Elasticsearch學習筆記之文檔的增刪改查

Elasticsearch相關概念講解，參看官方博客 ，可以看下這篇文章對Elasticsearch來個初步印象：《終於有人把Elasticsearch原理講透了》。

筆記參考：

官方博客：開始使用Elasticsearch (1)

假設我們已經安裝好Elasticsearch和Kibana,瀏覽器輸入ip:5601，進入Kibana操作界面，這次我們使用到的是Kibana菜單裏的Dev Tools功能。

創建文檔

執行如下命令：

POST twitter/_doc/1
{
    "username":"Dannis",
    "uid":1
}

這行命令表明，向Elasticsearch發送一個POST請求，創建一個名爲twitter的索引（index），同時生成一個文檔，文檔的ID爲1，點擊三角圖標執行請求。

生成結果爲：

{
  "_index" : "twitter",
  "_type" : "_doc",
  "_id" : "1",
  "_version" : 1,
  "result" : "created",
  "_shards" : {
    "total" : 2,
    "successful" : 1,
    "failed" : 0
  },
  "_seq_no" : 0,
  "_primary_term" : 1
}

我們來分析下返回的結果信息，_index表明我們創建的索引名爲twitter，_type類型是文檔類型_doc，_id文檔ID爲1，這些信息都是我們在請求裏指定的，沒問題，接下來，version表示版本號，result表明我們的操作屬於創建created，_shards表示分片信息，裏面的信息表明有2個分片，成功1個，失敗0個，這是什麼意思呢？

我們執行GET _cat/shards/twitter命令，該命令是用來查看索引的分片信息，輸出結果如下所示：

twitter 0 p STARTED    1 3.8kb 172.29.0.2 09baeea2d96a
twitter 0 r UNASSIGNED     

我們看到創建的索引twitter有兩個分片，p是primary的首字母縮寫，表示主分片，STAARTED表示分片正常。r又是什麼呢？

我們再來看下索引的設置信息setting，輸入並執行：

GET twitter/_settings

返回結果如下：

{
  "twitter" : {
    "settings" : {
      "index" : {
        "creation_date" : "1591930378288",
        "number_of_shards" : "1",
        "number_of_replicas" : "1",
        "uuid" : "3vc_AZQcQbGM-a6FtTSX5g",
        "version" : {
          "created" : "7070199"
        },
        "provided_name" : "twitter"
      }
    }
  }
}

可以看到索引的詳細信息，creation_date表示索引的創建時間，以時間戳形式展示；number_of_shards表示主分片的數量，默認是1，number_of_replicas表示索引的副本數量，默認也是1。

回到上面GET _cat/shards/twitter命令的返回結果，我們知道了r 表示的是分片副本的意思，即replica的首字母，UNASSIGNED意爲未分配，爲什麼是這個呢？這是因爲我本地環境開啓的的Elasticsearch環境爲開發模式，只有一個節點，也就是主節點，如果開啓的是集羣模式，則副本數據則會自動分配到加入的節點上。

創建文檔的時候，如果沒有指定文檔ID，Elasticsearch會自動給該文檔生成一個ID，如下：

POST twitter/_doc
{
  "username":"test",
  "age":20
}

返回結果：

{
  "_index" : "twitter",
  "_type" : "_doc",
  "_id" : "EIcep3IBFDGGZnEIs9aT",
  "_version" : 1,
  "result" : "created",
  "_shards" : {
    "total" : 2,
    "successful" : 1,
    "failed" : 0
  },
  "_seq_no" : 4,
  "_primary_term" : 1
}

我們看到返回有將文檔_id返回，再來查看一下：

GET twitter/_doc/EIcep3IBFDGGZnEIs9aT

返回內容正是我們期望寫入的數據：

{
  "_index" : "twitter",
  "_type" : "_doc",
  "_id" : "EIcep3IBFDGGZnEIs9aT",
  "_version" : 1,
  "_seq_no" : 4,
  "_primary_term" : 1,
  "found" : true,
  "_source" : {
    "username" : "test",
    "age" : 20
  }
}

我們還可以通過調用_create方法來創建文檔，如下：

POST twitter/_create/2
{
  "username":"GB",
  "uid":1,
  "city":"Guangzhou",
  "province":"Guangdong",
  "country":"China"
}

