langchain/docs/modules/indexes/vectorstores/examples/pgvector.ipynb

PGVector

PGVector is an open-source vector similarity search for Postgres

It supports:

• exact and approximate nearest neighbor search
• L2 distance, inner product, and cosine distance

This notebook shows how to use the Postgres vector database (PGVector).

See the installation instruction.

In [ ]:

!pip install pgvector

We want to use OpenAIEmbeddings so we have to get the OpenAI API Key.

In [ ]:

import os
import getpass

os.environ['OPENAI_API_KEY'] = getpass.getpass('OpenAI API Key:')

In [1]:

## Loading Environment Variables
from typing import List, Tuple
from dotenv import load_dotenv
load_dotenv()

Out [1]:

False

In [4]:

from langchain.embeddings.openai import OpenAIEmbeddings
from langchain.text_splitter import CharacterTextSplitter
from langchain.vectorstores.pgvector import PGVector
from langchain.document_loaders import TextLoader
from langchain.docstore.document import Document

In [3]:

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()

In [5]:

## PGVector needs the connection string to the database.
## We will load it from the environment variables.
import os
CONNECTION_STRING = PGVector.connection_string_from_db_params(
    driver=os.environ.get("PGVECTOR_DRIVER", "psycopg2"),
    host=os.environ.get("PGVECTOR_HOST", "localhost"),
    port=int(os.environ.get("PGVECTOR_PORT", "5432")),
    database=os.environ.get("PGVECTOR_DATABASE", "postgres"),
    user=os.environ.get("PGVECTOR_USER", "postgres"),
    password=os.environ.get("PGVECTOR_PASSWORD", "postgres"),
)


## Example
# postgresql+psycopg2://username:password@localhost:5432/database_name

Similarity search with score

Similarity Search with Euclidean Distance (Default)

In [6]:

# The PGVector Module will try to create a table with the name of the collection. So, make sure that the collection name is unique and the user has the 
# permission to create a table.

db = PGVector.from_documents(
    embedding=embeddings,
    documents=docs,
    collection_name="state_of_the_union",
    connection_string=CONNECTION_STRING,
)

query = "What did the president say about Ketanji Brown Jackson"
docs_with_score: List[Tuple[Document, float]] = db.similarity_search_with_score(query)

In [7]:

for doc, score in docs_with_score:
    print("-" * 80)
    print("Score: ", score)
    print(doc.page_content)
    print("-" * 80)

--------------------------------------------------------------------------------
Score:  0.6076628081132506
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.
--------------------------------------------------------------------------------
--------------------------------------------------------------------------------
Score:  0.6076628081132506
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.
--------------------------------------------------------------------------------
--------------------------------------------------------------------------------
Score:  0.6076804780049968
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.
--------------------------------------------------------------------------------
--------------------------------------------------------------------------------
Score:  0.6076804780049968
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.
--------------------------------------------------------------------------------

Working with vectorstore in PG

Uploading a vectorstore in PG

In [ ]:

db = PGVector.from_documents(
    documents=data,
    embedding=embeddings,
    collection_name=collection_name,
    connection_string=connection_string,
    distance_strategy=DistanceStrategy.COSINE,
    openai_api_key=api_key,
    pre_delete_collection=False 
)

Retrieving a vectorstore in PG

In [ ]:

store = PGVector(
    connection_string=connection_string, 
    embedding_function=embedding, 
    collection_name=collection_name,
    distance_strategy=DistanceStrategy.COSINE
)

retriever = store.as_retriever()