langchain-weaviate 包在 LangChain 中开始使用 Weaviate 向量存储。
Weaviate 是一个开源向量数据库。它允许您存储来自您喜欢的 ML 模型的数据对象和向量嵌入，并无缝扩展到数十亿个数据对象。要使用此集成，您需要拥有一个正在运行的 Weaviate 数据库实例。
最低版本要求
此模块需要 Weaviate1.23.7 或更高版本。但是，我们建议您使用最新版本的 Weaviate。
连接到 Weaviate
在本笔记本中，我们假设您有一个本地运行的 Weaviate 实例，地址为http://localhost:8080，并且端口 50051 已打开以用于 gRPC 流量。我们将通过以下方式连接 Weaviate：
weaviate_client = weaviate.connect_to_local()
其他部署选项
Weaviate 可以 以多种方式部署，例如使用 Weaviate Cloud Services (WCS)、Docker 或 Kubernetes。 如果您的 Weaviate 实例是通过其他方式部署的，请在此处 阅读更多 关于连接 Weaviate 的不同方法。您可以使用不同的 辅助函数 或 创建自定义实例。注意，您需要v4客户端 API，它将创建一个weaviate.WeaviateClient对象。
身份验证
某些 Weaviate 实例（例如在 WCS 上运行的实例）启用了身份验证，例如 API 密钥和/或用户名 + 密码身份验证。 请阅读 客户端身份验证指南 以获取更多信息，以及 深入的身份验证配置页面。连接到现有集合（重用索引）
如果您已经在本地 Weaviate 实例中创建了集合，可以直接连接它：from langchain_weaviate import WeaviateVectorStore
store = WeaviateVectorStore(
client=weaviate_client,
index_name="Test",
text_key="text",
)
安装
# 安装包
# pip install -Uqq langchain-weaviate
# pip install openai tiktoken langchain
环境设置
本笔记本通过OpenAIEmbeddings 使用 OpenAI API。我们建议获取 OpenAI API 密钥并将其导出为名为 OPENAI_API_KEY 的环境变量。
完成后，您的 OpenAI API 密钥将自动读取。如果您是环境变量新手，请在 Python os.environ 文档 或 本指南 中了解更多。
用法
按相似度查找对象
以下是如何根据查询的相似度查找对象的示例，从数据导入到查询 Weaviate 实例。步骤 1：数据导入
首先，我们将通过加载和分块长文本文件的内容来创建要添加到Weaviate 的数据。
from langchain_community.document_loaders import TextLoader
from langchain_openai import OpenAIEmbeddings
from langchain_text_splitters import CharacterTextSplitter
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()
/workspaces/langchain-weaviate/.venv/lib/python3.12/site-packages/langchain_core/_api/deprecation.py:117: LangChainDeprecationWarning: The class `langchain_community.embeddings.openai.OpenAIEmbeddings` was deprecated in langchain-community 0.1.0 and will be removed in 0.2.0. An updated version of the class exists in the langchain-openai package and should be used instead. To use it run `pip install -U langchain-openai` and import as `from langchain_openai import OpenAIEmbeddings`.
warn_deprecated(
weaviate_client 对象。例如，我们可以如下所示导入文档：
import weaviate
from langchain_weaviate.vectorstores import WeaviateVectorStore
weaviate_client = weaviate.connect_to_local()
db = WeaviateVectorStore.from_documents(docs, embeddings, client=weaviate_client)
/workspaces/langchain-weaviate/.venv/lib/python3.12/site-packages/pydantic/main.py:1024: PydanticDeprecatedSince20: The `dict` method is deprecated; use `model_dump` instead. Deprecated in Pydantic V2.0 to be removed in V3.0. See Pydantic V2 Migration Guide at https://errors.pydantic.dev/2.6/migration/
warnings.warn('The `dict` method is deprecated; use `model_dump` instead.', category=PydanticDeprecatedSince20)
步骤 2：执行搜索
我们现在可以执行相似度搜索。这将返回与查询文本最相似的文档，基于存储在 Weaviate 中的嵌入和从查询文本生成的等效嵌入。query = "What did the president say about Ketanji Brown Jackson"
docs = db.similarity_search(query)
# Print the first 100 characters of each result
for i, doc in enumerate(docs):
print(f"\nDocument {i + 1}:")
print(doc.page_content[:100] + "...")
