适合新手做的网站静态培训后的收获和感想
在我之前的文章 “Elasticsearch：ES|QL 查询 TypeScript 类型（一）”，我们讲述了如何在 Nodejs 里对 ES|QL 进行查询。在今天的文章中，我们来使用一个完整的例子来进行详细描述。更多有关如何使用 Nodejs 来访问 Elasticsearch的知识，请参阅文章 “Elasticsearch：使用最新的 Nodejs client 8.x 来创建索引并搜索”。
在一下的演示中，我将使用 Elastic Stack 8.13.4 来进行展示。
安装
Elasticsearch 及 Kibana
如果你还没有安装好自己的 Elasticsearch 及 Kibana，请参考如下的链接来进行安装：
- 如何在 Linux，MacOS 及 Windows 上进行安装 Elasticsearch
- Kibana：如何在 Linux，MacOS 及 Windows上安装 Elastic 栈中的 Kibana
在安装的时候，我们选择 Elastic Stack 8.x 来进行安装。特别值得指出的是：ES|QL 只在 Elastic Stack 8.11 及以后得版本中才有。你需要下载 Elastic Stack 8.11 及以后得版本来进行安装。
在首次启动 Elasticsearch 的时候，我们可以看到如下的输出：
我们需要记下 Elasticsearch 超级用户 elastic 的密码。
我们还可以在安装 Elasticsearch 目录中找到 Elasticsearch 的访问证书：
$ pwd
/Users/liuxg/elastic/elasticsearch-8.13.4/config/certs
$ ls
http.p12 http_ca.crt transport.p12在上面，http_ca.crt 是我们需要用来访问 Elasticsearch 的证书。
Nodejs 依赖包
我们可以使用如下的命令来安装最新的 nodejs 客户端包：
yarn add @elastic/elasticsearch或者npm install @elastic/elasticsearch我们可以通过如下的命令来查看安装的版本：
$ npm -v @elastic/elasticsearch
8.19.2创建项目目录并拷贝证书
我们在电脑里创建一个目录，并拷贝相应的 Elasticsearch 访问证书到该目录下：
$ pwd
/Users/liuxg/nodejs/esql
$ cp ~/elastic/elasticsearch-8.13.4/config/certs/http_ca.crt .
$ ls http_ca.crt
http_ca.crt
我们使用如下的命令来安装：
npm install --save-dev @types/node创建一个叫做 esql.ts 的文件
touch esql.ts我们使用如下的命令来安装 ts-node：
npm install -g ts-node typescript '@types/node'在下面我们将使用如下的命令来运行代码：
ts-node esql.ts 展示
连接到 Elasticsearch
我们编辑 esql.ts 如下：
import { Client } from '@elastic/elasticsearch'
import * as fs from "fs";const client = new Client({node: 'https://localhost:9200',auth: {username: 'elastic',password: '=VnaMJck+DbYXpHR1Fch'},tls: {ca: fs.readFileSync('./http_ca.crt'),rejectUnauthorized: false}})client.info().then((response) => console.log(JSON.stringify(response))).catch((error) => console.error(JSON.stringify(error))); 在上面，我们使用超级账号 elastic 来进行连接。我们使用证书来访问自签名证书的集群。你需要根据自己的 Elasticsearch 配置修改上面的代码。更多关于如何访问 Elasticsearch 的知识，请阅读文章 “Elasticsearch：使用最新的 Nodejs client 8.x 来创建索引并搜索”。 运行上面的代码，返回：
$ ts-node esql.ts
{"name":"liuxgm.local","cluster_name":"elasticsearch","cluster_uuid":"JXoZ_Xu-QnasteO4AWnVvQ","version":{"number":"8.13.4","build_flavor":"default","build_type":"tar","build_hash":"da95df118650b55a500dcc181889ac35c6d8da7c","build_date":"2024-05-06T22:04:45.107454559Z","build_snapshot":false,"lucene_version":"9.10.0","minimum_wire_compatibility_version":"7.17.0","minimum_index_compatibility_version":"7.0.0"},"tagline":"You Know, for Search"}写入数据
esql.ts
import { Client } from '@elastic/elasticsearch'
import * as fs from "fs";const client = new Client({node: 'https://localhost:9200',auth: {username: 'elastic',password: '=VnaMJck+DbYXpHR1Fch'},tls: {ca: fs.readFileSync('./http_ca.crt'),rejectUnauthorized: false}})client.info().then((response) => console.log(JSON.stringify(response))).catch((error) => console.error(JSON.stringify(error))); async function run () {// Lets index some data into Elasticsearchawait client.indices.exists({index: "books"}).then(function (exists) {if(exists) {console.log("the index already existed")} else {console.log("the index has not been createdyet")client.helpers.bulk({datasource: [{ name: "Revelation Space", author: "Alastair Reynolds", release_date: "2000-03-15", page_count: 585 },{ name: "1984", author: "George Orwell", release_date: "1985-06-01", page_count: 328 },{ name: "Fahrenheit 451", author: "Ray Bradbury", release_date: "1953-10-15", page_count: 227 },{ name: "Brave New World", author: "Aldous Huxley", release_date: "1932-06-01", page_count: 268 },],onDocument(_doc) {return { index: { _index: "books" } }},})}})
}run().catch(console.log)在运行完上面的代码后，我们可以在 Kibana 中进行查看：
对数据进行 ES|QL 查询
const response = await client.esql.query({ query: 'FROM books' })console.log(response)完整的代码为：
esql.ts
import { Client } from '@elastic/elasticsearch'
