ElasticSearch SQL 访问

SQL 访问

它是允许对 Elasticsearch 实时执行类似SQL的查询的组件。您可以将Elasticsearch SQL视为一种翻译器，它既可以理解SQL又可以使用Elasticsearch，并且可以利用Elasticsearch功能轻松地进行大规模实时读取和处理数据。

Elasticsearch SQL的优点

它具有本机集成-根据基础存储，对相关节点高效地执行每个查询。
无需外部零件-无需额外的硬件，流程，运行时或库即可查询Elasticsearch。
轻巧高效-它包含并公开了SQL，可以实时进行适当的全文本搜索。

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}

运行上面的代码后，我们得到如下所示的响应：


{
   "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查询

以下示例显示了如何构建SQL查询-


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

运行上面的代码后，我们得到如下所示的响应：


      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-通过更改上面的SQL查询，您可以获得不同的结果集。