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PGVecto.rs

本笔记本展示了如何使用与Postgres向量数据库(pgvecto.rs)相关的功能。

%pip install "pgvecto_rs[sdk]" langchain-community
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from typing import List

from langchain_community.document_loaders import TextLoader
from langchain_community.embeddings.fake import FakeEmbeddings
from langchain_community.vectorstores.pgvecto_rs import PGVecto_rs
from langchain_core.documents import Document
from langchain_text_splitters import CharacterTextSplitter
loader = TextLoader("../../how_to/state_of_the_union.txt")
documents = loader.load()
text_splitter = CharacterTextSplitter(chunk_size=1000, chunk_overlap=0)
docs = text_splitter.split_documents(documents)

embeddings = FakeEmbeddings(size=3)

使用官方演示Docker镜像启动数据库。

! docker run --name pgvecto-rs-demo -e POSTGRES_PASSWORD=mysecretpassword -p 5432:5432 -d tensorchord/pgvecto-rs:latest

然后构建数据库URL。

## PGVecto.rs needs the connection string to the database.
## We will load it from the environment variables.
import os

PORT = os.getenv("DB_PORT", 5432)
HOST = os.getenv("DB_HOST", "localhost")
USER = os.getenv("DB_USER", "postgres")
PASS = os.getenv("DB_PASS", "mysecretpassword")
DB_NAME = os.getenv("DB_NAME", "postgres")

# Run tests with shell:
URL = "postgresql+psycopg://{username}:{password}@{host}:{port}/{db_name}".format(
port=PORT,
host=HOST,
username=USER,
password=PASS,
db_name=DB_NAME,
)

最后,从文档中创建VectorStore:

db1 = PGVecto_rs.from_documents(
documents=docs,
embedding=embeddings,
db_url=URL,
# The table name is f"collection_{collection_name}", so that it should be unique.
collection_name="state_of_the_union",
)

您可以稍后通过以下方式连接到表:

# Create new empty vectorstore with collection_name.
# Or connect to an existing vectorstore in database if exists.
# Arguments should be the same as when the vectorstore was created.
db1 = PGVecto_rs.from_collection_name(
embedding=embeddings,
db_url=URL,
collection_name="state_of_the_union",
)

确保用户被允许创建表。

带分数的相似性搜索

使用欧几里得距离的相似性搜索(默认)

query = "What did the president say about Ketanji Brown Jackson"
docs: List[Document] = db1.similarity_search(query, k=4)
for doc in docs:
print(doc.page_content)
print("======================")

带过滤器的相似性搜索

from pgvecto_rs.sdk.filters import meta_contains

query = "What did the president say about Ketanji Brown Jackson"
docs: List[Document] = db1.similarity_search(
query, k=4, filter=meta_contains({"source": "../../how_to/state_of_the_union.txt"})
)

for doc in docs:
print(doc.page_content)
print("======================")

或者:

query = "What did the president say about Ketanji Brown Jackson"
docs: List[Document] = db1.similarity_search(
query, k=4, filter={"source": "../../how_to/state_of_the_union.txt"}
)

for doc in docs:
print(doc.page_content)
print("======================")

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