ElasticSearch初探之基本概念和CRUD（二）

• 基本概念简介

index：索引，相当于关系数据库中的数据库database
type：类型，类似关系数据库中table
document：文档，相当于表中行记录row
field：列，相当于table中的colum
shard：分片，每个index包含多个shard，每个shard是保存数据的lucene实例。shard又分为：primary shard（ps） 和replica shard（rs），即主分片和副本分片，默认ps= 5，type中的每个document只能存在其中一个ps以及和它对应的rs中，ps和它对应的rs不能在同一个节点内（容错考虑）。

• 一个索引创建后，primary shard不可修改，但为了集群的高可用性和便于横向扩展replica shard可以动态修改。

[code]PUT /users/_settings
{
"number_of_replicas" : 10 //修改副本分片数
}

• 基本操作举例

es是完成基于RESTful web接口规范，以下基于rest风格举例
查看es状态

[code][root@Eden666 ~]# curl -XGET 'http://localhost:9200/_cluster/health?pretty'
{
"cluster_name" : "elasticsearch",
"status" : "yellow", //三种状态：green 完全可用，集群功能齐全，yellow：所有数据可用，但是有些副本尚未分配，red：部分数据有丢失
"timed_out" : false,
"number_of_nodes" : 1,
"number_of_data_nodes" : 1,
"active_primary_shards" : 5, //初始5个primary shard 分片
"active_shards" : 5,
"relocating_shards" : 0,
"initializing_shards" : 0,
"unassigned_shards" : 5,
"delayed_unassigned_shards" : 0,
"number_of_pending_tasks" : 0,
"number_of_in_flight_fetch" : 0,
"task_max_waiting_in_queue_millis" : 0,
"active_shards_percent_as_number" : 50.0
}

1、新增数据（POST），其中users就是index，coder是type，id就是field，若出现以下情况是因为es6.x版本需加入headers之Content-type(所有请求方式都一样)，详情可参考官网（https://www.elastic.co/blog/strict-content-type-checking-for-elasticsearch-rest-requests）

[code][root@Eden666 ~]# curl -XPOST  'localhost:9200/users/coder/3?pretty=true' -d '{"name":"eden03","age":10}'
{
"error" : "Content-Type header [application/x-www-form-urlencoded] is not supported",
"status" : 406
}
[root@Eden666 ~]# curl -H 'Content-type:application/json' -XPOST  'localhost:9200/users/coder/3?pretty=true' -d '{"name":"eden03","age":10}'
{
"_index" : "users",
"_type" : "coder",
"_id" : "3",
"_version" : 1,
"result" : "created",
"_shards" : {
"total" : 2,
"successful" : 1,
"failed" : 0
},
"_seq_no" : 3,
"_primary_term" : 2
}

2、修改（PUT）

[code][root@Eden666 ~]# curl -H 'Content-type:application/json' -XPUT  'localhost:9200/users/coder/3?pretty=true' -d '{"name":"eden03-new","age":100}'
{
"_index" : "users",
"_type" : "coder",
"_id" : "3",
"_version" : 2,
"result" : "updated",
"_shards" : {
"total" : 2,
"successful" : 1,
"failed" : 0
},
"_seq_no" : 4,
"_primary_term" : 2
}

3、查看（GET）

[code][root@Eden666 ~]# curl   -XGET  'localhost:9200/users/coder/3?pretty=true'
{
"_index" : "users",
"_type" : "coder",
"_id" : "3",
"_version" : 2,
"found" : true,
"_source" : {
"name" : "eden03-new",
"age" : 100
}
}

4、删除（DELETE），可以发现删除查询结果返回found=false

[code][root@Eden666 ~]# curl   -XDELETE  'localhost:9200/users/coder/3?pretty=true'
{
"_index" : "users",
"_type" : "coder",
"_id" : "3",
"_version" : 3,
"result" : "deleted",
"_shards" : {
"total" : 2,
"successful" : 1,
"failed" : 0
},
"_seq_no" : 5,
"_primary_term" : 2
}
[root@Eden666 ~]# curl localhost:9200/users/coder/3?pretty=true
{
"_index" : "users",
"_type" : "coder",
"_id" : "3",
"found" : false
}

