Elasticsearch学习之快速入门案例

1. document数据格式

面向文档的搜索分析引擎

（1）应用系统的数据结构都是面向对象的，复杂的
（2）对象数据存储到数据库中，只能拆解开来，变为扁平的多张表，每次查询的时候还得还原回对象格式，相当麻烦
（3）ES是面向文档的，文档中存储的数据结构，与面向对象的数据结构是一样的，基于这种文档数据结构，es可以提供复杂的索引，全文检索，分析聚合等功能
（4）es的document用json数据格式来表达

 public class Employee {

   private String email;
   private String firstName;
   private String lastName;
   private EmployeeInfo info;
   private Date joinDate;

 }

 private class EmployeeInfo {

   private String bio; // 性格
   private Integer age;
   private String[] interests; // 兴趣爱好

 }

 EmployeeInfo info = new EmployeeInfo();
 info.setBio("curious and modest");
 info.setAge();
 info.setInterests(new String[]{"bike", "climb"});

 Employee employee = new Employee();
 employee.setEmail("zhangsan@sina.com");
 employee.setFirstName("san");
 employee.setLastName("zhang");
 employee.setInfo(info);
 employee.setJoinDate(new Date());

 employee对象：里面包含了Employee类自己的属性，还有一个EmployeeInfo对象

两张表：employee表，employee_info表，将employee对象的数据重新拆开来，变成Employee数据和EmployeeInfo数据
employee表：email，first_name，last_name，join_date，4个字段
employee_info表：bio，age，interests，3个字段；此外还有一个外键字段，比如employee_id，关联着employee表

{
    "email":      "zhangsan@sina.com",
    "first_name": "san",
    "last_name": "zhang",
    "info": {
        "bio":         "curious and modest",
        "age":         ,
        "interests": [ "bike", "climb" ]
    },
    "join_date": "2017/01/01"
}

我们就明白了es的document数据格式和数据库的关系型数据格式的区别

2. 电商网站商品管理案例

有一个电商网站，需要为其基于ES构建一个后台系统，提供以下功能：

（1）对商品信息进行CRUD（增删改查）操作
（2）执行简单的结构化查询
（3）可以执行简单的全文检索，以及复杂的phrase（短语）检索
（4）对于全文检索的结果，可以进行高亮显示
（5）对数据进行简单的聚合分析

3. 简单的集群管理

（1）快速检查集群的健康状况

es提供了一套api，叫做cat api，可以查看es中各种各样的数据

GET /_cat/health?v

epoch      timestamp cluster       status node.total node.data shards pri relo init unassign pending_tasks max_task_wait_time active_shards_percent
 ::  elasticsearch yellow                                                                           -                 50.0%

epoch      timestamp cluster       status node.total node.data shards pri relo init unassign pending_tasks max_task_wait_time active_shards_percent
 ::  elasticsearch green                                                                            -                100.0%

epoch      timestamp cluster       status node.total node.data shards pri relo init unassign pending_tasks max_task_wait_time active_shards_percent
 ::  elasticsearch yellow                                                                           -                 50.0%

如何快速了解集群的健康状况？green、yellow、red？

　　green：每个索引的primary shard和replica shard都是active状态的
　　yellow：每个索引的primary shard都是active状态的，但是部分replica shard不是active状态，处于不可用的状态
　　red：不是所有索引的primary shard都是active状态的，部分索引有数据丢失了

为什么现在会处于一个yellow状态？

　　我们现在就一个笔记本电脑，就启动了一个es进程，相当于就只有一个node。现在es中有一个index，就是kibana自己内置建立的index。由于默认的配置是给每个index分配5个primary shard和5个replica shard，而且primary shard和replica shard不能在同一台机器上（为了容错）。现在kibana自己建立的index是1个primary shard和1个replica shard。当前就一个node，所以只有1个primary shard被分配了和启动了，但是一个replica shard没有第二台机器去启动。做一个小实验：此时只要启动第二个es进程，就会在es集群中有2个node，然后那1个replica shard就会自动分配过去，然后cluster status就会变成green状态。

