文章目录
概述
继续跟中华石杉老师学习ES，第八篇
boost
https://www.elastic.co/guide/en/elasticsearch/reference/current/mapping-boost.html
知识点：
- 如果给某个字段设置boost 为2 ，则意味着改字段的权重比其他的值的权重大一倍 。权重值默认为1
- The boost is applied only for term queries (prefix, range and fuzzy queries are not boosted).
示例
数据如下：
{
"_index": "forum",
"_type": "article",
"_id": "5",
"_score": 1,
"_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"
}
},
{
"_index": "forum",
"_type": "article",
"_id": "2",
"_score": 1,
"_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"
}
},
{
"_index": "forum",
"_type": "article",
"_id": "4",
"_score": 1,
"_source": {
"articleID": "QQPX-R-3956-#aD8",
"userID": 2,
"hidden": true,
"postDate": "2017-01-02",
"tag": [
"java",
"elasticsearch"
],
"tag_cnt": 2,
"view_cnt": 80,
"title": "this is java, elasticsearch, hadoop blog"
}
},
{
"_index": "forum",
"_type": "article",
"_id": "1",
"_score": 1,
"_source": {
"articleID": "XHDK-A-1293-#fJ3",
"userID": 1,
"hidden": false,
"postDate": "2017-01-01",
"tag": [
"java",
"hadoop"
],
"tag_cnt": 2,
"view_cnt": 30,
"title": "this is java and elasticsearch blog"
}
},
{
"_index": "forum",
"_type": "article",
"_id": "3",
"_score": 1,
"_source": {
"articleID": "JODL-X-1937-#pV7",
"userID": 2,
"hidden": false,
"postDate": "2017-01-01",
"tag": [
"hadoop"
],
"tag_cnt": 1,
"view_cnt": 100,
"title": "this is elasticsearch blog"
}
}需求： 搜索标题中必须包含blog的帖子，同时如果标题中包含java或elasticsearch或hadoop或spark也要搜索出来，同时如果一个帖子包含spark，包含spark的帖子要优先其他帖子搜索出来
需求实现DSL如下：
GET /forum/article/_search
{
"query": {
"bool": {
"must": {
"match": {
"title": "blog"
}
},
"should": [
{
"match": {
"title": {
"query": "java"
}
}
},
{
"match": {
"title": {
"query": "elasticsearch"
}
}
},
{
"match": {
"title": {
"query": "hadoop"
}
}
},
{
"match": {
"title": {
"query": "spark",
"boost": 5
}
}
}
]
}
}
}
返回结果 ：
{
"took": 5,
"timed_out": false,
"_shards": {
"total": 5,
"successful": 5,
"skipped": 0,
"failed": 0
},
"hits": {
"total": 5,
"max_score": 1.7260925,
"hits": [
{
"_index": "forum",
"_type": "article",
"_id": "5",
"_score": 1.7260925,
"_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"
}
},
{
"_index": "forum",
"_type": "article",
"_id": "4",
"_score": 1.6185135,
"_source": {
"articleID": "QQPX-R-3956-#aD8",
"userID": 2,
"hidden": true,
"postDate": "2017-01-02",
"tag": [
"java",
"elasticsearch"
],
"tag_cnt": 2,
"view_cnt": 80,
"title": "this is java, elasticsearch, hadoop blog"
}
},
{
"_index": "forum",
"_type": "article",
"_id": "1",
"_score": 0.8630463,
"_source": {
"articleID": "XHDK-A-1293-#fJ3",
"userID": 1,
"hidden": false,
"postDate": "2017-01-01",
"tag": [
"java",
"hadoop"
],
"tag_cnt": 2,
"view_cnt": 30,
"title": "this is java and elasticsearch blog"
}
},
{
"_index": "forum",
"_type": "article",
"_id": "3",
"_score": 0.5753642,
"_source": {
"articleID": "JODL-X-1937-#pV7",
"userID": 2,
"hidden": false,
"postDate": "2017-01-01",
"tag": [
"hadoop"
],
"tag_cnt": 1,
"view_cnt": 100,
"title": "this is elasticsearch blog"
}
},
{
"_index": "forum",
"_type": "article",
"_id": "2",
"_score": 0.3971361,
"_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"
}
}
]
}
}可以看到spark的帖子，相关度得分最高，排在了第一位。
搜索条件的权重，boost，可以将某个搜索条件的权重加大，此时当匹配这个搜索条件和匹配另一个搜索条件的document，计算relevance score时，匹配权重更大的搜索条件的document，relevance score会更高，当然也就会优先被返回回来
我们如果把boost去掉会怎样呢？ 来看下
GET /forum/article/_search
{
"query": {
"bool": {
"must": {
"match": {
"title": "blog"
}
},
"should": [
{
"match": {
"title": {
"query": "java"
}
}
},
{
"match": {
"title": {
"query": "elasticsearch"
}
}
},
{
"match": {
"title": {
"query": "hadoop"
}
}
},
{
"match": {
"title": {
"query": "spark"
}
}
}
]
}
}
}
返回：
{
"took": 11,
"timed_out": false,
"_shards": {
"total": 5,
"successful": 5,
"skipped": 0,
"failed": 0
},
"hits": {
"total": 5,
"max_score": 1.6185135,
"hits": [
{
"_index": "forum",
"_type": "article",
"_id": "4",
"_score": 1.6185135,
"_source": {
"articleID": "QQPX-R-3956-#aD8",
"userID": 2,
"hidden": true,
"postDate": "2017-01-02",
"tag": [
"java",
"elasticsearch"
],
"tag_cnt": 2,
"view_cnt": 80,
"title": "this is java, elasticsearch, hadoop blog"
}
},
{
"_index": "forum",
"_type": "article",
"_id": "1",
"_score": 0.8630463,
"_source": {
"articleID": "XHDK-A-1293-#fJ3",
"userID": 1,
"hidden": false,
"postDate": "2017-01-01",
"tag": [
"java",
"hadoop"
],
"tag_cnt": 2,
"view_cnt": 30,
"title": "this is java and elasticsearch blog"
}
},
{
"_index": "forum",
"_type": "article",
"_id": "5",
"_score": 0.5753642,
"_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"
}
},
{
"_index": "forum",
"_type": "article",
"_id": "3",
"_score": 0.5753642,
"_source": {
"articleID": "JODL-X-1937-#pV7",
"userID": 2,
"hidden": false,
"postDate": "2017-01-01",
"tag": [
"hadoop"
],
"tag_cnt": 1,
"view_cnt": 100,
"title": "this is elasticsearch blog"
}
},
{
"_index": "forum",
"_type": "article",
"_id": "2",
"_score": 0.3971361,
"_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"
}
}
]
}
}spark的帖子并没有优先展示出来 ，可见boost权重确实起了作用。
