ElasticSearch7.3学习(二十七)----聚合概念（bucket和metric）及其示例

一、两个核心概念：bucket和metric

1.1 bucket

有如下数据

city	name
北京	张三
北京	李四
天津	王五
天津	赵六
天津	王麻子

划分出来两个bucket，一个是北京bucket，一个是天津bucket

北京bucket：包含了2个人，张三，李四

上海bucket：包含了3个人，王五，赵六，王麻子

1.2 metric

metric，就是对一个bucket执行的某种聚合分析的操作，比如说求平均值，求最大值，求最小值

比如下面的一个sql语句

select count(*) from book group studymodel

bucket：group by studymodel --> 那些studymodel相同的数据，就会被划分到一个bucket中

metric：count(*)，对每个bucket中所有的数据，计算一个数量。例如avg()，sum()，max()，min()

二、聚合示例

2.1 数据准备

首先创建book索引

PUT /book/
{"settings": {"number_of_shards": 1,"number_of_replicas": 0},"mappings": {"properties": {"name": {"type": "text","analyzer": "ik_max_word","search_analyzer": "ik_smart"},"description": {"type": "text","analyzer": "ik_max_word","search_analyzer": "ik_smart"},"studymodel": {"type": "keyword"},"price": {"type": "double"},"timestamp": {"type": "date","format": "yyyy-MM-dd HH:mm:ss||yyyy-MM-dd||epoch_millis"},"pic": {"type": "text","index": false}}}
}

添加测试数据

PUT /book/_doc/1
{"name": "Bootstrap开发","description": "Bootstrap是一个非常流行的开发框架。此开发框架可以帮助不擅长css页面开发的程序人员轻松的实现一个css，不受浏览器限制的精美界面css效果。","studymodel": "201002","price": 38.6,"timestamp": "2019-08-25 19:11:35","pic": "group1/M00/00/00/wKhlQFs6RCeAY0pHAAJx5ZjNDEM428.jpg","tags": ["bootstrap","dev"]
}PUT /book/_doc/2
{"name": "java编程思想","description": "java语言是世界第一编程语言，在软件开发领域使用人数最多。","studymodel": "201001","price": 68.6,"timestamp": "2019-08-25 19:11:35","pic": "group1/M00/00/00/wKhlQFs6RCeAY0pHAAJx5ZjNDEM428.jpg","tags": ["java","dev"]
}PUT /book/_doc/3
{"name": "spring开发基础","description": "spring 在java领域非常流行，java程序员都在用。","studymodel": "201001","price": 88.6,"timestamp": "2019-08-24 19:11:35","pic": "group1/M00/00/00/wKhlQFs6RCeAY0pHAAJx5ZjNDEM428.jpg","tags": ["spring","java"]
}

2.2 计算每个studymodel下的商品数量

sql语句： select studymodel，count(*) from book group by studymodel

"size": 0, ==> 作用：只需要聚合的数据，不需要查询的数据

GET /book/_search
{"size": 0,"query": {"match_all": {}},"aggs": {"group_by_model": {"terms": {"field": "studymodel"}}}
}

结果：

{"took" : 2,"timed_out" : false,"_shards" : {"total" : 1,"successful" : 1,"skipped" : 0,"failed" : 0},"hits" : {"total" : {"value" : 3,"relation" : "eq"},"max_score" : null,"hits" : [ ]},"aggregations" : {"group_by_model" : {"doc_count_error_upper_bound" : 0,"sum_other_doc_count" : 0,"buckets" : [{"key" : "201001","doc_count" : 2},{"key" : "201002","doc_count" : 1}]}}
}

2.3 计算每个tags下的商品数量

设置字段"fielddata": true，不设置会报错

PUT /book/_mapping/
{"properties": {"tags": {"type": "text","fielddata": true}}
}

查询

GET /book/_search
{"size": 0, "query": {"match_all": {}}, "aggs": {"group_by_tags": {"terms": { "field": "tags" }}}
}

结果：

{"took" : 2,"timed_out" : false,"_shards" : {"total" : 1,"successful" : 1,"skipped" : 0,"failed" : 0},"hits" : {"total" : {"value" : 3,"relation" : "eq"},"max_score" : null,"hits" : [ ]},"aggregations" : {"group_by_tags" : {"doc_count_error_upper_bound" : 0,"sum_other_doc_count" : 0,"buckets" : [{"key" : "dev","doc_count" : 2},{"key" : "java","doc_count" : 2},{"key" : "bootstrap","doc_count" : 1},{"key" : "spring","doc_count" : 1}]}}
}

2.4 加上搜索条件，计算每个tags下的商品数量

GET /book/_search
{"size": 0, "query": {"match": {"description": "java程序员"}}, "aggs": {"group_by_tags": {"terms": { "field": "tags" }}}
}