返回結果：

{
  "_index" : "twitter",
  "_type" : "_doc",
  "_id" : "2",
  "_version" : 1,
  "result" : "created",
  "_shards" : {
    "total" : 2,
    "successful" : 1,
    "failed" : 0
  },
  "_seq_no" : 6,
  "_primary_term" : 1
}

可知數據已成功寫入，如果我們再次調用如下命令:

POST twitter/_create/2
{
  "username":"GB",
  "uid":1,
  "city":"Guangzhou",
  "province":"Guangdong",
  "country":"China"
}

返回結果如下：

{
  "error" : {
    "root_cause" : [
      {
        "type" : "version_conflict_engine_exception",
        "reason" : "[2]: version conflict, document already exists (current version [1])",
        "index_uuid" : "AiRNBupCRWWLFKqFSVW3mw",
        "shard" : "0",
        "index" : "twitter"
      }
    ],
    "type" : "version_conflict_engine_exception",
    "reason" : "[2]: version conflict, document already exists (current version [1])",
    "index_uuid" : "AiRNBupCRWWLFKqFSVW3mw",
    "shard" : "0",
    "index" : "twitter"
  },
  "status" : 409
}

返回錯誤，提示我們文檔已經存在，那麼如果執行下面的命令呢？

POST twitter/_doc/1
{
  "username":"Dannis",
  "uid":1
}

返回結果如下：

{
  "_index" : "twitter",
  "_type" : "_doc",
  "_id" : "1",
  "_version" : 2,
  "result" : "updated",
  "_shards" : {
    "total" : 2,
    "successful" : 1,
    "failed" : 0
  },
  "_seq_no" : 7,
  "_primary_term" : 1
}

發現成功響應，只是result值變成了updated,並且版本號也變成了2，由此可知，如果使用POST twitter/_create/2方式來創建文檔，只有該文檔ID不存在才能創建成功，使用POST twitter/_doc/1方式來創建文檔，如果文檔不存在，則創建，如果文檔已存在，則結果會變成對指定文檔的更新操作，並且版本號加1。

查詢文檔

輸入執行：

GET twitter/_doc/1

返回結果：

{
  "_index" : "twitter",
  "_type" : "_doc",
  "_id" : "1",
  "_version" : 1,
  "_seq_no" : 0,
  "_primary_term" : 1,
  "found" : true,
  "_source" : {
    "username" : "Dannis",
    "uid" : 1
  }
}

可以看到我們定義的文檔數據被放在了_source字段下面，found字段表示查到了該文檔，如果我們輸入以下命令：

GET twitter/_doc/2

返回結果:

{
  "_index" : "twitter",
  "_type" : "_doc",
  "_id" : "2",
  "found" : false
}

可以看到found爲false。

修改文檔

輸入命令並執行：

POST twitter/_update/1
{
  "doc": {
    "username":"Dannis-update"
  }
}

返回結果：

{
  "_index" : "twitter",
  "_type" : "_doc",
  "_id" : "1",
  "_version" : 2,
  "result" : "updated",
  "_shards" : {
    "total" : 2,
    "successful" : 1,
    "failed" : 0
  },
  "_seq_no" : 1,
  "_primary_term" : 1
}

我們看到result值變成了updated，_version也變成了2，再查看一下：

GET twitter/_doc/1

返回結果：

{
  "_index" : "twitter",
  "_type" : "_doc",
  "_id" : "1",
  "_version" : 2,
  "_seq_no" : 1,
  "_primary_term" : 1,
  "found" : true,
  "_source" : {
    "username" : "Dannis-update",
    "uid" : 1
  }
}

沒問題，username已變成了我們想要的。

如果我們更新的時候是加入一個不存在的字段，看下發生什麼？輸入以下命令並執行：

POST twitter/_update/1
{
  "doc": {
    "age":25
  }
}

返回結果：

{
  "_index" : "twitter",
  "_type" : "_doc",
  "_id" : "1",
  "_version" : 3,
  "result" : "updated",
  "_shards" : {
    "total" : 2,
    "successful" : 1,
    "failed" : 0
  },
  "_seq_no" : 2,
  "_primary_term" : 1
}

可以看到文檔的版本號變爲3了。

再來查看一下，

GET twitter/_doc/1

返回結果：

{
  "_index" : "twitter",
  "_type" : "_doc",
  "_id" : "1",
  "_version" : 3,
  "_seq_no" : 2,
  "_primary_term" : 1,
  "found" : true,
  "_source" : {
    "username" : "Dannis-update",
    "uid" : 1,
    "age" : 25
  }
}

發現返回的_source裏也包含了剛加的內容，由此可知，如果字段存在，則會更新原來的字段內容，如果字段不存在，則會添加新的字段內容。

刪除文檔

輸入命令並執行：

DELETE twitter/_doc/1

返回結果：

{
  "_index" : "twitter",
  "_type" : "_doc",
  "_id" : "1",
  "_version" : 4,
  "result" : "deleted",
  "_shards" : {
    "total" : 2,
    "successful" : 1,
    "failed" : 0
  },
  "_seq_no" : 3,
  "_primary_term" : 1
}

可看到_version變成了4，而result爲deleted，由此發現，我們對文檔每進行一次寫入/更新操作，版本號都會加1。

我們再來查看一下：

GET twitter/_doc/1

返回結果：

{
  "_index" : "twitter",
  "_type" : "_doc",
  "_id" : "1",
  "found" : false
}

found爲false，表示找不到ID爲1的文檔了，表明刪除文檔成功。

下面來看下對文檔的批量操作。

批量創建文檔

批量創建多個文檔，輸入以下命令並執行：

POST _bulk
{"index":{"_index":"twitter","_id":3}}
{"username":"張三","uid":3,"age":30}
{"index":{"_index":"twitter","_id":4}}
{"username":"李四","uid":4,"age":25}
{"index":{"_index":"twitter","_id":5}}
{"username":"王五","uid":5,"age":18}

返回結果：

{
  "took" : 44,
  "errors" : false,
  "items" : [
    {
      "index" : {
        "_index" : "twitter",
        "_type" : "_doc",
        "_id" : "3",
        "_version" : 1,
        "result" : "created",
        "_shards" : {
          "total" : 2,
          "successful" : 1,
          "failed" : 0
        },
        "_seq_no" : 9,
        "_primary_term" : 1,
        "status" : 201
      }
    },
    {
      "index" : {
        "_index" : "twitter",
        "_type" : "_doc",
        "_id" : "4",
        "_version" : 1,
        "result" : "created",
        "_shards" : {
          "total" : 2,
          "successful" : 1,
          "failed" : 0
        },
        "_seq_no" : 10,
        "_primary_term" : 1,
        "status" : 201
      }
    },
    {
      "index" : {
        "_index" : "twitter",
        "_type" : "_doc",
        "_id" : "5",
        "_version" : 1,
        "result" : "created",
        "_shards" : {
          "total" : 2,
          "successful" : 1,
          "failed" : 0
        },
        "_seq_no" : 11,
        "_primary_term" : 1,
        "status" : 201
      }
    }
  ]
}

沒有異常，如果我們想同時往不同的索引裏寫入數據呢？執行以下命令：

POST _bulk
{"index":{"_index":"twitter","_id":6}}
{"username":"Jack","uid":6,"age":22}
{"index":{"_index":"twitter_v1","_id":1}}
{"username":"test","age":20}

我們同時往twitter和twitter_v1各寫入一條數據，分別用GET twitter/_doc/6和GET twitter_v1/_doc/1查詢，都能正常查詢到。

批量查詢文檔

如果我們想同時查詢多個文檔，可執行如下命令：

GET _mget
{
  "docs":[
    {
      "_index":"twitter",
      "_id":1
    },
    {
      "_index":"twitter",
      "_id":2
    }
  ]
}

返回結果：

{
  "docs" : [
    {
      "_index" : "twitter",
      "_type" : "_doc",
      "_id" : "1",
      "_version" : 3,
      "_seq_no" : 8,
      "_primary_term" : 1,
      "found" : true,
      "_source" : {
        "username" : "GB",
        "uid" : 1,
        "city" : "Guangzhou2",
        "province" : "Guangdong",
        "country" : "China"
      }
    },
    {
      "_index" : "twitter",
      "_type" : "_doc",
      "_id" : "2",
      "_version" : 1,
      "_seq_no" : 6,
      "_primary_term" : 1,
      "found" : true,
      "_source" : {
        "username" : "GB",
        "uid" : 1,
        "city" : "Guangzhou",
        "province" : "Guangdong",
        "country" : "China"
      }
    }
  ]
}