Document 1:
Tonight. I call on the Senate to: Pass the Freedom to Vote Act. Pass the John Lewis Voting Rights Ac...
Document 2:
And so many families are living paycheck to paycheck, struggling to keep up with the rising cost of ...
Document 3:
Vice President Harris and I ran for office with a new economic vision for America.
Invest in Ameri...
Document 4:
A former top litigator in private practice. A former federal public defender. And from a family of p...
from weaviate.classes.query import Filter
for filter_str in ["blah.txt", "state_of_the_union.txt"]:
search_filter = Filter.by_property("source").equal(filter_str)
filtered_search_results = db.similarity_search(query, filters=search_filter)
print(len(filtered_search_results))
if filter_str == "state_of_the_union.txt":
assert len(filtered_search_results) > 0 # 应该至少有一个结果
else:
assert len(filtered_search_results) == 0 # 应该没有结果
0
4
k，这是要返回的结果数量的上限。
search_filter = Filter.by_property("source").equal("state_of_the_union.txt")
filtered_search_results = db.similarity_search(query, filters=search_filter, k=3)
assert len(filtered_search_results) <= 3
量化结果相似度
您可以选择检索相关性“分数”。这是一个相对分数，表示特定搜索结果在搜索结果池中的好坏程度。 请注意，这是相对分数，意味着不应将其用于确定相关性的阈值。但是，它可以用于在整个搜索结果集中比较不同搜索结果的相关性。docs = db.similarity_search_with_score("country", k=5)
for doc in docs:
print(f"{doc[1]:.3f}", ":", doc[0].page_content[:100] + "...")
0.935 : For that purpose we’ve mobilized American ground forces, air squadrons, and ship deployments to prot...
0.500 : And built the strongest, freest, and most prosperous nation the world has ever known.
Now is the h...
0.462 : If you travel 20 miles east of Columbus, Ohio, you’ll find 1,000 empty acres of land.
It won’t loo...
0.450 : And my report is this: the State of the Union is strong—because you, the American people, are strong...
0.442 : Tonight. I call on the Senate to: Pass the Freedom to Vote Act. Pass the John Lewis Voting Rights Ac...
搜索机制
similarity_search 使用 Weaviate 的 混合搜索。
混合搜索结合向量和关键词搜索，其中 alpha 是向量搜索的权重。similarity_search 函数允许您作为 kwargs 传递额外参数。有关可用参数，请参阅此 参考文档。
您可以通过添加 alpha=0 执行纯关键词搜索，如下所示：
docs = db.similarity_search(query, alpha=0)
docs[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'})
持久性
通过langchain-weaviate 添加的任何数据将根据其配置在 Weaviate 中持久化。
例如，WCS 实例配置为无限期持久化数据，Docker 实例可以设置为在卷中持久化数据。阅读更多关于 Weaviate 的持久性 的信息。
多租户
多租户 允许您在单个 Weaviate 实例中拥有大量隔离的数据集合，具有相同的集合配置。这对于多用户环境非常有用，例如构建 SaaS 应用程序，其中每个最终用户都将拥有自己隔离的数据集合。 要使用多租户，向量存储需要知道tenant 参数。
添加任何数据时，提供 tenant 参数，如下所示。
db_with_mt = WeaviateVectorStore.from_documents(
docs, embeddings, client=weaviate_client, tenant="Foo"
)
2024-Mar-26 03:40 PM - langchain_weaviate.vectorstores - INFO - Tenant Foo does not exist in index LangChain_30b9273d43b3492db4fb2aba2e0d6871. Creating tenant.
tenant 参数。
db_with_mt.similarity_search(query, tenant="Foo")
[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'}),
Document(page_content='And so many families are living paycheck to paycheck, struggling to keep up with the rising cost of food, gas, housing, and so much more. \n\nI understand. \n\nI remember when my Dad had to leave our home in Scranton, Pennsylvania to find work. I grew up in a family where if the price of food went up, you felt it. \n\nThat’s why one of the first things I did as President was fight to pass the American Rescue Plan. \n\nBecause people were hurting. We needed to act, and we did. \n\nFew pieces of legislation have done more in a critical moment in our history to lift us out of crisis. \n\nIt fueled our efforts to vaccinate the nation and combat COVID-19. It delivered immediate economic relief for tens of millions of Americans. \n\nHelped put food on their table, keep a roof over their heads, and cut the cost of health insurance. \n\nAnd as my Dad used to say, it gave people a little breathing room.', metadata={'source': 'state_of_the_union.txt'}),
Document(page_content='He and his Dad both have Type 1 diabetes, which means they need insulin every day. Insulin costs about $10 a vial to make. \n\nBut drug companies charge families like Joshua and his Dad up to 30 times more. I spoke with Joshua’s mom. \n\nImagine what it’s like to look at your child who needs insulin and have no idea how you’re going to pay for it. \n\nWhat it does to your dignity, your ability to look your child in the eye, to be the parent you expect to be. \n\nJoshua is here with us tonight. Yesterday was his birthday. Happy birthday, buddy. \n\nFor Joshua, and for the 200,000 other young people with Type 1 diabetes, let’s cap the cost of insulin at $35 a month so everyone can afford it. \n\nDrug companies will still do very well. And while we’re at it let Medicare negotiate lower prices for prescription drugs, like the VA already does.', metadata={'source': 'state_of_the_union.txt'}),
Document(page_content='Putin’s latest attack on Ukraine was premeditated and unprovoked. \n\nHe rejected repeated efforts at diplomacy. \n\nHe thought the West and NATO wouldn’t respond. And he thought he could divide us at home. Putin was wrong. We were ready. Here is what we did. \n\nWe prepared extensively and carefully. \n\nWe spent months building a coalition of other freedom-loving nations from Europe and the Americas to Asia and Africa to confront Putin. \n\nI spent countless hours unifying our European allies. We shared with the world in advance what we knew Putin was planning and precisely how he would try to falsely justify his aggression. \n\nWe countered Russia’s lies with truth. \n\nAnd now that he has acted the free world is holding him accountable. \n\nAlong with twenty-seven members of the European Union including France, Germany, Italy, as well as countries like the United Kingdom, Canada, Japan, Korea, Australia, New Zealand, and many others, even Switzerland.', metadata={'source': 'state_of_the_union.txt'})]
检索器选项
Weaviate 也可用作检索器最大边际相关性搜索 (MMR)
除了在使用检索器对象中使用相似度搜索外，您还可以使用mmr。
retriever = db.as_retriever(search_type="mmr")
retriever.invoke(query)[0]
/workspaces/langchain-weaviate/.venv/lib/python3.12/site-packages/pydantic/main.py:1024: PydanticDeprecatedSince20: The `dict` method is deprecated; use `model_dump` instead. Deprecated in Pydantic V2.0 to be removed in V3.0. See Pydantic V2 Migration Guide at https://errors.pydantic.dev/2.6/migration/
warnings.warn('The `dict` method is deprecated; use `model_dump` instead.', category=PydanticDeprecatedSince20)
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'})
与 LangChain 配合使用
大型语言模型 (LLM) 的一个已知限制是其训练数据可能过时，或不包含您所需的特定领域知识。 查看下面的示例：from langchain_openai import ChatOpenAI
llm = ChatOpenAI(model="gpt-3.5-turbo", temperature=0)
llm.predict("What did the president say about Justice Breyer")
/workspaces/langchain-weaviate/.venv/lib/python3.12/site-packages/langchain_core/_api/deprecation.py:117: LangChainDeprecationWarning: The class `langchain_community.chat_models.openai.ChatOpenAI` was deprecated in langchain-community 0.0.10 and will be removed in 0.2.0. An updated version of the class exists in the langchain-openai package and should be used instead. To use it run `pip install -U langchain-openai` and import as `from langchain_openai import ChatOpenAI`.