import * as fs from "fs";const client = new Client({node: 'https://localhost:9200',auth: {username: 'elastic',password: '=VnaMJck+DbYXpHR1Fch'},tls: {ca: fs.readFileSync('./http_ca.crt'),rejectUnauthorized: false}})client.info().then((response) => console.log(JSON.stringify(response))).catch((error) => console.error(JSON.stringify(error))); async function run () {// Lets index some data into Elasticsearchawait client.indices.exists({index: "books"}).then(function (exists) {if(exists) {console.log("the index already existed")} else {console.log("the index has not been createdyet")client.helpers.bulk({datasource: [{ name: "Revelation Space", author: "Alastair Reynolds", release_date: "2000-03-15", page_count: 585 },{ name: "1984", author: "George Orwell", release_date: "1985-06-01", page_count: 328 },{ name: "Fahrenheit 451", author: "Ray Bradbury", release_date: "1953-10-15", page_count: 227 },{ name: "Brave New World", author: "Aldous Huxley", release_date: "1932-06-01", page_count: 268 },],onDocument(_doc) {return { index: { _index: "books" } }},})}})const response = await client.esql.query({ query: 'FROM books' })console.log(response)
}run().catch(console.log)上面代码的完整响应为：
$ ts-node esql.ts
the index already existed
{"name":"liuxgm.local","cluster_name":"elasticsearch","cluster_uuid":"JXoZ_Xu-QnasteO4AWnVvQ","version":{"number":"8.13.4","build_flavor":"default","build_type":"tar","build_hash":"da95df118650b55a500dcc181889ac35c6d8da7c","build_date":"2024-05-06T22:04:45.107454559Z","build_snapshot":false,"lucene_version":"9.10.0","minimum_wire_compatibility_version":"7.17.0","minimum_index_compatibility_version":"7.0.0"},"tagline":"You Know, for Search"}
{columns: [{ name: 'author', type: 'text' },{ name: 'author.keyword', type: 'keyword' },{ name: 'name', type: 'text' },{ name: 'name.keyword', type: 'keyword' },{ name: 'page_count', type: 'long' },{ name: 'release_date', type: 'date' }],values: [['Alastair Reynolds','Alastair Reynolds','Revelation Space','Revelation Space',585,'2000-03-15T00:00:00.000Z'],['George Orwell','George Orwell','1984','1984',328,'1985-06-01T00:00:00.000Z'],['Ray Bradbury','Ray Bradbury','Fahrenheit 451','Fahrenheit 451',227,'1953-10-15T00:00:00.000Z'],['Aldous Huxley','Aldous Huxley','Brave New World','Brave New World',268,'1932-06-01T00:00:00.000Z']]
}
将每行返回为值数组是一个简单的默认设置，在许多情况下很有用。不过，如果你想要一个记录数组（JavaScript 应用程序中的标准结构），则需要额外的努力来转换数据。
幸运的是，在 8.14.0 中，JavaScript 客户端将包含一个新的 ES|QL 助手来为你执行此操作：
const { records } = await client.helpers.esql({ query: 'FROM books' }).toRecords()/*
Returns:
[{ name: "Revelation Space", author: "Alastair Reynolds", release_date: "2000-03-15", page_count: 585 },{ name: "1984", author: "George Orwell", release_date: "1985-06-01", page_count: 328 },{ name: "Fahrenheit 451", author: "Ray Bradbury", release_date: "1953-10-15", page_count: 227 },{ name: "Brave New World", author: "Aldous Huxley", release_date: "1932-06-01", page_count: 268 },
]
*/截止目前为止，8.14 还没有发布。期待在正式发布后，我们再重新尝试。
更多关于 ES|QL 的查询，请详细阅读文章 “Elasticsearch：ES|QL 动手实践”。
在文章的最后，我们可以来完成另外一个查询。我们使用 Kibana 来进行查询：
POST _query?format=txt
{"query": """FROM books| WHERE release_date > "1985-06-01"| LIMIT 5"""
}
我们使用 Nodejs 来进行查询：
const query = 'FROM books | WHERE release_date > "1985-06-01" | LIMIT 5'const response1 = await client.esql.query({ query: query })console.log(response1)esql.ts
import { Client } from '@elastic/elasticsearch'
import * as fs from "fs";const client = new Client({node: 'https://localhost:9200',auth: {username: 'elastic',password: '=VnaMJck+DbYXpHR1Fch'},tls: {ca: fs.readFileSync('./http_ca.crt'),rejectUnauthorized: false}})client.info().then((response) => console.log(JSON.stringify(response))).catch((error) => console.error(JSON.stringify(error))); async function run () {// Lets index some data into Elasticsearchawait client.indices.exists({index: "books"}).then(function (exists) {if(exists) {console.log("the index already existed")} else {console.log("the index has not been createdyet")client.helpers.bulk({datasource: [{ name: "Revelation Space", author: "Alastair Reynolds", release_date: "2000-03-15", page_count: 585 },{ name: "1984", author: "George Orwell", release_date: "1985-06-01", page_count: 328 },{ name: "Fahrenheit 451", author: "Ray Bradbury", release_date: "1953-10-15", page_count: 227 },{ name: "Brave New World", author: "Aldous Huxley", release_date: "1932-06-01", page_count: 268 },],onDocument(_doc) {return { index: { _index: "books" } }},})}})const response = await client.esql.query({ query: 'FROM books' })console.log(response)const query = 'FROM books | WHERE release_date > "1985-06-01" | LIMIT 5'const response1 = await client.esql.query({ query: query })console.log(response1)
}run().catch(console.log)上面最后一个查询的结果为：
