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elasticsearch-dynamic-synonym

An Elasticsearch token filter sopport load dynamic synonym.

Elasticsearch自带了一个synonym同义词插件,但是该插件只能使用文件或在分析器中静态地配置同义词,如果需要添加或修改,需要修改配置文件和重启,使用方式不够友好。通过学习Elasticsearch的synonym代码,自研了一个可动态维护同义词的插件,并以运用于生产环境。

Elasticsearch自带的SynonymTokenFilter

Elasticsearch自带的同义词过滤器支持在分析器配置(使用synonyms参数)和文件中配置(使用synonyms_path参数)同义词,配置方式如下:

{ "index" : { "analysis" : { "analyzer" : { "synonym_analyzer" : { "tokenizer" : "whitespace", "filter" : ["my_synonym"] } }, "filter" : { "my_synonym" : { "type" : "synonym", "expand": true, "ignore_case": true, "synonyms_path" : "analysis/synonym.txt" "synonyms" : ["阿迪, 阿迪达斯, adidasi => Adidas","Nike, 耐克, naike"] } } } } } 

在配置同义词规则时有Solr synonymsWordNet synonyms,一般我们使用的都是Solr synonyms。在配置时又存在映射和对等两种方式,区别如下:

// 精确映射同义词,【阿迪】、【阿迪达斯】和【adidasi】的token将会转换为【Adidas】存入倒排索引中 阿迪, 阿迪达斯, adidasi => Adidas // 对等同义词 // 当expand为true时,当出现以下任何一个token,三个token都会存入倒排索引中 // 当expand为false时,当出现以下任何一个token,第一个token也就是【Nike】会存入倒排索引中 Nike, 耐克, naike 

DynamicSynonymTokenFilter

实现方式

  • DynamicSynonymTokenFilter参考了SynonymTokenFilter的方式,但又予以简化,使用一个HashMap来保存同义词之间的转换关系;
  • DynamicSynonymTokenFilter只支持Solr synonyms,同时也支持expand和ignore_case参数的配置;
  • DynamicSynonymTokenFilter通过数据库来管理同义词的配置,并轮询数据库(通过version字段判断是否存在规则变化)实现同义词的动态管理;

安装

1.下载插件源码

git clone git@github.com:ginobefun/elasticsearch-dynamic-synonym.git 

2.使用maven编译插件

mvn clean install -DskipTests 

3.在ES_HOME/plugin目录新建dynamic-synonym目录,并将target/releases/elasticsearch-dynamic-synonym-<version>.zip文件解压到该目录

4.在MySQL中创建Elasticsearch同义词数据库并创建用户

create database elasticsearch; DROP TABLE IF EXISTS `dynamic_synonym_rule`; CREATE TABLE `dynamic_synonym_rule` ( `id` bigint(20) unsigned NOT NULL AUTO_INCREMENT, `rule` varchar(255) NOT NULL, `status` tinyint(1) NOT NULL DEFAULT '1' COMMENT '1: available, 0:unavailable', `version` int(11) NOT NULL, PRIMARY KEY (`id`), KEY `IDX_DYNAMIC_SYNONYM_VERSION` (`version`), KEY `IDX_DYNAMIC_SYNONYM_RULE` (`rule`) ) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=utf8; -- ---------------------------- -- insert sample records -- ---------------------------- INSERT INTO `dynamic_synonym_rule` VALUES ('1', '阿迪, 阿迪达斯, adidasi => Adidas', '1', '1'); INSERT INTO `dynamic_synonym_rule` VALUES ('2', 'Nike, 耐克, naike', '1', '2'); 

5.重启Elasticsearch

配置

Elasticsearch创建索引时配置分析器和过滤器:

PUT /index_synonym { "settings": { "analysis": { "analyzer": { "analyzer_with_dynamic_synonym": { "type": "custom", "tokenizer": "whitespace", "filter": ["my_synonym"] } }, "filter": { "my_synonym": { "type": "dynamic-synonym", "expand": true, "ignore_case": true, "tokenizer": "whitespace", "db_url": "jdbc:mysql://localhost:3306/elasticsearch?user=es_user&password=es_pwd&useUnicode=true&characterEncoding=UTF8" } } } } } 

设置Mapping

POST /index_synonym/product/_mapping { "product": { "properties": { "productName": { "type": "text", "analyzer": "analyzer_with_dynamic_synonym" } } } } 

使用

索引一些测试数据

POST /index_synonym/product/1 {"productName":"This is a nike shoes"} POST /index_synonym/product/2 {"productName":"This is a nike sports jacket"} POST /index_synonym/product/3 {"productName":"This is a adidas shoes"} POST /index_synonym/product/4 {"productName":"This is a adidas sports jacket"} POST /index_synonym/product/5 {"productName":"This is a vans shoes"} POST /index_synonym/product/6 {"productName":"This is a vans sports jacket"} 

测试分析器效果【耐克】

POST index_synonym/_search { "query": { "match": { "productName": "耐克" } } } { "took": 7, "timed_out": false, "_shards": { "total": 5, "successful": 5, "failed": 0 }, "hits": { "total": 2, "max_score": 2.4740286, "hits": [ { "_index": "index_synonym", "_type": "product", "_id": "2", "_score": 2.4740286, "_source": { "productName": "This is a nike sports jacket" } }, { "_index": "index_synonym", "_type": "product", "_id": "1", "_score": 0.85747814, "_source": { "productName": "This is a nike shoes" } } ] } } 

往数据库中插入一条同义词,测试【范斯】

INSERT INTO `dynamic_synonym_rule` VALUES ('3', 'Vans, 范斯', '1', '3'); // wait for 2 minutes to reload [2017-03-15 15:52:28,895][INFO ][node ] [node-local] started [2017-03-15 15:55:29,645][INFO ][dynamic-synonym ] Start to reload synonym rule... [2017-03-15 15:55:29,661][INFO ][dynamic-synonym ] Succeed to reload 3 synonym rule! POST index_synonym/_search { "query": { "match": { "productName": "范斯" } } } { "took": 4, "timed_out": false, "_shards": { "total": 5, "successful": 5, "failed": 0 }, "hits": { "total": 2, "max_score": 1.9490025, "hits": [ { "_index": "index_synonym", "_type": "product", "_id": "6", "_score": 1.9490025, "_source": { "productName": "This is a vans sports jacket" } }, { "_index": "index_synonym", "_type": "product", "_id": "5", "_score": 0.53484553, "_source": { "productName": "This is a vans shoes" } } ] } } 

总结与后续改进

  • 通过学习Elasticsearch源码自己实现了一个简易版的同义词插件,通过同义词的配置可以实现同义词规则的增删改的动态更新;
  • 需要注意的是,同义词的动态更新存在一个很重要的问题是原本在索引中已存在的数据不受同义词更新动态的影响,因此在使用时需要考虑是否可以容忍该问题,一个通常的做法是在某个时刻集中管理同义词,更新后执行索引重建动作;
  • 另外该插件目前存在一个问题,就是同义词的映射关系在内存中是一个全局数据,因此如果有多个不同的同义词过滤器则会存在问题,代码初始化时以第一个成功初始化的过滤器生成的映射关系为准,这个后续版本考虑改进。

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Elasticsearch Plugin for Dynaic Synonym Token Filter.

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