elasticsearch的动态mappings

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以往我们在创建索引时会同时设置索引的mappings，然而对于elasticsearch来说，就算索引初次创建时未设置mappings，在用户直接插入数据时es会自动判断字段类型并设置mapping，从而达到一种动态设置mapping的效果，如果后续有新字段的引入，也会为新增字段增加mappIngs。

有个点不要搞混了，就是mappings中的字段一旦配置了，那么字段的mappings将不可再改变，比如某字段type以设置为keyword，则以后都不能更改为其他type，只能reindex来重建。和此处讲的动态mappings不是一个事！！！！此处动态仅仅是对字段自动新建相应的mappings。

动态创建mappings

# 向一个不存在的索引插入数据
PUT test_mappings/_doc/1
{
  "message":"德玛西亚大宝剑"
}

查看自动创建的索引的配置信息

# 查看该索引配置
GET test_mappings

# 输出
{
  "test_mappings" : {
    "aliases" : { },
    "mappings" : {
      "properties" : {
        "message" : {
          "type" : "text",
          "fields" : {
            "keyword" : {
              "type" : "keyword",
              "ignore_above" : 256
            }
          }
        }
      }
    },
    "settings" : {
      "index" : {
        "creation_date" : "1593880162297",
        "number_of_shards" : "1",
        "number_of_replicas" : "1",
        "uuid" : "EjGl-PCBTqOhPv-vTgtOHQ",
        "version" : {
          "created" : "7070099"
        },
        "provided_name" : "test_mappings"
      }
    }
  }
}

从上面我们可以看到该索引已经自动为message该字段设置了mappings，此时我们再插入第二条数据，同时增加一个字段

PUT test_mappings/_doc/2
{
  "message":"啦啦啦德玛西亚",
    "count": 23
}

# 再次查看该索引配置
{
  "test_mappings" : {
    "aliases" : { },
    "mappings" : {
      "properties" : {
        "count" : {
          "type" : "long"
        },
        "message" : {
          "type" : "text",
          "fields" : {
            "keyword" : {
              "type" : "keyword",
              "ignore_above" : 256
            }
          }
        }
      }
    },
    "settings" : {
      "index" : {
        "creation_date" : "1593880162297",
        "number_of_shards" : "1",
        "number_of_replicas" : "1",
        "uuid" : "EjGl-PCBTqOhPv-vTgtOHQ",
        "version" : {
          "created" : "7070099"
        },
        "provided_name" : "test_mappings"
      }
    }
  }
}

从上面的例子中可以看到elasticsearch会为新增的字段根据类型自动设置mappings，这是es的默认配置。我们可以通过dynamic这个属性控制，其值有：

• true：缺省值，动态添加新字段映射
• false：忽略新字段映射创建，但是新字段数据依然能插入，只是根据该新字段查询是会查不到数据的，但是会在查询结果中显示（根据已存在mapping字段的查询结果）
• strict：遇到新字段，直接抛出异常

关闭动态mappings

# 创建索引时关闭动态创建索引
PUT test_mappings2
{
  "mappings": {
    "dynamic":false,
    "properties": {
      "message":{
        "type": "text"
      }
    }
  }
}

插入数据测试下

PUT test_mappings2/_doc/1
{
  "message":"啦啦啦德玛西亚"
}
PUT test_mappings2/_doc/2
{
  "message":"啦啦啦德玛西亚",
  "count": 23
}
GET test_mappings2/_search
{
  "query": {
    "match": {
      "count": "23"
    }
  }
}

# 获取到的输出
{
  "took" : 36,
  "timed_out" : false,
  "_shards" : {
    "total" : 1,
    "successful" : 1,
    "skipped" : 0,
    "failed" : 0
  },
  "hits" : {
    "total" : {
      "value" : 0,
      "relation" : "eq"
    },
    "max_score" : null,
    "hits" : [ ]
  }
}

查询其他字段时

GET test_mappings2/_search
{
  "query": {
    "match": {
      "message": "德玛"
    }
  }
}

# 输出
{
  "took" : 101,
  "timed_out" : false,
  "_shards" : {
    "total" : 1,
    "successful" : 1,
    "skipped" : 0,
    "failed" : 0
  },
  "hits" : {
    "total" : {
      "value" : 2,
      "relation" : "eq"
    },
    "max_score" : 0.21072102,
    "hits" : [
      {
        "_index" : "test_mappings2",
        "_type" : "_doc",
        "_id" : "2",
        "_score" : 0.21072102,
        "_source" : {
          "message" : "啦啦啦德玛西亚",
          "count" : 23
        }
      },
      {
        "_index" : "test_mappings2",
        "_type" : "_doc",
        "_id" : "1",
        "_score" : 0.21072102,
        "_source" : {
          "message" : "啦啦啦德玛西亚"
        }
      }
    ]
  }
}

将mappings设置为严格模式

PUT test_mappings3
{
  "mappings": {
    "dynamic": "strict",
    "properties": {
      "message":{
        "type": "text"
      }
    }
  }
}
PUT test_mappings3/_doc/1
{
  "message":"啦啦啦德玛西亚"
}

# 插入数据成功，输出:
{
  "_index" : "test_mappings3",
  "_type" : "_doc",
  "_id" : "1",
  "_version" : 1,
  "result" : "created",
  "_shards" : {
    "total" : 2,
    "successful" : 2,
    "failed" : 0
  },
  "_seq_no" : 0,
  "_primary_term" : 1
}

测试插入新字段数据

PUT test_mappings3/_doc/2
{
  "message":"啦啦啦德玛西亚",
  "count": 2333
}

# 输出
{
  "error" : {
    "root_cause" : [
      {
        "type" : "strict_dynamic_mapping_exception",
        "reason" : "mapping set to strict, dynamic introduction of [count] within [_doc] is not allowed"
      }
    ],
    "type" : "strict_dynamic_mapping_exception",
    "reason" : "mapping set to strict, dynamic introduction of [count] within [_doc] is not allowed"
  },
  "status" : 400
}