Node.jsでベクトルインデックスとOpenAIを使って質問応答システムを構築する方法

npm install @gomomento/sdk openai

import OpenAI from 'openai';
import * as https from 'https';
import { ALL_VECTOR_METADATA, CredentialProvider, PreviewVectorIndexClient, VectorIndexConfigurations, VectorSearch, VectorUpsertItemBatch } from '@gomomento/sdk';
import { CreateEmbeddingResponse } from "openai/resources";


const openai = new OpenAI({ apiKey: process.env['OPENAI_API_KEY'] });
const mviClient = new PreviewVectorIndexClient({ credentialProvider:  CredentialProvider.fromEnvironmentVariable({ environmentVariableName: 'MOMENTO_API_KEY' }), configuration: VectorIndexConfigurations.Laptop.latest() });
const indexName = 'mvi-openai-demo'

interface WikipediaResponse {
  query: {
    pages: {
      [key: string]: {
        extract: string;
      };
    };
  };
}

function getWikipediaExtract(url: string): Promise {
  return new Promise((resolve, reject) => {
    https
      .get(url, response => {
        let data = '';

        response.on('data', chunk => {
          data += chunk;
        });

        response.on('end', () => {
          try {
            const jsonData: WikipediaResponse = JSON.parse(data);
            const pages = jsonData.query.pages;
            const extract = Object.values(pages)[0].extract;
            resolve(extract);
          } catch (error) {
            reject(error);
          }
        });
      })
      .on('error', error => {
        reject(error);
      });
  });
}

const url = "https://en.wikipedia.org/w/api.php?action=query&format=json&titles=Carrot&prop=extracts&explaintext";

const extractText = await getWikipediaExtract(url);
console.log('Total characters in carrot Wikipedia page: ' + String(extractText.length));
console.log('Sample text in carrot Wikipedia page:\n\n ' + extract_text.substring(0, 500))

Total characters in carrot Wikipedia page: 21534

The carrot (Daucus carota subsp. sativus) is a root vegetable, typically orange in color, though heirloom variants including purple, black, red, white, and yellow cultivars exist, all of which are domesticated forms of the wild carrot, Daucus carota, native to Europe and Southwestern Asia. The plant probably originated in Persia and was originally cultivated for its leaves and seeds. The most commonly eaten part of the plant is the taproot, although the stems and leaves are also eaten.

function splitTextIntoChunks(text: string, chunkSize = 600): string[] {
  const chunks = [];
  for (let i = 0; i < text.length; i += chunkSize) {
    chunks.push(text.substring(i, i + chunkSize));
  }
  return chunks;
}

const chunks = splitTextIntoChunks(extractText);

console.log('Total number of chunks created: ' + String(chunks.length));
console.log('Total characters in each chunk: ' + String(chunks[0].length));

Total number of chunks created: 36
Total characters in each chunk: 600

async function generate_embeddings(chunks: string[]) {
  return await openai.embeddings.create({input: chunks, model: 'text-embedding-ada-002'});
}

const embeddingsResponse = await generateEmbeddings(chunks);

console.log('Length of each embedding: ' + String(embeddingsResponse.data[0].embedding.length));
console.log('Sample embedding: ' + String(embeddingsResponse.data[0].embedding.slice(0, 10)));

Length of each embedding: 1536

Sample embedding: 0.008307404,-0.03437371,0.00043777542,-0.01768263,-0.010926112,-0.0056728064,-0.0025742147,-0.023453956,-0.021114917,-0.020148791

async function upsertToMomentoVectorIndex(embeddingsResponse: CreateEmbeddingResponse, chunks: string[]) {
  const embeddings = embeddingsResponse.data.map(embedding => embedding.embedding);

  // Generate IDs for each chunk
  const ids = chunks.map((_, index) => `chunk${index + 1}`);

  // Generate metadata for each chunk. This will be needed when we search.
  const metadatas = chunks.map(chunk => ({text: chunk}));

  // Create VectorIndexItem objects
  const items = ids.map((id, index) => {
    return {
      id: id,
      vector: embeddings[index],
      metadata: metadatas[index],
    };
  });

  // Upsert to Momento Vector Index
  try {
    const upsertResponse = await mviClient.upsertItemBatch(indexName, items);
    if (upsertResponse instanceof VectorUpsertItemBatch.Success) {
      console.log('\n\nUpsert successful. Items have been stored');
    } else if (upsertResponse instanceof VectorUpsertItemBatch.Error) {
      console.error('Upsert error:', upsertResponse.message);
    }
  } catch (error) {
    console.error('Unexpected error during upsert:', error);
  }
}

await upsertToMomentoVectorIndex(embeddingsResponse, chunks);

