# match_phrase_prefix 实现搜索推荐
# 什么是搜索推荐（search-time）？
比如搜索 hello world，但是你在输入到 hello w 的时候，就会出现以下的一些数据
hello world
hello we
hello win
hello wind
hello dog
hello cat
hello w -->
hello world
hello we
hello win
hello wind
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例如百度中搜索 --> elas --> elasticsearch --> elasticsearch权威指南
# match_phrase_prefix
GET /forum/article/_search
{
"query": {
"match_phrase_prefix": {
"content": "java i"
}
}
}
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响应结果
{
"took": 106,
"timed_out": false,
"_shards": {
"total": 5,
"successful": 5,
"failed": 0
},
"hits": {
"total": 2,
"max_score": 1.1648302,
"hits": [
{
"_index": "forum",
"_type": "article",
"_id": "2",
"_score": 1.1648302,
"_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": "6",
"_score": 0.8480819,
"_source": {
"content": "java is my favourite programming language, and I also think spark is a very good big data system."
}
}
]
}
}
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原理跟 match_phrase 类似，唯一的区别，就是把最后一个 term 作为前缀去搜索：
java i分词- 使用 java match
- 最后一个 term 「i」会作为前缀去扫描整个倒排索引，找到所有已 i 开头的 doc
- 然后找到既满足第 2 条，又满足第 3 条的 doc
复杂的语法如下
GET /forum/article/_search
{
"query": {
"match_phrase_prefix": {
"content": {
"query": "java i",
"slop":10,
"max_expansions": 2
}
}
}
}
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slop：只有最有一个 term 会作为前缀
max_expansions：指定 prefix 最多匹配多少个 term，超过这个数量就不继续匹配了，限定性能
具体是什么规则我也没有搞懂，和 slop 一起使用才能限制。测试中没有看出来什么规则
尽量不要用，因为，最后一个前缀始终要去扫描大量的索引，性能可能会很差