How to Load vectorstore and store Locally and Build a retriever for RAG

[Scottie-tech]

Checked other resources

• I added a very descriptive title to this issue.
• I searched the LangChain documentation with the integrated search.
• I used the GitHub search to find a similar question and didn't find it.
• I am sure that this is a bug in LangChain rather than my code.
• The bug is not resolved by updating to the latest stable version of LangChain (or the specific integration package).

Example Code

vectorstore = FAISS.load_local(f"./faiss_index", load_embeddings(), allow_dangerous_deserialization=True)
store = LocalFileStore(root_path=f"./store") 
store = create_kv_docstore(store)

retriever = ParentDocumentRetriever(
    vectorstore=vectorstore,
    docstore=store,
    child_splitter=child_splitter,
    parent_splitter=parent_splitter,
    search_kwargs={"k": 5}
)

rag_chain_from_docs = (
        RunnablePassthrough.assign(context=(lambda x: format_docs(x["context"])))
        | prompt
        | llm
        | StrOutputParser()
)

rag_chain_with_source = RunnableParallel(
    {"context": retriever, "question": RunnablePassthrough()} #  compression_retriever
).assign(answer=rag_chain_from_docs)
llm_response = rag_chain_with_source.invoke(query)
print(llm_response )

The above is the code for me to load the local vectorstore and docstore and build a retriever. Using this code to query the query cannot find any information, and the large language model only answers based on its own abilities without receiving any chunks from the knowledge base.

Error Message and Stack Trace (if applicable)

No response

Description

The above is the code for me to load the local vectorstore and docstore and build a retriever. Using this code to query the query cannot find any information, and the large language model only answers based on its own abilities without receiving any chunks from the knowledge base.

System Info

python==3.10
langchain 0.1.16
langchain-community 0.0.34
langchain-core 0.1.46
langchain-openai 0.1.4
langchain-text-splitters 0.0.1
langchainhub 0.1.15
langdetect 1.0.9
langsmith 0.1.33