_compression_model(
+            "BAAI/bge-reranker-base", vector_store
+        ),  # TODO: implement in config parser
     )
 
 
@@ -129,7 +138,9 @@ async def add_sources(chainlit_response: cl.Message, pdf_sources: dict, web_sour
         for source, page_numbers in pdf_sources.items():
             filename = Path(source).name
             await chainlit_response.stream_token(f"- {filename} on page(s): {sorted(page_numbers)}\n")
-            chainlit_response.elements.append(cl.Pdf(name=filename, display="side", path=source, page=sorted(page_numbers)[0]))
+            chainlit_response.elements.append(
+                cl.Pdf(name=filename, display="side", path=source, page=sorted(page_numbers)[0])
+            )
 
     if len(web_sources) > 0:
         await chainlit_response.stream_token("\n\nThe following web sources were consulted:\n")

generic_rag/backend/models.py

@@ -1,12 +1,17 @@
 import os
 from enum import Enum
 
+from langchain_chroma import Chroma
 from langchain.chat_models import init_chat_model
 from langchain_aws import BedrockEmbeddings
 from langchain_core.embeddings import Embeddings
 from langchain_core.language_models.chat_models import BaseChatModel
+from langchain_core.retrievers import BaseRetriever
 from langchain_google_vertexai import VertexAIEmbeddings
 from langchain_huggingface import HuggingFaceEmbeddings
+from langchain.retrievers import ContextualCompressionRetriever
+from langchain.retrievers.document_compressors import CrossEncoderReranker
+from langchain_community.cross_encoders import HuggingFaceCrossEncoder
 from langchain_ollama import ChatOllama, OllamaEmbeddings
 from langchain_openai import AzureChatOpenAI, AzureOpenAIEmbeddings, OpenAIEmbeddings
 
@@ -83,3 +88,10 @@ def get_embedding_model(backend_type: EmbeddingBackend) -> Embeddings:
         return HuggingFaceEmbeddings(model_name=os.environ["HUGGINGFACE_EMB_MODEL"])
 
     raise ValueError(f"Unknown backend type: {backend_type}")
+
+
+def get_compression_model(model_name: str, vector_store: Chroma) -> BaseRetriever:
+    base_retriever = vector_store.as_retriever(search_kwargs={"k": 20})
+    rerank_model = HuggingFaceCrossEncoder(model_name=model_name)
+    compressor = CrossEncoderReranker(model=rerank_model, top_n=4)
+    return ContextualCompressionRetriever(base_compressor=compressor, base_retriever=base_retriever)

generic_rag/graphs/ret_gen.py

@@ -8,6 +8,7 @@ from langchain_core.embeddings import Embeddings
 from langchain_core.language_models.chat_models import BaseChatModel
 from langchain_core.messages import BaseMessage, SystemMessage
 from langchain_core.runnables.config import RunnableConfig
+from langchain_core.retrievers import BaseRetriever
 from langgraph.checkpoint.memory import MemorySaver
 from langgraph.graph import END, START, StateGraph
 from typing_extensions import List, TypedDict
@@ -23,12 +24,18 @@ class State(TypedDict):
 
 class RetGenLangGraph:
     def __init__(
-        self, vector_store: Chroma, chat_model: BaseChatModel, embedding_model: Embeddings, system_prompt: str
+        self,
+        vector_store: Chroma,
+        chat_model: BaseChatModel,
+        embedding_model: Embeddings,
+        system_prompt: str,
+        compression_model: BaseRetriever | None = None,
     ):
         self.vector_store = vector_store
         self.chat_model = chat_model
         self.embedding_model = embedding_model
         self.system_prompt = system_prompt
+        self.compression_model = compression_model
 
         memory = MemorySaver()
         graph_builder = StateGraph(State).add_sequence([self._retrieve, self._generate])
@@ -45,7 +52,10 @@ class RetGenLangGraph:
 
     def _retrieve(self, state: State) -> dict[str, list]:
         logger.debug(f"querying VS for: {state["question"]}")
-        self.last_retrieved_docs = self.vector_store.similarity_search(state["question"])
+        if self.compression_model:
+            self.last_retrieved_docs = self.compression_model.invoke(state["question"])
+        else:
+            self.last_retrieved_docs = self.vector_store.similarity_search(state["question"])
         return {"context": self.last_retrieved_docs}
 
     def _generate(self, state: State) -> dict[str, list]: