Azure Cosmos DB for NoSQL 支持查询具有灵活模式的项目，并原生支持 JSON。它现在提供向量索引和搜索。此功能旨在处理高维向量，从而实现任何规模的高效且准确的向量搜索。您现在可以将向量直接存储在文档中，与您的数据一起。数据库中的每个文档不仅可以包含传统的无模式数据，还可以包含作为文档其他属性的高维向量。
从 此页面 了解如何利用 Azure Cosmos DB for NoSQL 的向量搜索功能。如果您没有 Azure 帐户，您可以 创建一个免费帐户 以开始使用。
您首先需要安装 @langchain/azure-cosmosdb 包：
请参阅 此部分 以获取有关安装 LangChain 包的一般说明。 npm install @langchain/azure-cosmosdb @langchain/core
# Use connection string to authenticate
AZURE_COSMOSDB_NOSQL_CONNECTION_STRING=
# Use managed identity to authenticate
AZURE_COSMOSDB_NOSQL_ENDPOINT=
使用 Azure 托管标识
如果您使用的是 Azure 托管标识，则可以按如下方式配置凭据：
import { AzureCosmosDBNoSQLVectorStore } from "@langchain/azure-cosmosdb";
import { OpenAIEmbeddings } from "@langchain/openai";
// Create Azure Cosmos DB vector store
const store = new AzureCosmosDBNoSQLVectorStore(new OpenAIEmbeddings(), {
// Or use environment variable AZURE_COSMOSDB_NOSQL_ENDPOINT
endpoint: "https://my-cosmosdb.documents.azure.com:443/",
// Database and container must already exist
databaseName: "my-database",
containerName: "my-container",
});
当使用 Azure 托管标识和基于角色的访问控制时，必须确保已预先创建数据库和容器。RBAC 不提供创建数据库和容器的权限。您可以在 Azure Cosmos DB 文档 中获取有关权限模型的更多信息。 使用过滤器时的安全注意事项
如果未正确清理数据，使用带有用户提供的输入的过滤器可能会带来安全风险。请遵循以下建议以防止潜在的安全问题。
WHERE ${userFilter} - 会引入 SQL 注入攻击的严重风险，可能会暴露意外数据或损害系统的完整性。为了减轻这种情况，请始终使用 Azure Cosmos DB 的参数化查询机制，传入 @param 占位符，这将查询逻辑与用户提供的输入完全分开。
这是一个不安全代码的示例：
import { AzureCosmosDBNoSQLVectorStore } from "@langchain/azure-cosmosdb";
const store = new AzureCosmosDBNoSQLVectorStore(embeddings, {});
// Unsafe: user-controlled input injected into the query
const userId = req.query.userId; // e.g. "123' OR 1=1"
const unsafeQuerySpec = {
query: `SELECT * FROM c WHERE c.metadata.userId = '${userId}'`,
};
await store.delete({ filter: unsafeQuerySpec });
123 OR 1=1，那么查询将变为 SELECT * FROM c WHERE c.metadata.userId = '123' OR 1=1，这将强制条件始终为真，从而导致它绕过预期的过滤器并删除所有文档。
为了防止这种注入风险，您定义一个像 @userId 这样的占位符，Cosmos DB 将用户输入作为参数单独绑定，确保它被严格视为数据而不是可执行的查询逻辑，如下所示。
import { SqlQuerySpec } from "@azure/cosmos";
const safeQuerySpec: SqlQuerySpec = {
query: "SELECT * FROM c WHERE c.metadata.userId = @userId",
parameters: [{ name: "@userId", value: userId }],
};
await store.delete({ filter: safeQuerySpec });
123 OR 1=1，输入将被视为要匹配的文字字符串值，而不是查询结构的一部分。
请参阅有关 Azure Cosmos DB for NoSQL 中的参数化查询 的官方文档，以获取更多使用示例和最佳实践。
使用示例
下面是一个示例，它在 Azure Cosmos DB for NoSQL 中索引文件中的文档，运行向量搜索查询，最后使用链根据检索到的文档以自然语言回答问题。
import { AzureCosmosDBNoSQLVectorStore } from "@langchain/azure-cosmosdb";
import { ChatPromptTemplate } from "@langchain/core/prompts";
import { ChatOpenAI, OpenAIEmbeddings } from "@langchain/openai";
import { createStuffDocumentsChain } from "@langchain/classic/chains/combine_documents";
import { createRetrievalChain } from "@langchain/classic/chains/retrieval";
import { TextLoader } from "@langchain/classic/document_loaders/fs/text";
import { RecursiveCharacterTextSplitter } from "@langchain/textsplitters";
// Load documents from file
const loader = new TextLoader("./state_of_the_union.txt");
const rawDocuments = await loader.load();
const splitter = new RecursiveCharacterTextSplitter({
chunkSize: 1000,
chunkOverlap: 0,
});
const documents = await splitter.splitDocuments(rawDocuments);
// Create Azure Cosmos DB vector store
const store = await AzureCosmosDBNoSQLVectorStore.fromDocuments(
documents,
new OpenAIEmbeddings(),
{
databaseName: "langchain",
containerName: "documents",
}
);
// Performs a similarity search
const resultDocuments = await store.similaritySearch(
"What did the president say about Ketanji Brown Jackson?"
);
console.log("Similarity search results:");
console.log(resultDocuments[0].pageContent);
/*
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.
*/
// Use the store as part of a chain
const model = new ChatOpenAI({ model: "gpt-3.5-turbo-1106" });
const questionAnsweringPrompt = ChatPromptTemplate.fromMessages([
[
"system",
"Answer the user's questions based on the below context:\n\n{context}",
],
["human", "{input}"],
]);
const combineDocsChain = await createStuffDocumentsChain({
llm: model,
prompt: questionAnsweringPrompt,
});
const chain = await createRetrievalChain({
retriever: store.asRetriever(),
combineDocsChain,
});
const res = await chain.invoke({
input: "What is the president's top priority regarding prices?",
});
console.log("Chain response:");
console.log(res.answer);
/*
The president's top priority is getting prices under control.
*/
// Clean up
await store.delete();