這是同時查同一個索引的文檔，也可以同時查多個索引下的文檔，比如：

GET _mget
{
  "docs":[
    {
      "_index":"twitter",
      "_id":1
    },
    {
      "_index":"twitter_v1",
      "_id":1
    }
  ]
}

結果如下：

{
  "docs" : [
    {
      "_index" : "twitter",
      "_type" : "_doc",
      "_id" : "1",
      "_version" : 3,
      "_seq_no" : 8,
      "_primary_term" : 1,
      "found" : true,
      "_source" : {
        "username" : "GB",
        "uid" : 1,
        "city" : "Guangzhou2",
        "province" : "Guangdong",
        "country" : "China"
      }
    },
    {
      "_index" : "twitter_v1",
      "_type" : "_doc",
      "_id" : "1",
      "_version" : 1,
      "_seq_no" : 0,
      "_primary_term" : 1,
      "found" : true,
      "_source" : {
        "username" : "test",
        "age" : 20
      }
    }
  ]
}

批量更新文檔

批量更新文檔，執行如下命令：

POST _bulk
{"update":{"_index":"twitter","_id":1}}
{"doc":{"username":"GB-update"}}
{"update":{"_index":"twitter_v1","_id":1}}
{"doc":{"age":25}}

返回結果：

{
  "took" : 107,
  "errors" : false,
  "items" : [
    {
      "update" : {
        "_index" : "twitter",
        "_type" : "_doc",
        "_id" : "1",
        "_version" : 4,
        "result" : "updated",
        "_shards" : {
          "total" : 2,
          "successful" : 1,
          "failed" : 0
        },
        "_seq_no" : 13,
        "_primary_term" : 1,
        "status" : 200
      }
    },
    {
      "update" : {
        "_index" : "twitter_v1",
        "_type" : "_doc",
        "_id" : "1",
        "_version" : 2,
        "result" : "updated",
        "_shards" : {
          "total" : 2,
          "successful" : 1,
          "failed" : 0
        },
        "_seq_no" : 1,
        "_primary_term" : 1,
        "status" : 200
      }
    }
  ]
}

我們再用以下命令查詢一下：

GET _mget
{
  "docs":[
    {
      "_index":"twitter",
      "_id":1
    },
    {
      "_index":"twitter_v1",
      "_id":1
    }
  ]
}

返回結果如下所示，發現數據都變成了我們想要的內容。

{
  "docs" : [
    {
      "_index" : "twitter",
      "_type" : "_doc",
      "_id" : "1",
      "_version" : 4,
      "_seq_no" : 13,
      "_primary_term" : 1,
      "found" : true,
      "_source" : {
        "username" : "GB-update",
        "uid" : 1,
        "city" : "Guangzhou2",
        "province" : "Guangdong",
        "country" : "China"
      }
    },
    {
      "_index" : "twitter_v1",
      "_type" : "_doc",
      "_id" : "1",
      "_version" : 2,
      "_seq_no" : 1,
      "_primary_term" : 1,
      "found" : true,
      "_source" : {
        "username" : "test",
        "age" : 25
      }
    }
  ]
}

批量刪除文檔

批量刪除文檔跟批量更新的命令類似，如下：

POST _bulk
{"delete":{"_index":"twitter","_id":1}}
{"delete":{"_index":"twitter_v1","_id":1}}

返回結果：

{
  "took" : 80,
  "errors" : false,
  "items" : [
    {
      "delete" : {
        "_index" : "twitter",
        "_type" : "_doc",
        "_id" : "1",
        "_version" : 5,
        "result" : "deleted",
        "_shards" : {
          "total" : 2,
          "successful" : 1,
          "failed" : 0
        },
        "_seq_no" : 14,
        "_primary_term" : 1,
        "status" : 200
      }
    },
    {
      "delete" : {
        "_index" : "twitter_v1",
        "_type" : "_doc",
        "_id" : "1",
        "_version" : 3,
        "result" : "deleted",
        "_shards" : {
          "total" : 2,
          "successful" : 1,
          "failed" : 0
        },
        "_seq_no" : 2,
        "_primary_term" : 1,
        "status" : 200
      }
    }
  ]
}

