• Elasticserch学习之聚合


    Elasticsearch有一个功能叫做聚合(aggregations),它允许你在数据上生成复杂的分析统计。它很像SQL中的GROUP BY但是功能更强大。

    示例:找到所有职员中最大的共同点(兴趣爱好)。

    GET /megacorp/employee/_search
    {
      "aggs": {
        "all_interests": {
          "terms": { "field": "interests" }
        }
      }
    }

    暂时先忽略语法只看查询结果:

    {
       ...
       "hits": { ... },
       "aggregations": {
          "all_interests": {
             "buckets": [
                {
                   "key":       "music",
                   "doc_count": 2
                },
                {
                   "key":       "forestry",
                   "doc_count": 1
                },
                {
                   "key":       "sports",
                   "doc_count": 1
                }
             ]
          }
       }
    }

    示例:所有姓"Smith"的人最大的共同点(兴趣爱好)。

    GET /megacorp/employee/_search
    {
      "query": {
        "match": {
          "last_name": "smith"
        }
      },
      "aggs": {
        "all_interests": {
          "terms": {
            "field": "interests"
          }
        }
      }
    }

    all_interests聚合已经变成只包含和查询语句相匹配的文档了:

    ...
      "all_interests": {
         "buckets": [
            {
               "key": "music",
               "doc_count": 2
            },
            {
               "key": "sports",
               "doc_count": 1
            }
         ]
      }

    示例:统计每种兴趣下职员的平均年龄。

    GET /megacorp/employee/_search
    {
        "aggs" : {
            "all_interests" : {
                "terms" : { "field" : "interests" },
                "aggs" : {
                    "avg_age" : {
                        "avg" : { "field" : "age" }
                    }
                }
            }
        }
    }

    结果:

      ...
      "all_interests": {
         "buckets": [
            {
               "key": "music",
               "doc_count": 2,
               "avg_age": {
                  "value": 28.5
               }
            },
            {
               "key": "forestry",
               "doc_count": 1,
               "avg_age": {
                  "value": 35
               }
            },
            {
               "key": "sports",
               "doc_count": 1,
               "avg_age": {
                  "value": 25
               }
            }
         ]
      }
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  • 原文地址:https://www.cnblogs.com/mentiantian/p/10510658.html
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