Skip to main content

向量存储

info

请前往Integrations查看与第三方向量存储的内置集成的文档。

存储和搜索非结构化数据的最常见方法之一是将其嵌入并存储生成的嵌入向量，然后在查询时嵌入非结构化查询并检索与嵌入查询“最相似”的嵌入向量。向量存储负责存储嵌入数据并为您执行向量搜索。

向量存储图示

入门​

本教程展示了与VectorStores相关的基本功能。与向量存储一起工作的关键部分是创建要放入其中的向量，通常是通过嵌入来创建的。因此，建议您在深入学习之前先熟悉text embedding model接口。

有许多出色的向量存储选项，以下是一些免费、开源且完全在本地机器上运行的选项。请查看所有集成以获取许多出色的托管服务。

本教程使用`chroma`向量数据库，它作为库在您的本地机器上运行。
pip install chromadb

我们想要使用OpenAIEmbeddings，所以我们需要获取OpenAI API密钥。

import os  
import getpass  

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

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

# 加载文档，将其分成块，嵌入每个块并将其加载到向量存储中。  
raw_documents = TextLoader('../../../state_of_the_union.txt').load()  
text_splitter = CharacterTextSplitter(chunk_size=1000, chunk_overlap=0)  
documents = text_splitter.split_documents(raw_documents)  
db = Chroma.from_documents(documents, OpenAIEmbeddings())

相似性搜索​

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

通过向量进行相似性搜索​

还可以使用similarity_search_by_vector进行与给定嵌入向量相似的文档搜索，该函数接受一个嵌入向量作为参数，而不是一个字符串。

embedding_vector = OpenAIEmbeddings().embed_query(query)
docs = db.similarity_search_by_vector(embedding_vector)
print(docs[0].page_content)

查询相同，结果也相同。

 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.

异步操作​

向量存储通常作为一个独立的服务运行，需要进行一些IO操作，因此可能会以异步方式调用。这样可以提高性能，因为不需要等待外部服务的响应。如果您使用异步框架（如FastAPI），这也可能很重要。

Langchain支持向量存储的异步操作。所有方法都可以使用它们的异步对应方法进行调用，前缀为a，表示async。

Qdrant是一个支持所有异步操作的向量存储，因此在本教程中将使用它。

pip install qdrant-client
from langchain.vectorstores import Qdrant

异步创建向量存储​

db = await Qdrant.afrom_documents(documents, embeddings, "http://localhost:6333")

相似性搜索​

query = "总统对Ketanji Brown Jackson说了什么"
docs = await db.asimilarity_search(query)
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.

通过向量进行相似性搜索​

embedding_vector = embeddings.embed_query(query)
docs = await db.asimilarity_search_by_vector(embedding_vector)

最大边际相关性搜索（MMR）​

最大边际相关性搜索优化了与查询的相似性和所选文档之间的多样性。它也支持异步API。

query = "What did the president say about Ketanji Brown Jackson"
found_docs = await qdrant.amax_marginal_relevance_search(query, k=2, fetch_k=10)
for i, doc in enumerate(found_docs):
    print(f"{i + 1}.", doc.page_content, "\n")
1. 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.

2. We can’t change how divided we’ve been. But we can change how we move forward—on COVID-19 and other issues we must face together.

I recently visited the New York City Police Department days after the funerals of Officer Wilbert Mora and his partner, Officer Jason Rivera.

They were responding to a 9-1-1 call when a man shot and killed them with a stolen gun.

Officer Mora was 27 years old.

Officer Rivera was 22.

Both Dominican Americans who’d grown up on the same streets they later chose to patrol as police officers.

I spoke with their families and told them that we are forever in debt for their sacrifice, and we will carry on their mission to restore the trust and safety every community deserves.

I’ve worked on these issues a long time.

I know what works: Investing in crime preventionand community police officers who’ll walk the beat, who’ll know the neighborhood, and who can restore trust and safety.