warn_deprecated(
/workspaces/langchain-weaviate/.venv/lib/python3.12/site-packages/langchain_core/_api/deprecation.py:117: LangChainDeprecationWarning: The function `predict` was deprecated in LangChain 0.1.7 and will be removed in 0.2.0. Use invoke instead.
warn_deprecated(
/workspaces/langchain-weaviate/.venv/lib/python3.12/site-packages/pydantic/main.py:1024: PydanticDeprecatedSince20: The `dict` method is deprecated; use `model_dump` instead. Deprecated in Pydantic V2.0 to be removed in V3.0. See Pydantic V2 Migration Guide at https://errors.pydantic.dev/2.6/migration/
warnings.warn('The `dict` method is deprecated; use `model_dump` instead.', category=PydanticDeprecatedSince20)
"I'm sorry, I cannot provide real-time information as my responses are generated based on a mixture of licensed data, data created by human trainers, and publicly available data. The last update was in October 2021."
- 问答
- 检索增强生成 (RAG)
带来源的问答
LangChain 中的问答可以通过使用向量存储来增强。让我们看看如何实现这一点。 本节使用RetrievalQAWithSourcesChain，它执行从索引中查找文档的操作。
首先，我们将再次对文本进行分块并将它们导入到 Weaviate 向量存储中。
from langchain_classic.chains import RetrievalQAWithSourcesChain
from langchain_openai import OpenAI
with open("state_of_the_union.txt") as f:
state_of_the_union = f.read()
text_splitter = CharacterTextSplitter(chunk_size=1000, chunk_overlap=0)
texts = text_splitter.split_text(state_of_the_union)
docsearch = WeaviateVectorStore.from_texts(
texts,
embeddings,
client=weaviate_client,
metadatas=[{"source": f"{i}-pl"} for i in range(len(texts))],
)
chain = RetrievalQAWithSourcesChain.from_chain_type(
OpenAI(temperature=0), chain_type="stuff", retriever=docsearch.as_retriever()
)
/workspaces/langchain-weaviate/.venv/lib/python3.12/site-packages/langchain_core/_api/deprecation.py:117: LangChainDeprecationWarning: The class `langchain_community.llms.openai.OpenAI` was deprecated in langchain-community 0.0.10 and will be removed in 0.2.0. An updated version of the class exists in the langchain-openai package and should be used instead. To use it run `pip install -U langchain-openai` and import as `from langchain_openai import OpenAI`.
warn_deprecated(
chain(
{"question": "What did the president say about Justice Breyer"},
return_only_outputs=True,
)
/workspaces/langchain-weaviate/.venv/lib/python3.12/site-packages/langchain_core/_api/deprecation.py:117: LangChainDeprecationWarning: The function `__call__` was deprecated in LangChain 0.1.0 and will be removed in 0.2.0. Use invoke instead.
