Fix for issue #46. All credits to @efraintorlo

query_data.py

@@ -1,7 +1,7 @@
 """Create a ChatVectorDBChain for question/answering."""
 from langchain.callbacks.base import AsyncCallbackManager
 from langchain.callbacks.tracers import LangChainTracer
-from langchain.chains import ChatVectorDBChain
+from langchain.chains import ConversationalRetrievalChain
 from langchain.chains.chat_vector_db.prompts import (CONDENSE_QUESTION_PROMPT,
                                                      QA_PROMPT)
 from langchain.chains.llm import LLMChain
@@ -12,9 +12,9 @@
 
 def get_chain(
     vectorstore: VectorStore, question_handler, stream_handler, tracing: bool = False
-) -> ChatVectorDBChain:
-    """Create a ChatVectorDBChain for question/answering."""
-    # Construct a ChatVectorDBChain with a streaming llm for combine docs
+) -> ConversationalRetrievalChain:
+    """Create a ConversationalRetrievalChain for question/answering."""
+    # Construct a ConversationalRetrievalChain with a streaming llm for combine docs
     # and a separate, non-streaming llm for question generation
     manager = AsyncCallbackManager([])
     question_manager = AsyncCallbackManager([question_handler])
@@ -45,8 +45,8 @@ def get_chain(
         streaming_llm, chain_type="stuff", prompt=QA_PROMPT, callback_manager=manager
     )
 
-    qa = ChatVectorDBChain(
-        vectorstore=vectorstore,
+    qa = ConversationalRetrievalChain(
+        retriever=vectorstore.as_retriever(),
         combine_docs_chain=doc_chain,
         question_generator=question_generator,
         callback_manager=manager,

requirements.txt

@@ -4,10 +4,11 @@ black
 isort
 websockets
 pydantic
-langchain
+langchain==0.0.152
 uvicorn
 jinja2
 faiss-cpu
 bs4
 unstructured
 libmagic
+tiktoken