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
代码语言：javascript复制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
代码语言：javascript复制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：
代码语言：javascript复制{
"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
}
}
]
}
}
