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# Chroma

This notebook shows how to use functionality related to the Chroma vector database.

    from langchain.embeddings.openai import OpenAIEmbeddings
    from langchain.text_splitter import CharacterTextSplitter
    from langchain.vectorstores import Chroma
    from langchain.document_loaders import TextLoader

    from langchain.document_loaders import TextLoader
    loader = TextLoader('../../../state_of_the_union.txt')
    documents = loader.load()
    text_splitter = CharacterTextSplitter(chunk_size=1000, chunk_overlap=0)
    docs = text_splitter.split_documents(documents)

    embeddings = OpenAIEmbeddings()

    db = Chroma.from_documents(docs, embeddings)

    query = "What did the president say about Ketanji Brown Jackson"
    docs = db.similarity_search(query)

    Using embedded DuckDB without persistence: data will be transient

    print(docs[0].page_content)

    Tonight. I call on the Senate to: Pass the Freedom to Vote Act. Pass the John Lewis Voting Rights Act. And while you’re at it, pass the Disclose Act so Americans can know who is funding our elections.

    Tonight, I’d like to honor someone who has dedicated his life to serve this country: Justice Stephen Breyer—an Army veteran, Constitutional scholar, and retiring Justice of the United States Supreme Court. Justice Breyer, thank you for your service.

    One of the most serious constitutional responsibilities a President has is nominating someone to serve on the United States Supreme Court.

    And I did that 4 days ago, when I nominated Circuit Court of Appeals Judge Ketanji Brown Jackson. One of our nation’s top legal minds, who will continue Justice Breyer’s legacy of excellence.

## Similarity search with score

    docs = db.similarity_search_with_score(query)

    docs[0]

    (Document(page_content='In state after state, new laws have been passed, not only to suppress the vote, but to subvert entire elections. \n\nWe cannot let this happen. \n\nTonight. I call on the Senate to: Pass the Freedom to Vote Act. Pass the John Lewis Voting Rights Act. And while you’re at it, pass the Disclose Act so Americans can know who is funding our elections. \n\nTonight, I’d like to honor someone who has dedicated his life to serve this country: Justice Stephen Breyer—an Army veteran, Constitutional scholar, and retiring Justice of the United States Supreme Court. Justice Breyer, thank you for your service. \n\nOne of the most serious constitutional responsibilities a President has is nominating someone to serve on the United States Supreme Court. \n\nAnd I did that 4 days ago, when I nominated Circuit Court of Appeals Judge Ketanji Brown Jackson. One of our nation’s top legal minds, who will continue Justice Breyer’s legacy of excellence.', lookup_str='', metadata={'source': '../../state_of_the_union.txt'}, lookup_index=0),
     0.3913410007953644)

## Persistance

The below steps cover how to persist a ChromaDB instance

### Initialize PeristedChromaDB

Create embeddings for each chunk and insert into the Chroma vector database. The persist_directory argument tells ChromaDB where to store the database when it’s persisted.

    # Embed and store the texts
    # Supplying a persist_directory will store the embeddings on disk
    persist_directory = 'db'

    embedding = OpenAIEmbeddings()
    vectordb = Chroma.from_documents(documents=docs, embedding=embedding, persist_directory=persist_directory)

    Running Chroma using direct local API.
    No existing DB found in db, skipping load
    No existing DB found in db, skipping load

### Persist the Database

We should call persist() to ensure the embeddings are written to disk.

    vectordb.persist()
    vectordb = None

    Persisting DB to disk, putting it in the save folder db
    PersistentDuckDB del, about to run persist
    Persisting DB to disk, putting it in the save folder db

### Load the Database from disk, and create the chain

Be sure to pass the same persist_directory and embedding_function as you did when you instantiated the database. Initialize the chain we will use for question answering.

    # Now we can load the persisted database from disk, and use it as normal.
    vectordb = Chroma(persist_directory=persist_directory, embedding_function=embedding)

    Running Chroma using direct local API.
    loaded in 4 embeddings
    loaded in 1 collections

## Retriever options

This section goes over different options for how to use Chroma as a retriever.

### MMR

In addition to using similarity search in the retriever object, you can also use `mmr`.

    retriever = db.as_retriever(search_type="mmr")

    retriever.get_relevant_documents(query)[0]

    Document(page_content='Tonight. I call on the Senate to: Pass the Freedom to Vote Act. Pass the John Lewis Voting Rights Act. And while you’re at it, pass the Disclose Act so Americans can know who is funding our elections. \n\nTonight, I’d like to honor someone who has dedicated his life to serve this country: Justice Stephen Breyer—an Army veteran, Constitutional scholar, and retiring Justice of the United States Supreme Court. Justice Breyer, thank you for your service. \n\nOne of the most serious constitutional responsibilities a President has is nominating someone to serve on the United States Supreme Court. \n\nAnd I did that 4 days ago, when I nominated Circuit Court of Appeals Judge Ketanji Brown Jackson. One of our nation’s top legal minds, who will continue Justice Breyer’s legacy of excellence.', metadata={'source': '../../../state_of_the_union.txt'})