Cohere Rerank

重新排序文档可以极大地改善任何 RAG 应用程序和文档检索系统。

从高级角度来看，重新排序 API 是一个语言模型，它分析文档并根据其与给定查询的相关性重新排序它们。

Cohere 提供了一个用于重新排序文档的 API。在本例中，我们将向您展示如何使用它。

设置

提示

请参阅此部分，了解有关安装集成包的一般说明。

npm

npm install @langchain/cohere @langchain/core

Yarn

yarn add @langchain/cohere @langchain/core

pnpm

pnpm add @langchain/cohere @langchain/core

import { CohereRerank } from "@langchain/cohere";
import { Document } from "@langchain/core/documents";

const query = "What is the capital of the United States?";
const docs = [
  new Document({
    pageContent:
      "Carson City is the capital city of the American state of Nevada. At the 2010 United States Census, Carson City had a population of 55,274.",
  }),
  new Document({
    pageContent:
      "The Commonwealth of the Northern Mariana Islands is a group of islands in the Pacific Ocean that are a political division controlled by the United States. Its capital is Saipan.",
  }),
  new Document({
    pageContent:
      "Charlotte Amalie is the capital and largest city of the United States Virgin Islands. It has about 20,000 people. The city is on the island of Saint Thomas.",
  }),
  new Document({
    pageContent:
      "Washington, D.C. (also known as simply Washington or D.C., and officially as the District of Columbia) is the capital of the United States. It is a federal district. The President of the USA and many major national government offices are in the territory. This makes it the political center of the United States of America.",
  }),
  new Document({
    pageContent:
      "Capital punishment (the death penalty) has existed in the United States since before the United States was a country. As of 2017, capital punishment is legal in 30 of the 50 states. The federal government (including the United States military) also uses capital punishment.",
  }),
];

const cohereRerank = new CohereRerank({
  apiKey: process.env.COHERE_API_KEY, // Default
  model: "rerank-english-v2.0",
});

const rerankedDocuments = await cohereRerank.rerank(docs, query, {
  topN: 5,
});

console.log(rerankedDocuments);
/**
[
  { index: 3, relevanceScore: 0.9871293 },
  { index: 1, relevanceScore: 0.29961726 },
  { index: 4, relevanceScore: 0.27542195 },
  { index: 0, relevanceScore: 0.08977329 },
  { index: 2, relevanceScore: 0.041462272 }
]
 */

API 参考

• CohereRerank 来自 @langchain/cohere
• 文档 来自 @langchain/core/documents

在这里，我们可以看到 .rerank() 方法只返回文档的索引（与输入文档的索引匹配）及其相关性分数。

如果我们希望从方法本身返回文档，我们可以使用 .compressDocuments() 方法。

import { CohereRerank } from "@langchain/cohere";
import { Document } from "@langchain/core/documents";

const query = "What is the capital of the United States?";
const docs = [
  new Document({
    pageContent:
      "Carson City is the capital city of the American state of Nevada. At the 2010 United States Census, Carson City had a population of 55,274.",
  }),
  new Document({
    pageContent:
      "The Commonwealth of the Northern Mariana Islands is a group of islands in the Pacific Ocean that are a political division controlled by the United States. Its capital is Saipan.",
  }),
  new Document({
    pageContent:
      "Charlotte Amalie is the capital and largest city of the United States Virgin Islands. It has about 20,000 people. The city is on the island of Saint Thomas.",
  }),
  new Document({
    pageContent:
      "Washington, D.C. (also known as simply Washington or D.C., and officially as the District of Columbia) is the capital of the United States. It is a federal district. The President of the USA and many major national government offices are in the territory. This makes it the political center of the United States of America.",
  }),
  new Document({
    pageContent:
      "Capital punishment (the death penalty) has existed in the United States since before the United States was a country. As of 2017, capital punishment is legal in 30 of the 50 states. The federal government (including the United States military) also uses capital punishment.",
  }),
];

const cohereRerank = new CohereRerank({
  apiKey: process.env.COHERE_API_KEY, // Default
  topN: 3, // Default
  model: "rerank-english-v2.0",
});

const rerankedDocuments = await cohereRerank.compressDocuments(docs, query);

console.log(rerankedDocuments);
/**
[
  Document {
    pageContent: 'Washington, D.C. (also known as simply Washington or D.C., and officially as the District of Columbia) is the capital of the United States. It is a federal district. The President of the USA and many major national government offices are in the territory. This makes it the political center of the United States of America.',
    metadata: { relevanceScore: 0.9871293 }
  },
  Document {
    pageContent: 'The Commonwealth of the Northern Mariana Islands is a group of islands in the Pacific Ocean that are a political division controlled by the United States. Its capital is Saipan.',
    metadata: { relevanceScore: 0.29961726 }
  },
  Document {
    pageContent: 'Capital punishment (the death penalty) has existed in the United States since before the United States was a country. As of 2017, capital punishment is legal in 30 of the 50 states. The federal government (including the United States military) also uses capital punishment.',
    metadata: { relevanceScore: 0.27542195 }
  }
]
 */

API 参考

• CohereRerank 来自 @langchain/cohere
• 文档 来自 @langchain/core/documents

从结果中，我们可以看到它返回了前 3 个文档，并为每个文档分配了一个 relevanceScore。

正如预期的那样，具有最高 relevanceScore 的文档是引用华盛顿特区的文档，分数为 98.7%！