ElasticSearch系列——用个例子告诉你mapping到底是什么

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ElasticSearch系列——主目录

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插入几条数据，让es自动为我们建立一个索引

PUT /website/article/1
{
  "post_date": "2017-01-01",
  "title": "my first article",
  "content": "this is my first article in this website",
  "author_id": 11400
}

PUT /website/article/2
{
  "post_date": "2017-01-02",
  "title": "my second article",
  "content": "this is my second article in this website",
  "author_id": 11400
}

PUT /website/article/3
{
  "post_date": "2017-01-03",
  "title": "my third article",
  "content": "this is my third article in this website",
  "author_id": 11400
}

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mapping

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自动或手动为index中的type建立的一种数据结构和相关配置，简称为mapping

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dynamic mapping

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dynamic mapping，自动为我们建立index，创建type，以及type对应的mapping，mapping中包含了每个field对应的数据类型，以及如何分词等设置

GET /website/_mapping/article

{
  "website": {
    "mappings": {
      "article": {
        "properties": {
          "author_id": {
            "type": "long"
          },
          "content": {
            "type": "text",
            "fields": {
              "keyword": {
                "type": "keyword",
                "ignore_above": 256
              }
            }
          },
          "post_date": {
            "type": "date"
          },
          "title": {
            "type": "text",
            "fields": {
              "keyword": {
                "type": "keyword",
                "ignore_above": 256
              }
            }
          }
        }
      }
    }
  }
}

尝试各种搜索

GET /website/article/_search?q=2017			3条结果    

搜索的是_all field，document所有的field都会拼接成一个大串，进行分词

2017-01-02 my second article this is my second article in this website 11400

		  doc1	  doc2	  doc3
2017		*		*		*
01			* 		
02					*
03							*

_all，2017，自然会搜索到3个docuemnt


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GET /website/article/_search?q=2017-01-01        	3条结果


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GET /website/article/_search?q=post_date:2017-01-01   	1条结果

post_date，会作为exact value去建立索引

		doc1		doc2		doc3
2017-01-01	*		
2017-01-02			* 		
2017-01-03					*

post_date:2017-01-01，2017-01-01，doc1一条document


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GET /website/article/_search?q=post_date:2017         	1条结果

搜索结果为什么不一致，因为es自动建立mapping的时候，设置了不同的field不同的data type。不同的data type的分词、搜索等行为是不一样的。所以出现了_all field和post_date field的搜索表现完全不一样。

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mapping数据底层结构

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{
  "address": {
    "country": "china",
    "province": "guangdong",
    "city": "guangzhou"
  },
  "name": "jack",
  "age": 27,
  "join_date": "2017-01-01"
}


底层
{
    "name":            [jack],
    "age":          [27],
    "join_date":      [2017-01-01],
    "address.country":         [china],
    "address.province":   [guangdong],
    "address.city":  [guangzhou]
}

{
    "authors": [
        { "age": 26, "name": "Jack White"},
        { "age": 55, "name": "Tom Jones"},
        { "age": 39, "name": "Kitty Smith"}
    ]
}


底层
{
    "authors.age":    [26, 55, 39],
    "authors.name":   [jack, white, tom, jones, kitty, smith]
}