Quickstart Guide to RAG Application Using LangChain and LlamaIndex

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db.embedded_movies.deleteMany({ plot: { $exists: false } } )
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{ acknowledged: true, deletedCount: 80 }

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import os
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from dotenv import load_dotenv
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from langchain_community.document_loaders.mongodb import MongodbLoader
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import nest_asyncio
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nest_asyncio.apply()
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load_dotenv()
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loader = MongodbLoader(
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    connection_string=os.environ['MONGODB_URI'],
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    db_name=os.environ['MONGODB_DB'],
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    collection_name=os.environ['MONGODB_COLL'],
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    filter_criteria={},
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    field_names=["title", "plot"]
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)
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docs = loader.load()
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print(len(docs))
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docs[0]

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# MongoDB URI
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# Replace <username> and <password> with your MongoDB credentials
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MONGODB_URI='mongodb+srv://<username>:<password>@kushagracluster.abcedf.mongodb.net/'
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# Name of the MongoDB database to use
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MONGODB_DB='sample_mflix'
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# Name of the MongoDB collection to use within the specified database
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MONGODB_COLL='embedded_movies'
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# API key for OpenAI.
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OPENAI_API_KEY="<OPENAI_API_KEY>"
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# Name of the index to use for vector storage
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MONGODB_VECTOR_INDEX='vector_index'
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# Name of the collection in MongoDB where embedding data is stored
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MONGODB_VECTOR_COLL_LANGCHAIN='langchain_coll'

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from pymongo import MongoClient
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from langchain.vectorstores import MongoDBAtlasVectorSearch
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from langchain_community.embeddings import OpenAIEmbeddings
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from langchain.llms import OpenAI
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from langchain_community.chat_models import ChatOpenAI
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from langchain.prompts import ChatPromptTemplate
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from langchain.chains import LLMChain
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client = MongoClient(os.environ['MONGODB_URI'], appname="devrel.content.langchain_llamaIndex.python")
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collection = client.get_database(os.environ['MONGODB_DB']).get_collection(os.environ['MONGODB_VECTOR_COLL_LANGCHAIN'])
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vector_search = MongoDBAtlasVectorSearch.from_documents(
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  documents=docs,
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  embedding=OpenAIEmbeddings(openai_api_key=os.environ['OPENAI_API_KEY']),
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  collection=collection,
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  index_name=os.environ['MONGODB_VECTOR_INDEX'])

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{
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 "_id": {
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   "$oid": "66375d1ff77b69f7b5f0c7ec"
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 },
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 "text": "The Black Pirate Seeking revenge, an athletic young man joins the pirate band responsible for his father's death....",
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 "embedding": [
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   -0.003676240383024406,
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   -0.02721614428071944,
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   ...
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   0.02543453162153851,
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]
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],
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 "database": "sample_mflix",
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 "collection": "embedded_movies"
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}

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{
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 "fields": [
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   {
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     "numDimensions": 1536,
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     "path": "embedding",
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     "similarity": "cosine",
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     "type": "vector"
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   }
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 ]
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}

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# perform a similarity search on the ingested documents
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prompt='What is the best horror movie to watch?'
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docs_with_score = vector_search.similarity_search_with_score(query=prompt,k=1)
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llm = ChatOpenAI(openai_api_key=os.environ['OPENAI_API_KEY'])
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prompt_template = ChatPromptTemplate.from_messages([
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    ("system", "You are a movie recommendation engine which posts a concise and short summary on relevant movies."),
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    ("user", "List of movies: {input}")
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])
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# Create an LLMChain
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chain = LLMChain(
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    llm=llm,
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    prompt=prompt_template
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)
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# Prepare the input for the chat model
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input_docs = "\n".join([doc.page_content for doc, _ in docs_with_score])
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# Invoke the chain with the input documents
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response = chain.invoke({"input": input_docs})
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print(response['text'])

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import os
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from llama_index.readers.mongodb import SimpleMongoReader
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reader = SimpleMongoReader(uri=os.environ["MONGODB_URI"])
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documents = reader.load_data(
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    os.environ["MONGODB_DB"],
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    os.environ["MONGODB_COLL"], 
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    field_names=["title","plot"], # these is a list of the top-level fields in your objects that will be indexed
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    query_dict={} # this is a mongo query dict that will filter your data if you don't want to index everything
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)
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print(documents[0])

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import pymongo
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import openai
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from llama_index.core import VectorStoreIndex,StorageContext
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from llama_index.vector_stores.mongodb import MongoDBAtlasVectorSearch
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# Create a new client and connect to the server
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client = pymongo.MongoClient(os.environ["MONGODB_URI"], appname="devrel.content.langchain_llamaIndex.python")
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store = MongoDBAtlasVectorSearch(
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    client,
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    db_name=os.environ['MONGODB_DB'],
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    collection_name=os.environ['MONGODB_VECTOR_COLL_LLAMAINDEX'], # this is where your embeddings will be stored
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    index_name=os.environ['MONGODB_VECTOR_INDEX'] 
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)
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storage_context = StorageContext.from_defaults(vector_store=store)
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index = VectorStoreIndex.from_documents(
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    documents, storage_context=storage_context,
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    show_progress=True, # this will show you a progress bar as the embeddings are created
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)

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{
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 "fields": [
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   {
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     "numDimensions": 1536,
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     "path": "embedding",
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     "similarity": "cosine",
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     "type": "vector"
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   }
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 ]
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}

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prompt="What is the best horror movie to watch?"
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response = index.as_query_engine(similarity_top_k=1).query(prompt)
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print(response)