分词深入剖析"/>
Elasticsearch Index查询优化及Mapping分词深入剖析
本套技术专栏作者(秦凯新)专注于大数据及容器云核心技术解密,具备5年工业级IOT大数据云平台建设经验,可提供全栈的大数据+云原生平台咨询方案,请持续关注本套博客。QQ邮箱地址:1120746959@qq,如有任何学术交流,可随时联系。
1 multi-index和multi-type搜索模式
/_search:所有索引,所有type下的所有数据都搜索出来/index1/_search:指定一个index,搜索其下所有type的数据/index1,index2/_search:同时搜索两个index下的数据/*1,*2/_search:按照通配符去匹配多个索引/index1/type1/_search:搜索一个index下指定的type的数据/index1/type1,type2/_search:可以搜索一个index下多个type的数据/index1,index2/type1,type2/_search:搜索多个index下的多个type的数据/_all/type1,type2/_search:_all,可以代表搜索所有index下的指定type的数据
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2 分页搜索(防止Deep Paging)
- size 表示页大小,from表示从第几个document开始查询
GET /_search?size=10GET /_search?size=10&from=0GET /_search?size=10&from=20GET /test_index/test_type/_search"hits": {"total": 9,"max_score": 1,
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- 我们假设将这9条数据分成3页,每一页是3条数据,来实验一下这个分页搜索的效果
GET /test_index/test_type/_search?from=0&size=3{"took": 2,"timed_out": false,"_shards": {"total": 5,"successful": 5,"failed": 0},"hits": {"total": 9,"max_score": 1,"hits": [{"_index": "test_index","_type": "test_type","_id": "8","_score": 1,"_source": {"test_field": "test client 2"}},{"_index": "test_index","_type": "test_type","_id": "6","_score": 1,"_source": {"test_field": "tes test"}},{"_index": "test_index","_type": "test_type","_id": "4","_score": 1,"_source": {"test_field": "test4"}}]}}第一页:id=8,6,4GET /test_index/test_type/_search?from=3&size=3第二页:id=2,自动生成,7GET /test_index/test_type/_search?from=6&size=3第三页:id=1,11,3
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3 mapping原理
3.1 dynamic mapping初体验
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自动或手动为index中的type建立的一种数据结构和相关配置,简称为mapping。
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dynamic mapping,自动为我们建立index,创建type,以及type对应的mapping,mapping中包含了每个field对应的数据类型,以及如何分词等设置 我们当然,后面会讲解,也可以手动在创建数据之前,先创建index和type,以及type对应的mapping。
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插入几条数据,让es自动为我们建立一个索引
PUT /website/article/1{"post_date": "2017-01-01","title": "my first article","content": "this is my first article in this website","author_id": 11400}PUT /website/article/2{"post_date": "2017-01-02","title": "my second article","content": "this is my second article in this website","author_id": 11400}PUT /website/article/3{"post_date": "2017-01-03","title": "my third article","content": "this is my third article in this website","author_id": 11400}
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- 尝试各种搜索(发现不能做到精确匹配)
GET /website/article/_search?q=2017 3条结果 GET /website/article/_search?q=2017-01-01 3条结果GET /website/article/_search?q=post_date:2017-01-01 1条结果GET /website/article/_search?q=post_date:2017 1条结果
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- 查看mapping,搜索结果为什么不一致,因为es自动建立mapping的时候,设置了不同的field不同的data type。不同的data type的分词、搜索等行为是不一样的。所以出现了_all field和post_date field的搜索表现完全不一样。
GET /website/_mapping/article{"website": {"mappings": {"article": {"properties": {"author_id": {"type": "long"},"content": {"type": "text","fields": {"keyword": {"type": "keyword","ignore_above": 256}}},"post_date": {"type": "date"},"title": {"type": "text","fields": {"keyword": {"type": "keyword","ignore_above": 256}}}}}}}}
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3.2 dynamic mapping揭秘
- 分词,初步的倒排索引的建立
doc1:I really liked my small dogs, and I think my mom also liked them.