我們再用GET _mget命令去查這兩個文檔的時候，發現是找不到數據了，返回結果如下：

{
  "docs" : [
    {
      "_index" : "twitter",
      "_type" : "_doc",
      "_id" : "1",
      "found" : false
    },
    {
      "_index" : "twitter_v1",
      "_type" : "_doc",
      "_id" : "1",
      "found" : false
    }
  ]
}

同時進行創建、更新、刪除文檔操作

通過上面的例子我們發現，對文檔的批量操作都是通過_bulk命令來操作，只是傳入的參數不同，那麼可不可以同時進行創建、更新、刪除操作呢？試一下：

POST _bulk
{"index":{"_index":"twitter","_id":10}}
{"username":"小飛飛","age":12}
{"update":{"_index":"twitter","_id":3}}
{"doc":{"username":"張三-update"}}
{"delete":{"_index":"twitter","_id":6}}

返回結果：

{
  "took" : 51,
  "errors" : false,
  "items" : [
    {
      "index" : {
        "_index" : "twitter",
        "_type" : "_doc",
        "_id" : "10",
        "_version" : 1,
        "result" : "created",
        "_shards" : {
          "total" : 2,
          "successful" : 1,
          "failed" : 0
        },
        "_seq_no" : 15,
        "_primary_term" : 1,
        "status" : 201
      }
    },
    {
      "update" : {
        "_index" : "twitter",
        "_type" : "_doc",
        "_id" : "3",
        "_version" : 2,
        "result" : "updated",
        "_shards" : {
          "total" : 2,
          "successful" : 1,
          "failed" : 0
        },
        "_seq_no" : 16,
        "_primary_term" : 1,
        "status" : 200
      }
    },
    {
      "delete" : {
        "_index" : "twitter",
        "_type" : "_doc",
        "_id" : "6",
        "_version" : 2,
        "result" : "deleted",
        "_shards" : {
          "total" : 2,
          "successful" : 1,
          "failed" : 0
        },
        "_seq_no" : 17,
        "_primary_term" : 1,
        "status" : 200
      }
    }
  ]
}

我們再來批量查詢一下：

GET _mget
{
  "docs":[
    {
      "_index":"twitter",
      "_id":10
    },
    {
      "_index":"twitter",
      "_id":3
    },
    {
      "_index":"twitter",
      "_id":6
    }
  ]
}

返回結果：

{
  "docs" : [
    {
      "_index" : "twitter",
      "_type" : "_doc",
      "_id" : "10",
      "_version" : 1,
      "_seq_no" : 15,
      "_primary_term" : 1,
      "found" : true,
      "_source" : {
        "username" : "小飛飛",
        "age" : 12
      }
    },
    {
      "_index" : "twitter",
      "_type" : "_doc",
      "_id" : "3",
      "_version" : 2,
      "_seq_no" : 16,
      "_primary_term" : 1,
      "found" : true,
      "_source" : {
        "username" : "張三-update",
        "uid" : 3,
        "age" : 30
      }
    },
    {
      "_index" : "twitter",
      "_type" : "_doc",
      "_id" : "6",
      "found" : false
    }
  ]
}

發現數據都符合預期。

到這裏，發現了通過bulk創建文檔時，參數：{"index":{"_index":"twitter","_id":10}}裏的index其實是個動詞，即創建索引，特此說明。

x":“twitter”,
“_id”:10
},
{
“_index”:“twitter”,
“_id”:3
},
{
“_index”:“twitter”,
“_id”:6
}
]
}

返回結果：

```json
{
  "docs" : [
    {
      "_index" : "twitter",
      "_type" : "_doc",
      "_id" : "10",
      "_version" : 1,
      "_seq_no" : 15,
      "_primary_term" : 1,
      "found" : true,
      "_source" : {
        "username" : "小飛飛",
        "age" : 12
      }
    },
    {
      "_index" : "twitter",
      "_type" : "_doc",
      "_id" : "3",
      "_version" : 2,
      "_seq_no" : 16,
      "_primary_term" : 1,
      "found" : true,
      "_source" : {
        "username" : "張三-update",
        "uid" : 3,
        "age" : 30
      }
    },
    {
      "_index" : "twitter",
      "_type" : "_doc",
      "_id" : "6",
      "found" : false
    }
  ]
}

發現數據都符合預期。

到這裏，發現了通過bulk創建文檔時，參數：{"index":{"_index":"twitter","_id":10}}裏的index其實是個動詞，即創建索引，特此說明。