结果：

{"took" : 70,"timed_out" : false,"_shards" : {"total" : 1,"successful" : 1,"skipped" : 0,"failed" : 0},"hits" : {"total" : {"value" : 2,"relation" : "eq"},"max_score" : null,"hits" : [ ]},"aggregations" : {"group_by_tags" : {"doc_count_error_upper_bound" : 0,"sum_other_doc_count" : 0,"buckets" : [{"key" : "java","doc_count" : 2},{"key" : "dev","doc_count" : 1},{"key" : "spring","doc_count" : 1}]}}
}

2.5 计算每个tag下的商品的平均价格

子聚合

GET /book/_search
{"size": 0,"aggs": {"group_by_tags": {"terms": {"field": "tags"},"aggs": {"avg_price": {"avg": {"field": "price"}}}}}
}

结果：

{"took" : 0,"timed_out" : false,"_shards" : {"total" : 1,"successful" : 1,"skipped" : 0,"failed" : 0},"hits" : {"total" : {"value" : 3,"relation" : "eq"},"max_score" : null,"hits" : [ ]},"aggregations" : {"group_by_tags" : {"doc_count_error_upper_bound" : 0,"sum_other_doc_count" : 0,"buckets" : [{"key" : "dev","doc_count" : 2,"avg_price" : {"value" : 53.599999999999994}},{"key" : "java","doc_count" : 2,"avg_price" : {"value" : 78.6}},{"key" : "bootstrap","doc_count" : 1,"avg_price" : {"value" : 38.6}},{"key" : "spring","doc_count" : 1,"avg_price" : {"value" : 88.6}}]}}
}

2.6 计算每个tag下的商品的平均价格，按照平均价格降序排序

小技巧，如果是查询全部，match_all可省略

GET /book/_search
{"size": 0,"aggs": {"group_by_tags": {"terms": {"field": "tags","order": {"avg_price": "desc"}},"aggs": {"avg_price": {"avg": {"field": "price"}}}}}
}

结果：

{"took" : 4,"timed_out" : false,"_shards" : {"total" : 1,"successful" : 1,"skipped" : 0,"failed" : 0},"hits" : {"total" : {"value" : 3,"relation" : "eq"},"max_score" : null,"hits" : [ ]},"aggregations" : {"group_by_tags" : {"doc_count_error_upper_bound" : 0,"sum_other_doc_count" : 0,"buckets" : [{"key" : "spring","doc_count" : 1,"avg_price" : {"value" : 88.6}},{"key" : "java","doc_count" : 2,"avg_price" : {"value" : 78.6}},{"key" : "dev","doc_count" : 2,"avg_price" : {"value" : 53.599999999999994}},{"key" : "bootstrap","doc_count" : 1,"avg_price" : {"value" : 38.6}}]}}
}

2.7 按照指定的价格范围区间进行分组，然后在每组内再按照tag进行分组，最后再计算每组的平均价格

GET /book/_search
{"size": 0,"aggs": {"group_by_price": {"range": {"field": "price","ranges": [{"from": 0,"to": 40},{"from": 40,"to": 60},{"from": 60,"to": 80}]},"aggs": {"group_by_tags": {"terms": {"field": "tags"},"aggs": {"average_price": {"avg": {"field": "price"}}}}}}}
}

结果：

{"took" : 5,"timed_out" : false,"_shards" : {"total" : 1,"successful" : 1,"skipped" : 0,"failed" : 0},"hits" : {"total" : {"value" : 3,"relation" : "eq"},"max_score" : null,"hits" : [ ]},"aggregations" : {"group_by_price" : {"buckets" : [{"key" : "0.0-40.0","from" : 0.0,"to" : 40.0,"doc_count" : 1,"group_by_tags" : {"doc_count_error_upper_bound" : 0,"sum_other_doc_count" : 0,"buckets" : [{"key" : "bootstrap","doc_count" : 1,"average_price" : {"value" : 38.6}},{"key" : "dev","doc_count" : 1,"average_price" : {"value" : 38.6}}]}},{"key" : "40.0-60.0","from" : 40.0,"to" : 60.0,"doc_count" : 0,"group_by_tags" : {"doc_count_error_upper_bound" : 0,"sum_other_doc_count" : 0,"buckets" : [ ]}},{"key" : "60.0-80.0","from" : 60.0,"to" : 80.0,"doc_count" : 1,"group_by_tags" : {"doc_count_error_upper_bound" : 0,"sum_other_doc_count" : 0,"buckets" : [{"key" : "dev","doc_count" : 1,"average_price" : {"value" : 68.6}},{"key" : "java","doc_count" : 1,"average_price" : {"value" : 68.6}}]}}]}}
}

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