1、什么是召回率？
比如你搜索一个java spark，总共有100个doc，能返回多少个doc作为结果，就是召回率，recall
2、什么是精准度？
比如你搜索一个java spark，能不能尽可能让包含java spark或者是java和spark离的很近的doc排在最前面，precision直接用match_phrase短语搜索，会导致必须所有term都在doc field中出现，而且距离在slop限定范围内才能匹配上。
match_phrase,proximity match要求doc必须包含所有的term，才能作为结果返回；如果某一个doc可能就是有某个term没有包含，那么就无法作为结果返回。
比如：
java spark --》 hello world java ： 就无法匹配到
java spark --》 hello world，java spark ： 可以匹配到
3、疑问
近似匹配的时候，召回率比较低，精准度太高了，但是有时我们希望的是匹配到几个term中的部分，就可以作为结果出来，这样可以提高召回率，同时我们也希望用上match_phrase根据距离提升分数的功能，让几个term距离越近分数就越高，越优先返回。
就是优先满足召回率。比如
java spark --》 包含java的返回，包含spark的也返回，包含 java和spark的也返回，同时兼顾精准度，就是包含java和spark，同时java和spark距离越近的doc排最前面。
4、解决疑问
可以用bool组合match query和match_phrase query一起，来实现上述效果。
match提高召回率，带java和带spark的都要返回。
match_phrase提高精准度，保证同时带java和spark的排在最前面。
效果1：直接用bool match query
GET /forum/article/_search
{
"query": {
"bool": {
"must": [
{
"match": {
"content": "java spark"
}
}
]
}
}
}
结果
{
"took": 54,
"timed_out": false,
"_shards": {
"total": 5,
"successful": 5,
"failed": 0
},
"hits": {
"total": 2,
"max_score": 0.68640786,
"hits": [
{
"_index": "forum",
"_type": "article",
"_id": "2",
"_score": 0.68640786,
"_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"
}
},
{
"_index": "forum",
"_type": "article",
"_id": "5",
"_score": 0.68324494,
"_source": {
"articleID": "DHJK-B-1395-#Ky5",
"userID": 3,
"hidden": false,
"postDate": "2017-03-01",
"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"
}
}
]
}
}
结果发现单独包含java和spark的也被返回了，而且单独包含java的却排到了第一位，既包含java又包含spark的却排到了最后。
效果2：直接用match_phrase
GET /forum/article/_search
{
"query": {
"match_phrase": {
"content": {
"query": "java spark",
"slop" : 50
}
}
}
}
结果：
{
"took": 3,
"timed_out": false,
"_shards": {
"total": 5,
"successful": 5,
"failed": 0
},
"hits": {
"total": 1,
"max_score": 0.5753642,
"hits": [
{
"_index": "forum",
"_type": "article",
"_id": "5",
"_score": 0.5753642,
"_source": {
"articleID": "DHJK-B-1395-#Ky5",
"userID": 3,
"hidden": false,
"postDate": "2017-03-01",
"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"
}
}
]
}
}
结果发现只返回了既包含java又包含spark的数据，召回率降低了。
最终效果：我们将两个结果合并，既用bool match query又用match_phrase
GET /forum/article/_search
{
"query": {
"bool": {
"must": [
{
"match": {
"content": "java spark"
}
}
],
"should": [
{
"match_phrase": {
"content": {
"query": "java spark",
"slop" : 50
}
}
}
]
}
}
}
结果:
{
"took": 4,
"timed_out": false,
"_shards": {
"total": 5,
"successful": 5,
"failed": 0
},
"hits": {
"total": 2,
"max_score": 1.258609,
"hits": [
{
"_index": "forum",
"_type": "article",
"_id": "5",
"_score": 1.258609,
"_source": {
"articleID": "DHJK-B-1395-#Ky5",
"userID": 3,
"hidden": false,
"postDate": "2017-03-01",
"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"
}
},
{
"_index": "forum",
"_type": "article",
"_id": "2",
"_score": 0.68640786,
"_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"
}
}
]
}
}
结果发现非常完美，两个都包含的排到了第一位，并且分数远高于第二个。而且召回率也很高
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