5、其他检索方式，查询字符串方式和DSL(Domain Specific Language特定领域语言)方式

• 字符串查询：具有局限性，不够灵活

[code][root@Eden666 ~]# curl localhost:9200/users/coder/_search?pretty=true
{
"took" : 5,
"timed_out" : false,
"_shards" : {
"total" : 5,
"successful" : 5,
"skipped" : 0,
"failed" : 0
},
"hits" : {
"total" : 2,
"max_score" : 1.0,
"hits" : [
{
"_index" : "users",
"_type" : "coder",
"_id" : "2",
"_score" : 1.0,
"_source" : {
"name" : "eden02",
"age" : 30
}
},
{
"_index" : "users",
"_type" : "coder",
"_id" : "1",
"_score" : 1.0,
"_source" : {
"name" : "eden01",
"age" : 20
}
}
]
}
}
[root@Eden666 ~]#  curl  'localhost:9200/users/coder/_search?q=name:eden01&pretty'
{
"took" : 14,  //查询毫秒数
"timed_out" : false,
"_shards" : {
"total" : 5,
"successful" : 5,
"skipped" : 0,
"failed" : 0
},
"hits" : {
"total" : 1,
"max_score" : 0.2876821,
"hits" : [
{
"_index" : "users",
"_type" : "coder",
"_id" : "1",
"_score" : 0.2876821,  //检索的document的分数，分数越高越容易检索到
"_source" : {
"name" : "eden01",
"age" : 20
}
}
]
}
}

• DSL方式：可以建立复杂查询条件。match：匹配的字段值，size：指定返回document数，from：位移量，默认是0

[code][root@Eden666 ~]# curl -H "Content-Type:application/json"  -XGET 'localhost:9200/users/coder/_search?pretty' -d  '{"query":{"match":{"name":"eden02"}},"size":1,"from":0}'
{
"took" : 9,
"timed_out" : false,
"_shards" : {
"total" : 5,
"successful" : 5,
"skipped" : 0,
"failed" : 0
},
"hits" : {
"total" : 1,
"max_score" : 0.2876821,
"hits" : [
{
"_index" : "users",
"_type" : "coder",
"_id" : "2",
"_score" : 0.2876821,
"_source" : {
"name" : "eden02",
"age" : 30
}
}
]
}
}

• DSL查询之 or 和 and检索

[code]//or检索："query":{"match":{"name":"eden02 eden01"}}
[root@Eden666 ~]# curl -H "Content-Type:application/json"  -XGET 'localhost:9200/users/coder/_search?pretty' -d  '{"query":{"match":{"name":"eden02 eden01"}},"size":10,"from":0}'
{
"took" : 13,
"timed_out" : false,
"_shards" : {
"total" : 5,
"successful" : 5,
"skipped" : 0,
"failed" : 0
},
"hits" : {
"total" : 2,
"max_score" : 0.2876821,
"hits" : [
{
"_index" : "users",
"_type" : "coder",
"_id" : "2",
"_score" : 0.2876821,
"_source" : {
"name" : "eden02",
"age" : 30
}
},
{
"_index" : "users",
"_type" : "coder",
"_id" : "1",
"_score" : 0.2876821,
"_source" : {
"name" : "eden01",
"age" : 20
}
}
]
}
}
//and检索需使用到布尔查询
//{"bool": {"must": [ { "match": { "name": "eden01" } },{ "match": { "age": 20 } }]}}
[root@Eden666 ~]# curl -H "Content-Type:application/json"  -XGET 'localhost:9200/users/coder/_search?pretty' -d  '{"query":{"bool": {"must": [ { "match": { "name": "eden01" } },{ "match": { "age": 20 } }]}},"size":10,"from":0}'
{
"took" : 19,
"timed_out" : false,
"_shards" : {
"total" : 5,
"successful" : 5,
"skipped" : 0,
"failed" : 0
},
"hits" : {
"total" : 1,
"max_score" : 1.287682,
"hits" : [
{
"_index" : "users",
"_type" : "coder",
"_id" : "1",
"_score" : 1.287682,
"_source" : {
"name" : "eden01",
"age" : 20
}
}
]
}
}

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