doc2:He never liked any dogs, so I hope that my mom will not expect me to liked him.复制代码
- 执行搜索
mother like little dog,不可能有任何结果。这个是不是我们想要的搜索结果???绝对不是,因为在我们看来,mother和mom有区别吗?同义词,都是妈妈的意思。like和liked有区别吗?没有,都是喜欢的意思,只不过一个是现在时,一个是过去时。little和small有区别吗?同义词,都是小小的。dog和dogs有区别吗?狗,只不过一个是单数,一个是复数。
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- normalization,建立倒排索引的时候,会执行一个操作,也就是说对拆分出的各个单词进行相应的处理,以提升后面搜索的时候能够搜索到相关联的文档的概率
时态的转换,单复数的转换,同义词的转换,大小写的转换mom —> motherliked —> likesmall —> littledogs —> dog
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重新建立倒排索引,加入normalization,再次用mother liked little dog搜索,就可以搜索到了
3.3 什么是分词器
- 切分词语,normalization(提升recall召回率),例如:给你一段句子,然后将这段句子拆分成一个一个的单个的单词,同时对每个单词进行normalization(时态转换,单复数转换),分瓷器 recall,召回率:搜索的时候,增加能够搜索到的结果的数量
character filter:在一段文本进行分词之前,先进行预处理,比如说最常见的就是,过滤html标签(<span>hello<span> --> hello),& --> and(I&you --> I and you)tokenizer:分词,hello you and me --> hello, you, and, metoken filter:lowercase,stop word,synonymom,dogs --> dog,liked --> like,Tom --> tom,a/the/an --> 干掉,mother --> mom,small --> little
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一个分词器,很重要,将一段文本进行各种处理,最后处理好的结果才会拿去建立倒排索引
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内置分词器的介绍
Set the shape to semi-transparent by calling set_trans(5)standard analyzer:set, the, shape, to, semi, transparent, by, calling, set_trans, 5(默认的是standard)simple analyzer:set, the, shape, to, semi, transparent, by, calling, set, transwhitespace analyzer:Set, the, shape, to, semi-transparent, by, calling, set_trans(5)language analyzer(特定的语言的分词器,比如说,english,英语分词器):set, shape, semi, transpar, call, set_tran, 5
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3.4 遗留问题揭秘
- query string分词
query string必须以和index建立时相同的analyzer进行分词query string对exact value和full text的区别对待知识点:不同类型的field,可能有的就是full text,有的就是exact valuepost_date,date:exact value_all:full text,分词,normalizationGET /_search?q=2017搜索的是_all field,document所有的field都会拼接成一个大串,进行分词2017-01-02 my second article this is my second article in this website 11400doc1 doc2 doc32017 * * *01 * 02 *03 *_all,2017,自然会搜索到3个docuemntGET /_search?q=2017-01-01_all,2017-01-01,query string会用跟建立倒排索引一样的分词器去进行分词20170101GET /_search?q=post_date:2017-01-01date,会作为exact value去建立索引doc1 doc2 doc32017-01-01 * 2017-01-02 * 2017-01-03 *post_date:2017-01-01,2017-01-01,doc1一条documentGET /_search?q=post_date:2017,这个在这里不讲解,因为是es 5.2以后做的一个优化复制代码
- 测试分词器
GET /_analyze{"analyzer": "standard","text": "Text to analyze"}
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3.5 Mapping原理
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往es里面直接插入数据,es会自动建立索引,同时建立type以及对应的mapping
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mapping中就自动定义了每个field的数据类型
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不同的数据类型(比如说text和date),可能有的是exact value,有的是full text
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exact value,在建立倒排索引的时候,分词的时候,是将整个值一起作为一个关键词建立到倒排索引中的;full text,会经历各种各样的处理,分词,normaliztion(时态转换,同义词转换,大小写转换),才会建立到倒排索引中
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同时呢,exact value和full text类型的field就决定了,在一个搜索过来的时候,对exact value field或者是full text field进行搜索的行为也是不一样的,会跟建立倒排索引的行为保持一致;比如说exact value搜索的时候,就是直接按照整个值进行匹配,full text query string,也会进行分词和normalization再去倒排索引中去搜索
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可以用es的dynamic mapping,让其自动建立mapping,包括自动设置数据类型;也可以提前手动创建index和type的mapping,自己对各个field进行设置,包括数据类型,包括索引行为,包括分词器,等等
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mapping,就是index的type的元数据,每个type都有一个自己的mapping,决定了数据类型,建立倒排索引的行为,还有进行搜索的行为
3.6 Mapping数据结构
- 核心的数据类型
stringbyte,short,integer,longfloat,doublebooleandate
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- dynamic mapping
true or false --> boolean123 --> long123.45 --> double2017-01-01 --> date"hello world" --> string/text
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- 查看mapping
GET /index/_mapping/type
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3.7 Mapping手动建立索引
- 如何建立索引
analyzednot_analyzedno
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- 修改mapping
