Question

我的Oracle数据库中有这个SQL查询和EVENT表。

SELECT *
FROM (SELECT
CITY,
max(DATE) AS eventdate
FROM EVENT
WHERE TYPE = 'CRASH'
GROUP BY CITY
ORDER BY eventdate DESC, CITY ASC)
WHERE ROWNUM < 6;

NEW YORK 15/02/27
LONDON 15/02/27
LONDON 15/02/27
LONDON 15/02/11
LONDON 15/02/19

EVENT: ID, NAME, DATE, CITY, TYPE

我想使用JavaAPI在ElasticSearch中执行相同的查询。可能吗？我是初学者，不知道如何开始。 documentation没有任何我的案例，或者我看不到它们。

我必须知道有最新活动和日期的6个城市。然后我会向ElasticSearch询问这些城市的3个最后事件。我想我必须做两个查询，因为在一个响应中不可能有这样的结果：CITY-＆gt; listOf3LastEvents，CITY2-＆gt; listOf3LastEvents，City3-＆gt; listOf3LastEvents

Answer 1

好的，让我们说你的活动文件只是这样建模：

{
   "id": 123,
   "name": "Some event name",
   "event_date": "2016-09-02T12:00:00.000Z",
   "city": "New York",
   "type": "CRASH"
}

现在让我们创建一个索引，其中包含上述文档的合理映射：

PUT events
{
  "mappings": {
    "event": {
      "properties": {
        "id": {
          "type": "long"
        },
        "type": {
          "type": "string",
          "index": "not_analyzed"
        },
        "event_date": {
          "type": "date"
        },
        "city": {
          "type": "string",
          "fields": {
            "raw": {
              "type": "string",
              "index": "not_analyzed"
            }
          }
        },
        "name": {
          "type": "string"
        }
      }
    }
  }
}

我们现在可以使用以下命令索引上述文档（+其他几个）：

PUT events/event/123
{
   "id": 123,
   "name": "Some event name",
   "event_date": "2016-09-02T12:00:00.000Z",
   "city": "New York",
   "type": "CRASH"
}

最后，您将能够发送一个与您的SQL查询等效的查询：

POST events/event/_search
{
  "size": 0,
  "query": {
    "term": {
      "type": "CRASH"
    }
  },
  "aggs": {
    "cities": {
      "terms": {
        "field": "city.raw",
        "size": 6,
        "order": {
          "latest": "desc"
        }
      },
      "aggs": {
        "latest": {
          "max": {
            "field": "event_date"
          }
        },
        "last_3_events": {
          "top_hits": {
            "size": 3,
            "sort": {
              "event_date": "desc"
            }
          }
        }
      }
    }
  }
}

坚持ElasticSearch GroupBy查询

1 个答案: