ES聚合之Pipeline聚合语法讲解
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目录
目标
掌握Pipeline aggregations（管道聚合，相当于mysql中的having ）的基本语法。它比另外两种类型的聚合用得较少，这里只举了少量案例供大家参考分析。Pipeline aggregations分为两类：
- Parent（父级）：结果内嵌到现有的聚合结果中。
- Sibling（兄弟级）：结果和现有的聚合结果同级。
ES版本信息
7.17.5
官方文档
Pipeline aggregations
https://www.elastic.co/guide/en/elasticsearch/reference/7.17/search-aggregations-pipeline.html
实战
新增测试数据
#图书馆数据库
PUT /library_db
"settings":
"index":
"analysis.analyzer.default.type": "ik_max_word"
PUT /library_db/_bulk
"index":"_id":"1"
"id":1,"type":"玄幻","name":"诛仙","words_num":120,"chapter_num":600,"completion_time":"2000-09-01","author":"萧鼎","prices":32.12
"index":"_id":"2"
"id":2,"type":"玄幻","name":"诛仙前传：蛮荒行","words_num":30,"chapter_num":67,"completion_time":"2020-09-01","author":"萧鼎","prices":23.12
"index":"_id":"3"
"id":3,"type":"武侠","name":"天龙八部","words_num":80,"chapter_num":120,"completion_time":"1995-09-01","author":"金庸","prices":52.1
"index":"_id":"4"
"id":4,"type":"武侠","name":"射雕英雄传","words_num":67,"chapter_num":95,"completion_time":"1998-01-01","author":"金庸","prices":4.12
"index":"_id":"5"
"id":5,"type":"武侠","name":"神雕侠侣","words_num":75,"chapter_num":76,"completion_time":"2000-01-01","author":"金庸","prices":32.8
"index":"_id":"6"
"id":5,"type":"武侠","name":"倚天屠龙记","words_num":83,"chapter_num":130,"completion_time":"2003-01-01","author":"金庸","prices":100.12
"index":"_id":"7"
"id":7,"type":"玄幻","name":"凡人修仙传","words_num":600,"chapter_num":3000,"completion_time":"2018-01-01","author":"忘语","prices":120.12
"index":"_id":"8"
"id":8,"type":"玄幻","name":"魔天记","words_num":159,"chapter_num":400,"completion_time":"2019-01-01","author":"忘语","prices":11.12
"index":"_id":"9"
"id":9,"type":"都市异能","name":"黄金瞳","words_num":220,"chapter_num":400,"completion_time":"2019-01-01","author":"打眼","prices":74.5
"index":"_id":"10"
"id":10,"type":"玄幻","name":"将夜","words_num":210,"chapter_num":600,"completion_time":"2014-01-01","author":"血红","prices":32.0
"index":"_id":"11"
"id":11,"type":"军事","name":"亮剑","words_num":120,"chapter_num":100,"completion_time":"2012-01-01","author":"都梁","prices":15.0基本语法
需求一：求每个作者下面字数最多的小说的字数，按照作品数量降序排序。
分析：第一步求出每个作者的小说数量，按照降序排序；第二步求出每个作者下字数最多的小说的字数。
POST /library_db/_search
"size": 0,
"aggs":
"author_group":
"terms":
"field": "author.keyword",
"size": 10,
"order":
"_key": "desc"
,
"aggs":
"max_words_num":
"max":
"field": "words_num"
需求二：求小说的每个类型的平均字数，求出最大的平均字数。
POST /library_db/_search
"size": 0,
"aggs":
"author_group":
"terms":
"field": "type.keyword",
"size": 10,
"order":
"_key": "desc"
,
"aggs":
"avg_words_num":
"avg":
"field": "words_num"
,
"max_avg_words_num":
"max_bucket":
"buckets_path": "author_group>avg_words_num"
百分数分桶聚合
需求：求小说的每个类型的平均字数，求出平均字数的百分位。
POST /library_db/_search
"size": 0,
"aggs":
"author_group":
"terms":
"field": "type.keyword",
"size": 10,
"order":
"_key": "desc"
,
"aggs":
"avg_words_num":
"avg":
"field": "words_num"
,
"percentiles_avg_words_num":
"percentiles_bucket":
"buckets_path": "author_group>avg_words_num",
"percents": [ 25.0, 50.0, 75.0,100 ]
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