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Elasticsearch

Compatibility

Only available on Node.js.

Elasticsearch is a distributed, RESTful search engine optimized for speed and relevance on production-scale workloads. It supports also vector search using the k-nearest neighbor (kNN) algorithm and also custom models for Natural Language Processing (NLP). You can read more about the support of vector search in Elasticsearch here.

LangChain.js accepts @elastic/elasticsearch as the client for Elasticsearch vectorstore.

Setup​

npm install -S @elastic/elasticsearch

You'll also need to have an Elasticsearch instance running. You can use the official Docker image to get started, or you can use Elastic Cloud, Elastic's official cloud service.

For connecting to Elastic Cloud you can read the documentation reported here for obtaining an API key.

Example: index docs, vector search and LLM integration​

Below is an example that indexes 4 documents in Elasticsearch, runs a vector search query, and finally uses an LLM to answer a question in natural language based on the retrieved documents.

tip

See this section for general instructions on installing integration packages.

npm install @langchain/openai
import { Client, ClientOptions } from "@elastic/elasticsearch";
import { OpenAI, OpenAIEmbeddings } from "@langchain/openai";
import { VectorDBQAChain } from "langchain/chains";

import {
  ElasticClientArgs,
  ElasticVectorSearch,
} from "@langchain/community/vectorstores/elasticsearch";
import { Document } from "@langchain/core/documents";

// to run this first run Elastic's docker-container with `docker-compose up -d --build`
export async function run() {
  const config: ClientOptions = {
    node: process.env.ELASTIC_URL ?? "http://127.0.0.1:9200",
  };
  if (process.env.ELASTIC_API_KEY) {
    config.auth = {
      apiKey: process.env.ELASTIC_API_KEY,
    };
  } else if (process.env.ELASTIC_USERNAME && process.env.ELASTIC_PASSWORD) {
    config.auth = {
      username: process.env.ELASTIC_USERNAME,
      password: process.env.ELASTIC_PASSWORD,
    };
  }
  const clientArgs: ElasticClientArgs = {
    client: new Client(config),
    indexName: process.env.ELASTIC_INDEX ?? "test_vectorstore",
  };

  // Index documents

  const docs = [
    new Document({
      metadata: { foo: "bar" },
      pageContent: "Elasticsearch is a powerful vector db",
    }),
    new Document({
      metadata: { foo: "bar" },
      pageContent: "the quick brown fox jumped over the lazy dog",
    }),
    new Document({
      metadata: { baz: "qux" },
      pageContent: "lorem ipsum dolor sit amet",
    }),
    new Document({
      metadata: { baz: "qux" },
      pageContent:
        "Elasticsearch a distributed, RESTful search engine optimized for speed and relevance on production-scale workloads.",
    }),
  ];

  const embeddings = new OpenAIEmbeddings();

  // await ElasticVectorSearch.fromDocuments(docs, embeddings, clientArgs);
  const vectorStore = new ElasticVectorSearch(embeddings, clientArgs);

  // Also supports an additional {ids: []} parameter for upsertion
  const ids = await vectorStore.addDocuments(docs);

  /* Search the vector DB independently with meta filters */
  const results = await vectorStore.similaritySearch("fox jump", 1);
  console.log(JSON.stringify(results, null, 2));
  /* [
        {
          "pageContent": "the quick brown fox jumped over the lazy dog",
          "metadata": {
            "foo": "bar"
          }
        }
    ]
  */

  /* Use as part of a chain (currently no metadata filters) for LLM query */
  const model = new OpenAI();
  const chain = VectorDBQAChain.fromLLM(model, vectorStore, {
    k: 1,
    returnSourceDocuments: true,
  });
  const response = await chain.invoke({ query: "What is Elasticsearch?" });

  console.log(JSON.stringify(response, null, 2));
  /*
    {
      "text": " Elasticsearch is a distributed, RESTful search engine optimized for speed and relevance on production-scale workloads.",
      "sourceDocuments": [
        {
          "pageContent": "Elasticsearch a distributed, RESTful search engine optimized for speed and relevance on production-scale workloads.",
          "metadata": {
            "baz": "qux"
          }
        }
      ]
    }
    */

  await vectorStore.delete({ ids });

  const response2 = await chain.invoke({ query: "What is Elasticsearch?" });

  console.log(JSON.stringify(response2, null, 2));

  /*
    []
  */
}

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