PUT /website{"mappings": {"article": {"properties": {"author_id": {"type": "long"},"title": {"type": "text","analyzer": "english"},"content": {"type": "text"},"post_date": {"type": "date"},"publisher_id": {"type": "text","index": "not_analyzed"}}}}}
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- 如下修改索引,是会报错的
PUT /website{"mappings": {"article": {"properties": {"author_id": {"type": "text"}}}}}{"error": {"root_cause": [{"type": "index_already_exists_exception","reason": "index [website/co1dgJ-uTYGBEEOOL8GsQQ] already exists","index_uuid": "co1dgJ-uTYGBEEOOL8GsQQ","index": "website"}],"type": "index_already_exists_exception","reason": "index [website/co1dgJ-uTYGBEEOOL8GsQQ] already exists","index_uuid": "co1dgJ-uTYGBEEOOL8GsQQ","index": "website"},"status": 400}
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- 修改索引正确方法
PUT /website/_mapping/article{"properties" : {"new_field" : {"type" : "string","index": "not_analyzed"}}}
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- 测试mapping
GET /website/_analyze{"field": "content","text": "my-dogs" }GET website/_analyze{"field": "new_field","text": "my dogs"}{"error": {"root_cause": [{"type": "remote_transport_exception","reason": "[4onsTYV][127.0.0.1:9300][indices:admin/analyze[s]]"}],"type": "illegal_argument_exception","reason": "Can't process field [new_field], Analysis requests are only supported on tokenized fields"},"status": 400}
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- multivalue field,建立索引时与string是一样的,数据类型不能混
{ "tags": [ "tag1", "tag2" ]}
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- empty field
null,[],[null]
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- object field
PUT /company/employee/1{"address": {"country": "china","province": "guangdong","city": "guangzhou"},"name": "jack","age": 27,"join_date": "2017-01-01"}address:object类型GET /company/_mapping/employee{"company": {"mappings": {"employee": {"properties": {"address": {"properties": {"city": {"type": "text","fields": {"keyword": {"type": "keyword","ignore_above": 256}}},"country": {"type": "text","fields": {"keyword": {"type": "keyword","ignore_above": 256}}},"province": {"type": "text","fields": {"keyword": {"type": "keyword","ignore_above": 256}}}}},"age": {"type": "long"},"join_date": {"type": "date"},"name": {"type": "text","fields": {"keyword": {"type": "keyword","ignore_above": 256}}}}}}}}复制代码
- ES底层数据结构1
{"address": {"country": "china","province": "guangdong","city": "guangzhou"},"name": "jack","age": 27,"join_date": "2017-01-01"}{"name": [jack],"age": [27],"join_date": [2017-01-01],"address.country": [china],"address.province": [guangdong],"address.city": [guangzhou]}
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- ES底层数据结构2
{"authors": [{ "age": 26, "name": "Jack White"},{ "age": 55, "name": "Tom Jones"},{ "age": 39, "name": "Kitty Smith"}]}{"authors.age": [26, 55, 39],"authors.name": [jack, white, tom, jones, kitty, smith]}
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4 Query DSL 分析
- Query DSL使用
GET /_search{"query": {"match_all": {}}}
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- Query DSL的基本语法
{QUERY_NAME: {ARGUMENT: VALUE,ARGUMENT: VALUE,...}}{QUERY_NAME: {FIELD_NAME: {ARGUMENT: VALUE,ARGUMENT: VALUE,...}}}GET /test_index/test_type/_search {"query": {"match": {"test_field": "test"}}}
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- 如何组合多个搜索条件,搜索需求:title必须包含elasticsearch,content可以包含elasticsearch也可以不包含,author_id必须不为111
GET /website/article/_search{"query": {"bool": {"must": [{"match": {"title": "elasticsearch"}}],"should": [{"match": {"content": "elasticsearch"}}],"must_not": [{"match": {"author_id": 111}}]}}}GET /test_index/_search{"query": {"bool": {"must": { "match": { "name": "tom" }},"should": [{ "match": { "hired": true }},{ "bool": {"must": { "match": { "personality": "good" }},"must_not": { "match": { "rude": true }}}}],"minimum_should_match": 1}}
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5 总结
生产部署还有很多工作要做,本文从初级思路切入,进行了问题的整合。
本套技术专栏作者(秦凯新)专注于大数据及容器云核心技术解密,具备5年工业级IOT大数据云平台建设经验,可提供全栈的大数据+云原生平台咨询方案,请持续关注本套博客。QQ邮箱地址:1120746959@qq,如有任何学术交流,可随时联系。
秦凯新
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