warn_deprecated(
/workspaces/langchain-weaviate/.venv/lib/python3.12/site-packages/pydantic/main.py:1024: PydanticDeprecatedSince20: The `dict` method is deprecated; use `model_dump` instead. Deprecated in Pydantic V2.0 to be removed in V3.0. See Pydantic V2 Migration Guide at https://errors.pydantic.dev/2.6/migration/
warnings.warn('The `dict` method is deprecated; use `model_dump` instead.', category=PydanticDeprecatedSince20)
/workspaces/langchain-weaviate/.venv/lib/python3.12/site-packages/pydantic/main.py:1024: PydanticDeprecatedSince20: The `dict` method is deprecated; use `model_dump` instead. Deprecated in Pydantic V2.0 to be removed in V3.0. See Pydantic V2 Migration Guide at https://errors.pydantic.dev/2.6/migration/
warnings.warn('The `dict` method is deprecated; use `model_dump` instead.', category=PydanticDeprecatedSince20)
{'answer': ' The president thanked Justice Stephen Breyer for his service and announced his nomination of Judge Ketanji Brown Jackson to the Supreme Court.\n',
'sources': '31-pl'}
检索增强生成
结合 LLM 和向量存储的另一个非常流行的应用是检索增强生成 (RAG)。这是一种使用检索器从向量存储中查找相关信息，然后使用 LLM 基于检索到的数据和提示提供输出的技术。 我们从类似的设置开始：with open("state_of_the_union.txt") as f:
state_of_the_union = f.read()
text_splitter = CharacterTextSplitter(chunk_size=1000, chunk_overlap=0)
texts = text_splitter.split_text(state_of_the_union)
docsearch = WeaviateVectorStore.from_texts(
texts,
embeddings,
client=weaviate_client,
metadatas=[{"source": f"{i}-pl"} for i in range(len(texts))],
)
retriever = docsearch.as_retriever()
from langchain_core.prompts import ChatPromptTemplate
template = """You are an assistant for question-answering tasks. Use the following pieces of retrieved context to answer the question. If you don't know the answer, just say that you don't know. Use three sentences maximum and keep the answer concise.
Question: {question}
Context: {context}
Answer:
"""
prompt = ChatPromptTemplate.from_template(template)
print(prompt)
input_variables=['context', 'question'] messages=[HumanMessagePromptTemplate(prompt=PromptTemplate(input_variables=['context', 'question'], template="You are an assistant for question-answering tasks. Use the following pieces of retrieved context to answer the question. If you don't know the answer, just say that you don't know. Use three sentences maximum and keep the answer concise.\nQuestion: {question}\nContext: {context}\nAnswer:\n"))]
from langchain_openai import ChatOpenAI
llm = ChatOpenAI(model="gpt-3.5-turbo", temperature=0)
from langchain_core.output_parsers import StrOutputParser
from langchain_core.runnables import RunnablePassthrough
rag_chain = (
{"context": retriever, "question": RunnablePassthrough()}
| prompt
| llm
| StrOutputParser()
)
rag_chain.invoke("What did the president say about Justice Breyer")
/workspaces/langchain-weaviate/.venv/lib/python3.12/site-packages/pydantic/main.py:1024: PydanticDeprecatedSince20: The `dict` method is deprecated; use `model_dump` instead. Deprecated in Pydantic V2.0 to be removed in V3.0. See Pydantic V2 Migration Guide at https://errors.pydantic.dev/2.6/migration/
warnings.warn('The `dict` method is deprecated; use `model_dump` instead.', category=PydanticDeprecatedSince20)
/workspaces/langchain-weaviate/.venv/lib/python3.12/site-packages/pydantic/main.py:1024: PydanticDeprecatedSince20: The `dict` method is deprecated; use `model_dump` instead. Deprecated in Pydantic V2.0 to be removed in V3.0. See Pydantic V2 Migration Guide at https://errors.pydantic.dev/2.6/migration/
warnings.warn('The `dict` method is deprecated; use `model_dump` instead.', category=PydanticDeprecatedSince20)
"The president honored Justice Stephen Breyer for his service to the country as an Army veteran, Constitutional scholar, and retiring Justice of the United States Supreme Court. The president also mentioned nominating Circuit Court of Appeals Judge Ketanji Brown Jackson to continue Justice Breyer's legacy of excellence. The president expressed gratitude towards Justice Breyer and highlighted the importance of nominating someone to serve on the United States Supreme Court."
总结与资源
Weaviate 是一个可扩展、生产就绪的向量存储。 此集成允许 Weaviate 与 LangChain 一起使用，通过强大的数据存储增强大型语言模型的功能。其可扩展性和生产就绪性使其成为 LangChain 应用程序向量存储的绝佳选择，并将减少您的生产时间。Connect these docs to Claude, VSCode, and more via MCP for real-time answers.