如何從彈性搜索中獲取max _id

Question

我創建了一條河，每小時運行一條河從DB中獲取數據（使用jdbc河插件）。

select * from orders 

而是選擇我要選擇是基於初級key.Query附加將數據全部記錄：

select * from orders where deviceid > '(Max Id in Elastic search)' 

？我怎樣才能從彈性最大搜索_id？

Answer 1

由於ES堅持將"_id"的值轉換爲字符串，似乎沒有辦法直接使用"_id"字段。但是有一種解決方法。

首先，我建立了一個簡單的指標有幾個文檔，如下所示：

PUT /test_index 
{ 
    "settings": { 
     "number_of_shards": 1 
    } 
} 

POST /test_index/_bulk 
{"index":{"_index":"test_index","_type":"doc","_id":1}} 
{"title":"first doc"} 
{"index":{"_index":"test_index","_type":"doc","_id":2}} 
{"title":"second doc"} 
{"index":{"_index":"test_index","_type":"doc","_id":3}} 
{"title":"third doc"} 

然後我試圖使用max aggregation，卻得到了一個錯誤，因爲"_id" s爲字符串：

POST /test_index/_search?search_type=count 
{ 
    "aggs": { 
     "max_id": { 
     "max": { 
      "field": "_id" 
     } 
     } 
    } 
} 
... 
{ 
    "error": "SearchPhaseExecutionException[Failed to execute phase [query], all shards failed; shardFailures {[bQS7TqO9SfKSPQZYVXQBag][test_index][0]: ClassCastException[org.elasticsearch.index.fielddata.plain.PagedBytesIndexFieldData cannot be cast to org.elasticsearch.index.fielddata.IndexNumericFieldData]}]", 
    "status": 500 
} 

所以這是行不通的。但是，使用"_id" field中的"path"參數稍作修改。

所以我重新定義索引

DELETE /test_index 

PUT /test_index 
{ 
    "settings": { 
     "number_of_shards": 1 
    }, 
    "mappings": { 
     "doc": { 
     "_id": { 
      "path": "doc_id" 
     } 
     } 
    } 
} 

，然後索引使用"doc_id"路徑文檔：

POST /test_index/_bulk 
{"index":{"_index":"test_index","_type":"doc"}} 
{"title":"first doc","doc_id":1} 
{"index":{"_index":"test_index","_type":"doc"}} 
{"title":"second doc","doc_id":2} 
{"index":{"_index":"test_index","_type":"doc"}} 
{"title":"third doc","doc_id":3} 

現在，如果我搜索，我可以看到"_id"仍然是一個字符串，但"doc_id"是一個整數：

POST /test_index/_search 
... 
{ 
    "took": 1, 
    "timed_out": false, 
    "_shards": { 
     "total": 1, 
     "successful": 1, 
     "failed": 0 
    }, 
    "hits": { 
     "total": 3, 
     "max_score": 1, 
     "hits": [ 
     { 
      "_index": "test_index", 
      "_type": "doc", 
      "_id": "1", 
      "_score": 1, 
      "_source": { 
       "title": "first doc", 
       "doc_id": 1 
      } 
     }, 
     { 
      "_index": "test_index", 
      "_type": "doc", 
      "_id": "2", 
      "_score": 1, 
      "_source": { 
       "title": "second doc", 
       "doc_id": 2 
      } 
     }, 
     { 
      "_index": "test_index", 
      "_type": "doc", 
      "_id": "3", 
      "_score": 1, 
      "_source": { 
       "title": "third doc", 
       "doc_id": 3 
      } 
     } 
     ] 
    } 
} 

所以現在我可以方便地使用最大聚集找到值的最大ID：

POST /test_index/_search?search_type=count 
{ 
    "aggs": { 
     "max_id": { 
     "max": { 
      "field": "doc_id" 
     } 
     } 
    } 
} 
... 
{ 
    "took": 1, 
    "timed_out": false, 
    "_shards": { 
     "total": 1, 
     "successful": 1, 
     "failed": 0 
    }, 
    "hits": { 
     "total": 3, 
     "max_score": 0, 
     "hits": [] 
    }, 
    "aggregations": { 
     "max_id": { 
     "value": 3 
     } 
    } 
}