认识 Elasticsearch

ElasticSearch是一个基于Lucene的搜索服务器,它提供了一个分布式多用户能力的全文搜索引擎,基于RESTful web接口.Elasticsearch是用Java语言开发的, 并作为Apache许可条款下的开放源码发布,是一种流行的企业级搜索引擎．

安装elasticsearch

使用docker安装

拉取elasticsearch镜像

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sudo docker pull elasticsearch:6.4.0

修改vm.max_map_count参数

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sudo sysctl -w vm.max_map_count=262144

启动容器elasticsearch

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 sudo docker run -p 9200:9200 -p 9300:9300 --name elasticsearch \
 -e "discovery.type=single-node" \
 -e "cluster.name=elasticsearch" \
 -v /mydata/elasticsearch/plugins:/usr/share/elasticsearch/plugins \
 -v /mydata/elasticsearch/data:/usr/share/elasticsearch/data \
 -d elasticsearch:6.4.0

进入容器

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sudo docker exec -it elasticsearch /bin/bash

如果进入容器报错,修改数据文件权限,重启

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sudo chmod +777 /mydata/elasticsearch/data
sudo docker restart elasticsearch

测试是否启动成功

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curl  localhost:9200

基本概念

node和cluster

单个elasticsearch实例称为一个节点,一组节点构成为一个集群cluster

index(索引)

index是es数据管理的顶层单位,相当于mysql的数据库.在es中还有一个名词是倒序索引,关系型数据库通过增加一个索引比如一个 B树（B-tree）索引到指定的列上,以便提升数据检索速度.Elasticsearch 和 Lucene 使用了一个叫做倒排索引的结构来达到相同的目的. 默认的，一个文档中的每一个属性都是被索引的（有一个倒排索引）和可搜索的.一个没有倒排索引的属性是不能被搜索到的.

document(文档)

document是index里面存储的单条记录,同一个index里面不要求所有的document结构相同

和Elasticsearch进行交互

使用http请求的方式和elasticsearch进行交互

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curl -X<VERB> -H "Content-Type: application/json;charset=UTF-8" '<PROTOCOL>://<HOST>:<PORT>/<PATH>?<QUERY_STRING>' -d '<BODY>'

变量	含义
VERB	适当的 HTTP 方法或谓词 : GET、 POST、 PUT、 HEAD 或者 DELETE.
PROTOCOL	http 或者 https（如果你在 Elasticsearch 前面有一个 https 代理）
HOST	Elasticsearch 集群中任意节点的主机名,或者用 localhost 代表本地机器上的节点
PORT	运行 Elasticsearch HTTP 服务的端口号,默认是 9200
PATH	API 的终端路径（例如 _count 将返回集群中文档数量）。Path 可能包含多个组件,例如：_cluster/stats 和 _nodes/stats/jvm
QUERY_STRING	任意可选的查询字符串参数 (例如 ?pretty 将格式化地输出 JSON 返回值,使其更容易阅读)
BODY	一个 JSON 格式的请求体 (如果请求需要的话)

向索引中添加文档

向company索引中添加employee类型的文档.

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curl -XPUT -H "Content-Type:application/json;charset=UTF-8" http://localhost:9200/company/employee/1 -d '
{                         
    "first_name" : "John",
    "last_name" :  "Smith",
    "age" :        25,
    "about" :      "I love to go rock climbing",
    "interests": [ "sports", "music" ]
}'

company为索引的名称,employee为文档的类型,1为文档的id.

添加更多的employee

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curl -XPUT -H "Content-Type:application/json;charset=UTF-8" http://localhost:9200/company/employee/2 --d'
{
    "first_name" :  "Jane",
    "last_name" :   "Smith",
    "age" :         32,
    "about" :       "I like to collect rock albums",
    "interests":  [ "music" ]
}'

curl -XPUT -H "Content-Type:application/json;charset=UTF-8" http://localhost:9200/company/employee/3 --d '
{
    "first_name" :  "Douglas",
    "last_name" :   "Fir",
    "age" :         35,
    "about":        "I like to build cabinets",
    "interests":  [ "forestry" ]
}'

简单文档检索

查询id为1的employee

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curl http://localhost:9200/company/employee/1

返回结果:

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{"_index":"company","_type":"employee","_id":"1","_version":1,"found":true,"_source":
{
    "first_name" : "John",
    "last_name" :  "Smith",
    "age" :        25,
    "about" :      "I love to go rock climbing",
    "interests": [ "sports", "music" ]
}}

查询所有的employee

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curl http://localhost:9200/company/employee/_search?pretty

返回结果(一个搜索默认返回十条结果):

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{
  "took" : 1,
  "timed_out" : false,
  "_shards" : {
    "total" : 5,
    "successful" : 5,
    "skipped" : 0,
    "failed" : 0
  },
  "hits" : {
    "total" : 3,
    "max_score" : 1.0,
    "hits" : [
      {
        "_index" : "company",
        "_type" : "employee",
        "_id" : "2",
        "_score" : 1.0,
        "_source" : {
          "first_name" : "Jane",
          "last_name" : "Smith",
          "age" : 32,
          "about" : "I like to collect rock albums",
          "interests" : [
            "music"
          ]
        }
      },
      {
        "_index" : "company",
        "_type" : "employee",
        "_id" : "1",
        "_score" : 1.0,
        "_source" : {
          "first_name" : "John",
          "last_name" : "Smith",
          "age" : 25,
          "about" : "I love to go rock climbing",
          "interests" : [
            "sports",
            "music"
          ]
        }
      },
      {
        "_index" : "company",
        "_type" : "employee",
        "_id" : "3",
        "_score" : 1.0,
        "_source" : {
          "first_name" : "Douglas",
          "last_name" : "Fir",
          "age" : 35,
          "about" : "I like to build cabinets",
          "interests" : [
            "forestry"
          ]
        }
      }
    ]
  }
}

查询姓氏为Simth的雇员

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curl http://localhost:9200/company/employee/_search?q=last_name=Smith