Elasticsearch - SQL訪問

這是一個元件，允許對 Elasticsearch 執行類似 SQL 的即時查詢。您可以將 Elasticsearch SQL 視為一個翻譯器，它同時理解 SQL 和 Elasticsearch，並利用 Elasticsearch 的功能，輕鬆地即時、大規模地讀取和處理資料。

Elasticsearch SQL 的優勢

• 原生整合 − 每個查詢都根據底層儲存有效地針對相關節點執行。

• 無需外部元件 − 無需額外的硬體、程序、執行時或庫來查詢 Elasticsearch。

• 輕量級且高效 − 它採用並公開 SQL，允許進行適當的全文搜尋，即時進行。

示例

PUT /schoollist/_bulk?refresh
   {"index":{"_id": "CBSE"}}
   {"name": "GleanDale", "Address": "JR. Court Lane", "start_date": "2011-06-02",
   "student_count": 561}
   {"index":{"_id": "ICSE"}}
   {"name": "Top-Notch", "Address": "Gachibowli Main Road", "start_date": "1989-
   05-26", "student_count": 482}
   {"index":{"_id": "State Board"}}
   {"name": "Sunshine", "Address": "Main Street", "start_date": "1965-06-01",
   "student_count": 604}

執行上述程式碼後，我們將獲得如下所示的響應：

{
   "took" : 277,
   "errors" : false,
   "items" : [
      {
         "index" : {
            "_index" : "schoollist",
            "_type" : "_doc",
            "_id" : "CBSE",
            "_version" : 1,
            "result" : "created",
            "forced_refresh" : true,
            "_shards" : {
               "total" : 2,
               "successful" : 1,
               "failed" : 0
            },
            "_seq_no" : 0,
            "_primary_term" : 1,
            "status" : 201
         }
      },
      {
         "index" : {
            "_index" : "schoollist",
            "_type" : "_doc",
            "_id" : "ICSE",
            "_version" : 1,
            "result" : "created",
            "forced_refresh" : true,
            "_shards" : {
               "total" : 2,
               "successful" : 1,
               "failed" : 0
            },
            "_seq_no" : 1,
            "_primary_term" : 1,
            "status" : 201
         }
      },
      {
         "index" : {
            "_index" : "schoollist",
            "_type" : "_doc",
            "_id" : "State Board",
            "_version" : 1,
            "result" : "created",
            "forced_refresh" : true,
            "_shards" : {
               "total" : 2,
               "successful" : 1,
               "failed" : 0
            },
            "_seq_no" : 2,
            "_primary_term" : 1,
            "status" : 201
         }
      }
   ]
}

SQL 查詢

以下示例顯示瞭如何構建 SQL 查詢：

POST /_sql?format=txt
{
   "query": "SELECT * FROM schoollist WHERE start_date < '2000-01-01'"
}

執行上述程式碼後，我們將獲得如下所示的響應：

Address             | name          | start_date             | student_count
--------------------+---------------+------------------------+---------------
Gachibowli Main Road|Top-Notch      |1989-05-26T00:00:00.000Z|482
Main Street         |Sunshine       |1965-06-01T00:00:00.000Z|604

注意 − 透過更改上面的 SQL 查詢，您可以獲得不同的結果集。