概述
继续跟中华石杉老师学习ES，第26篇
课程地址： https://www.roncoo.com/view/55
官方说明
https://www.elastic.co/guide/en/elasticsearch/reference/current/query-dsl-function-score-query.html
简单来说： 自定义一个function_score函数，自己将某个field的值，跟es内置算出来的分数进行运算，然后由自己指定的field来进行分数的增强
例子
需求： 看帖子的人越多，那么帖子的分数就越高
先给所有的帖子数据增加follower数量 ， 将对帖子搜索得到的分数，跟follower_num进行运算，由follower_num在一定程度上增强帖子的分数
看帖子的人越多，那么帖子的分数就越高
POST /forum/article/_bulk { "update": { "_id": "1"} } { "doc" : {"follower_num" : 5} } { "update": { "_id": "2"} } { "doc" : {"follower_num" : 10} } { "update": { "_id": "3"} } { "doc" : {"follower_num" : 25} } { "update": { "_id": "4"} } { "doc" : {"follower_num" : 3} } { "update": { "_id": "5"} } { "doc" : {"follower_num" : 60} }
DSL
GET /forum/article/_search { "query": { "function_score": { "query": { "multi_match": { "query": "java spark", "fields": ["tile", "content"] } }, "field_value_factor": { "field": "follower_num", "modifier": "log1p", "factor": 0.5 }, "boost_mode": "sum", "max_boost": 5 } } }
如果只有field，那么会将每个doc的分数都乘以follower_num，如果有的doc follower是0，那么分数就会变为0，效果很不好。
因此一般会加个log1p函数，公式会变为，new_score = old_score * log(1 + number_of_votes)，这样出来的分数会比较合理 。
- 再加个factor，可以进一步影响分数，
new_score = old_score * log(1 + factor * number_of_votes)
- boost_mode，可以决定分数与指定字段的值如何计算 : multiply，replace, sum，min，max，avg
max_boost，限制计算出来的分数不要超过max_boost指定的值
返回结果：
{ "took": 87, "timed_out": false, "_shards": { "total": 1, "successful": 1, "skipped": 0, "failed": 0 }, "hits": { "total": 2, "max_score": 3.8050528, "hits": [ { "_index": "forum", "_type": "article", "_id": "5", "_score": 3.8050528, "_source": { "articleID": "DHJK-B-1395-#Ky5", "userID": 3, "hidden": false, "postDate": "2019-05-01", "tag": [ "elasticsearch" ], "tag_cnt": 1, "view_cnt": 10, "title": "this is spark blog", "content": "spark is best big data solution based on scala ,an programming language similar to java spark", "sub_title": "haha, hello world", "author_first_name": "Tonny", "author_last_name": "Peter Smith", "new_author_last_name": "Peter Smith", "new_author_first_name": "Tonny", "follower_num": 60 } }, { "_index": "forum", "_type": "article", "_id": "2", "_score": 1.7247463, "_source": { "articleID": "KDKE-B-9947-#kL5", "userID": 1, "hidden": false, "postDate": "2017-01-02", "tag": [ "java" ], "tag_cnt": 1, "view_cnt": 50, "title": "this is java blog", "content": "i think java is the best programming language", "sub_title": "learned a lot of course", "author_first_name": "Smith", "author_last_name": "Williams", "new_author_last_name": "Williams", "new_author_first_name": "Smith", "follower_num": 10 } } ] } }
