Elasticsearch的查询语言(DSL)真是不好写，偏偏查询的功能千奇百怪，filter/query/match/agg/geo各种各样，不管你是通过封装JSON还是通过python/java的api进行封装，都非常不方便。
最近发现了一个插件，Elasticsearch-SQL可以用sql查询Elasticsearch，感觉这个轮子造的真是好。
Elasticsearch-sql的项目地址：https://github.com/NLPchina/elasticsearch-sql
1、简介
Elasticsearch-sql实现的功能：
1)插件式的安装
2)SQL查询
3)超越SQL之外的查询
4)对JDBC方式的支持
2、插件式的安装
安装方法和elasticsearch-head的安装方法类似：
我们使用的es版本是2.1.1，如果你用的是不同的版本，可以在https://github.com/NLPchina/elasticsearch-sql找到支持。
$ cd ~/elasticsearch-2.1.1
$./bin/plugin install https://github.com/NLPchina/elasticsearch- sql/releases/download/2.1.1.1/elasticsearch-sql-2.1.1.1.zip
如果成功，命令行打印如下东东：
[bigdata-dw@bigdata-arch-client10 es2.1.1]$ ./bin/plugin install https://github.com/NLPchina/elasticsearch-sql/releases/download/2.1.1.1/elasticsearch-sql-2.1.1.1.zip
-> Installing from https://github.com/NLPchina/elasticsearch-sql/releases/download/2.1.1.1/elasticsearch-sql-2.1.1.1.zip...
Trying https://github.com/NLPchina/elasticsearch-sql/releases/download/2.1.1.1/elasticsearch-sql-2.1.1.1.zip ...
Downloading .................................................................................................................................................................................................................................................................................................................................................................................................................................................................DONE
Verifying https://github.com/NLPchina/elasticsearch-sql/releases/download/2.1.1.1/elasticsearch-sql-2.1.1.1.zip checksums if available ...
NOTE: Unable to verify checksum for downloaded plugin (unable to find .sha1 or .md5 file to verify)
Installed sql into /home/bigdata-dw/es2.1.1/plugins/sql
3、SQL查询
安装成功以后我们就可以通过sql查询ES了。
es-sql还提供了web页面，访问方式是http://10.93.18.34:9200/_plugin/sql/（如果你使用head，那么你的head访问应该是http://10.93.18.34:9200/_plugin/head/）
这里的ip和port是你安装es的主机和http端口。
访问到的页面是这样的
那么你现在有两种方式可以执行你的SQL：
1）在搜索框里直接输入你的sql了。（我的版本行尾不要写“；”否则会解析不了SQL）
2）通过http请求如
curl -XPOST http://10.93.18.34:8049/_sql -d 'SELECT * FROM audit where dDelay=-2053867461'
你会收到一个json格式的返回
{
"took": 2,
"timed_out": false,
"_shards": {
"total": 5,
"successful": 5,
"failed": 0
},
"hits": {
"total": 1,
"max_score": 12.549262,
"hits": [{
"_index": "audit",
"_type": "kafka",
"_id": "AVzzK-h_V9seINxbZ2Ox",
"_score": 12.549262,
"_source": {
"timestamp": "1498726500000",
"dCount": 680008,
"dDelay": -2053867461,
"cDelay": 0,
"clanName": "DJ_elk_common",
"checkTime": 1498728360063,
"cCount": 0,
"pCount": 680008,
"topicName": "DJ_elk_common_clean",
"pDelay": 370356423
}
}]
}
}
下面我们简单说4种类型的sql的书写方式：
1）query
SELECT * FROM bank WHERE age >30 AND gender = 'm'
2)aggregation
select COUNT(*),SUM(age),MIN(age) as m, MAX(age),AVG(age)
FROM bank GROUP BY gender ORDER BY SUM(age), m DESC
3)delete
DELETE FROM bank WHERE age >30 AND gender = 'm'
4)geo
SELECT * FROM locations WHERE GEO_BOUNDING_BOX(fieldname,100.0,1.0,101,0.0)
5)需要指定index type
SELECT * FROM indexName/type
6)如何指定路由
select /*! ROUTINGS(salary) */ sum(count) from index where type="salary"
4、对JDBC的支持
上述查询方式不管是直接在web上输入sql还是通过http请求。elasticsearch-sql还支持通过jdbc进行编程。
