1.索引

目的：存储学生的分数信息，且支持 搜索 “姓名、课程名、分数”

--  示例数据 --  {"username":"zs","courses": [{"course":"数学","grade": 99},{"course":"英语","grade": 88}]}

1.1 创建索引

1.1.1 自动创建索引

put 数据时，es会自动创建索引（不推荐）

1.1.2 手动创建索引

user_course 为索引名

# 创建新索引
PUT /user_course
{"mappings": {"properties": {"name": {"type": "text","fields": {"keyword": {"type": "keyword"}}},"courses": {"type": "nested","properties": {"course": {"type": "text","fields": {"keyword": {"type": "keyword"}}},"grade": {"type": "text","fields": {"keyword": {"type": "keyword"}}}}}}}
} 

courses 使用 nested ， 支持 course=“数学” && grade>=98的查询
nested的作用，参考后续章节

1.2 删除索引

 DELETE /user_course

1.3 查看索引

     GET /user_course/_mapping

1.4 修改索引

1.4.1 创建新索引

PUT /user_course_new_index
{"mappings": {"name": {"type": "text","fields": {"keyword": {"type": "keyword","ignore_above": 256}}},"properties": {"courses": {"type":"nested","properties": {"course": {"type": "text","fields": {"keyword": {"type": "keyword","ignore_above": 256}}},"grade": {"type": "text","fields": {"keyword": {"type": "keyword","ignore_above": 256}}}}}}}
} 

1.4.2 迁移数据

POST _reindex
{"source": {"index": "user_course"},"dest": {"index": "user_course_new_index"}
}

1.4.3 将对外访问的别名设置到新的 索引

POST /_aliases
{"actions": [{"add": {"index": "user_course_new_index","alias": "my_alias"}}]
}

对外提供别名访问的好处：ES内部可以修改索引，对外0感知