The final link in the chain

With the text-to-cypher chain from Chapter 1 and the vector retriever from earlier in this Chapter, you now have the components to create a chain that provides multiple ways—both vectors and nodes and relationships—to access the information in your knowledge graph.

The text_to_cypher_chain and line_retriever (the Neo4j vector retriever) variables are available for you to use, along with a question-answering prompt for hybrid retrieval, graphrag_qa_prompt.

This exercise is part of the course

Graph RAG with LangChain and Neo4j

Exercise instructions

Pass the "question" key to the vector retriever (line_retriever) to get relevant results using vector search.
Extract the query from the graph object to execute the Cypher statement generated by the text_to_cypher_chain.
Execute graphrag_qa_chain on the input provided.

Hands-on interactive exercise

Have a go at this exercise by completing this sample code.

graphrag_qa_chain = RunnablePassthrough.assign(
    # Pass the "question" key to the retriever
    vectors = RunnableLambda(lambda x: line_retriever.invoke(____)),
    # Execute the generated Cypher statement
    records = text_to_cypher_chain | graph.____
) | graphrag_qa_prompt | llm | StrOutputParser()

# Execute the hybrid chain
output = graphrag_qa_chain.____({"question": "Does Sampson bite his thumb at Gregory?"})
print(output)

Edit and Run Code

This exercise is part of the course

Graph RAG with LangChain and Neo4j

AdvancedSkill Level

4.9+

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Learn how Graph RAG can improve the accuracy and reliability of RAG applications! Store information as nodes and edges in a Neo4j database, and give your LLM the ability to query it so it can retrieve entity and relational information to provide informed answers.

Exercise 1: Graphs and RAG Exercise 2: Creating nodes Exercise 3: Creating relationships Exercise 4: Saving graph documents Exercise 5: Querying a knowledge graph Exercise 6: Writing Cypher statements Exercise 7: Running Cypher statements Exercise 8: The MERGE clause Exercise 9: Text-to-Cypher Graph RAG with Neo4j Exercise 10: Building a text-to-Cypher chain Exercise 11: Text-to-Cypher retrieval chain

Text-to-Cypher applications work well in many circumstances, but we can do better than that! Discover how to construct graph databases using different graph models including lexical and domain graphs. Create Neo4j vector indexes so that you can have the best of both worlds and run graph and vector retrieval simultaneously!

Exercise 1: Lexical graphs Exercise 2: Elements of a lexical graph Exercise 3: Splitting the play into Acts Exercise 4: Creating a hierarchical lexical graph Exercise 5: Combining lexical graphs with vector search Exercise 6: Creating text chunks Exercise 7: Creating a vector index Exercise 8: Domain graphs Exercise 9: Creating a structured output Exercise 10: Requesting a structured output Exercise 11: Providing few-shot examples Exercise 12: Building a hybrid retrieval chain Exercise 13: Runnable lambdas Exercise 14: Assigning additional values to an input Exercise 15: The final link in the chain

Current Exercise

Although Graph RAG applications are generally more reliable than vector RAG, they aren't totally infallible. In this chapter, you'll learn to evaluate your Graph RAG applications, spot incorrect or duplicate graph nodes, and integrate long-term memory so user preferences can be learned over time.

Exercise 1: Entity resolution Exercise 2: Using extracted entities Exercise 3: Graph-based entity resolution Exercise 4: Evaluating Graph RAG with RAGAS Exercise 5: Creating a Ragas evaluation Exercise 6: Evaluating context retrieval with Ragas Exercise 7: Memory graphs Exercise 8: Saving conversation memory in the graph Exercise 9: Extracting facts from conversation histories Exercise 10: Using extracted conversation facts Exercise 11: Congratulations!