（2）快速查看集群中有哪些索引

GET /_cat/indices?v

health status index   uuid                   pri rep docs.count docs.deleted store.size pri.store.size
yellow open   .kibana rUm9n9wMRQCCrRDEhqneBg                                  .1kb          .1kb

（3）简单的索引操作

创建索引：PUT /test_index?pretty

health status index      uuid                   pri rep docs.count docs.deleted store.size pri.store.size
yellow open   test_index XmS9DTAtSkSZSwWhhGEKkQ                                   650b           650b
yellow open   .kibana    rUm9n9wMRQCCrRDEhqneBg                                  .1kb          .1kb
删除索引：DELETE /test_index?pretty

　health status index uuid pri rep docs.count docs.deleted store.size pri.store.size
  yellow open .kibana rUm9n9wMRQCCrRDEhqneBg 1 1 1 0 3.1kb 3.1kb

4. 商品的CRUD操作

（1）新增商品：新增文档，建立索引

PUT /index/type/id
{
  "json数据"
}

PUT /ecommerce/product/
{
    "name" : "gaolujie yagao",
    "desc" :  "gaoxiao meibai",
    "price" :  ,
    "producer" :      "gaolujie producer",
    "tags": [ "meibai", "fangzhu" ]
}

{
  "_index": "ecommerce",
  "_type": "product",
  "_id": "",
  "_version": ,
  "result": "created",
  "_shards": {
    "total": ,
    "successful": ,
    "failed":
  },
  "created": true
}

PUT /ecommerce/product/
{
    "name" : "jiajieshi yagao",
    "desc" :  "youxiao fangzhu",
    "price" :  ,
    "producer" :      "jiajieshi producer",
    "tags": [ "fangzhu" ]
}

PUT /ecommerce/product/
{
    "name" : "zhonghua yagao",
    "desc" :  "caoben zhiwu",
    "price" :  ,
    "producer" :      "zhonghua producer",
    "tags": [ "qingxin" ]
}

es会自动建立index和type，不需要提前创建，而且es默认会对document每个field都建立倒排索引，让其可以被搜索

（2）查询商品：检索文档

GET /index/type/id
GET /ecommerce/product/

{
  "_index": "ecommerce",
  "_type": "product",
  "_id": "",
  "_version": ,
  "found": true,
  "_source": {
    "name": "gaolujie yagao",
    "desc": "gaoxiao meibai",
    "price": ,
    "producer": "gaolujie producer",
    "tags": [
      "meibai",
      "fangzhu"
    ]
  }
}

（3）修改商品：替换文档

PUT /ecommerce/product/
{
    "name" : "jiaqiangban gaolujie yagao",
    "desc" :  "gaoxiao meibai",
    "price" :  ,
    "producer" :      "gaolujie producer",
    "tags": [ "meibai", "fangzhu" ]
}

{
  "_index": "ecommerce",
  "_type": "product",
  "_id": "",
  "_version": ,
  "result": "created",
  "_shards": {
    "total": ,
    "successful": ,
    "failed":
  },
  "created": true
}

{
  "_index": "ecommerce",
  "_type": "product",
  "_id": "",
  "_version": ,
  "result": "updated",
  "_shards": {
    "total": ,
    "successful": ,
    "failed":
  },
  "created": false
}

PUT /ecommerce/product/
{
    "name" : "jiaqiangban gaolujie yagao"
}

替换方式有一个不好，即使必须带上所有的field，才能去进行信息的修改

（4）修改商品：更新文档

POST /ecommerce/product//_update
{
  "doc": {
    "name": "jiaqiangban gaolujie yagao"
  }
}

{
  "_index": "ecommerce",
  "_type": "product",
  "_id": "",
  "_version": ,
  "result": "updated",
  "_shards": {
    "total": ,
    "successful": ,
    "failed":
  }
}

（5）删除商品：删除文档

DELETE /ecommerce/product/

{
  "found": true,
  "_index": "ecommerce",
  "_type": "product",
  "_id": "",
  "_version": ,
  "result": "deleted",
  "_shards": {
    "total": ,
    "successful": ,
    "failed":
  }
}

{
  "_index": "ecommerce",
  "_type": "product",
  "_id": "",
  "found": false
}