Upsert successful. Items have been stored.

async function searchQuery(queryText: string): Promise {
  const queryResponse = await openai.embeddings.create({ input: queryText, model: 'text-embedding-ada-002' });
  const queryVector = queryResponse.data[0].embedding;

  try {
    const searchResponse = await mviClient.search(indexName, queryVector, {
      topK: 2,
      metadataFields: ALL_VECTOR_METADATA
    });

    if (searchResponse instanceof VectorSearch.Success) {
      const texts: string[] = searchResponse.hits().map(hit => hit.metadata.text as string);
      return texts;
    } else if (searchResponse instanceof VectorSearch.Error) {
      console.error('Search error:', searchResponse.message());
    }
  } catch (error) {
    console.error('Unexpected error during search:', error);
  }

  return [];
}

const query = 'What is a carrot?';
const texts = await searchQuery(query);
if (texts.length > 0) {
  console.log('\n=========================================\n');
  console.log('Embedding search results:\n\n', texts.join('\n'));
  console.log('\n=========================================\n');
}

The carrot (Daucus carota subsp. sativus) is a root vegetable, typically orange in color, though heirloom variants including purple, black, red, white, and yellow cultivars exist, all of which are domesticated forms of the wild carrot, Daucus carota, native to Europe and Southwestern Asia. The plant probably originated in Persia and was originally cultivated for its leaves and seeds. The most commonly eaten part of the plant is the taproot, although the stems and leaves are also eaten. The domestic carrot has been selectively bred for its enlarged, more palatable, less woody-textured taproot.

The carrot is a biennial plant in the umbellifer family, Apiaceae. At birth, it grows a rosette of leaves while building up the enlarged taproot. Fast-growing cultivars mature within about three months (90 days) of sowing the seed, while slower-maturing cultivars need a month longer (120 days). The roots contain high quantities of alpha- and beta-carotene, lycopene, anthocyanins, lutein, and are a good source of vitamin A, vitamin K, and vitamin B6. Black carrots are one of the richest sources of anthocyanins (250-300 mg/100 g fresh root weight), and hence possesses high antioxidant ability

async function searchWithChatCompletion(texts: string[], queryText: string) {
  const text = texts.join('\n');
  const prompt: string = 'Given the following extracted parts about carrot, answer questions pertaining to' +
    " carrot only from the provided text. If you don't know the answer, just say that " +
    "you don't know. Don't try to make up an answer. Do not answer anything outside of the context given. " +
    "Your job is to only answer about carrots, and only from the text below. If you don't know the answer, just " +
    "say that you don't know. Here's the text:\n\n----------------\n\n";

  const resp = await openai.chat.completions.create({
    messages: [
      { role: 'system', content: prompt + text },
      { role: 'user', content: queryText },
    ],
    model: 'gpt-3.5-turbo',
  });

  return resp;

}

const chatCompletionResp = await searchWithChatCompletion(texts, query);

console.log('\n=========================================\n');
console.log('Chat completion search results:\n\n', chatCompletionResp.choices[0].message.content);
console.log('\n=========================================\n');

A carrot is a root vegetable that is typically orange in color, although there are also other colored variants such as purple, black, red, white, and yellow.

const query = 'how fast do fast-growing cultivators mature in carrots?';
const texts = await searchQuery(query);
  if (texts.length > 0) {
    console.log('\n=========================================\n');
    console.log('Embedding search results:\n\n', texts[0]);
    console.log('\n=========================================\n');

    const chatCompletionResp = await searchWithChatCompletion(texts, query);

    console.log('\n=========================================\n');
    console.log('Chat completion search results:\n\n', chatCompletionResp.choices[0].message.content);
    console.log('\n=========================================\n');
  }

=========================================
Embedding search results:

The carrot is a biennial plant in the umbellifer family, Apiaceae. At birth, it grows a rosette of leaves while building up the enlarged taproot. Fast-growing cultivars mature within about three months (90 days) of sowing the seed, while slower-maturing cultivars need a month longer (120 days). The roots contain high quantities of alpha- and beta-carotene, lycopene, anthocyanins, lutein, and are a good source of vitamin A, vitamin K, and vitamin B6. Black carrots are one of the richest sources of anthocyanins (250-300 mg/100 g fresh root weight), and hence possesses high antioxidant ability.

=========================================


=========================================
Chat completion search results:

Fast-growing cultivars of carrots mature within about three months (90 days) of sowing the seed.

=========================================