ElasticSearch7.3学习(三十)----ES7.X SQL新特性解析及使用Java api实现sql功能

一、ES7 sql新特性

1.1 数据准备

创建索引及映射

建立价格、颜色、品牌、售卖日期 四个字段

PUT /tvs

PUT /tvs/_mapping
{
  "properties": {
    "price": {
      "type": "long"
    },
    "color": {
      "type": "keyword"
    },
    "brand": {
      "type": "keyword"
    },
    "sold_date": {
      "type": "date"
    }
  }
}

插入数据

POST /tvs/_bulk
{"index":{}}
{"price":1000,"color":"红色","brand":"长虹","sold_date":"2019-10-28"}
{"index":{}}
{"price":2000,"color":"红色","brand":"长虹","sold_date":"2019-11-05"}
{"index":{}}
{"price":3000,"color":"绿色","brand":"小米","sold_date":"2019-05-18"}
{"index":{}}
{"price":1500,"color":"蓝色","brand":"TCL","sold_date":"2019-07-02"}
{"index":{}}
{"price":1200,"color":"绿色","brand":"TCL","sold_date":"2019-08-19"}
{"index":{}}
{"price":2000,"color":"红色","brand":"长虹","sold_date":"2019-11-05"}
{"index":{}}
{"price":8000,"color":"红色","brand":"三星","sold_date":"2020-01-01"}
{"index":{}}
{"price":2500,"color":"蓝色","brand":"小米","sold_date":"2020-02-12"}

1.2 简单示例

POST /_sql?format=txt
{
  "query": "SELECT * FROM tvs "
}

返回类似于数据库的界面

二、启动方式

2.1 http请求

POST /_sql?format=txt
{
  "query": "SELECT * FROM tvs "
}

2.2 客户端启动

elasticsearch-sql-cli.bat

双击执行，在控制台输入show tables;即可查询到ES中所有的索引

2.3 Java代码

这种方式在下面会介绍

三、显示方式

上面的ES语句中可以看到format = txt，这个是控制返回结果为txt格式，当然也支持其他的格式。如下图所示

可以简单的看下其他的格式，例如说tsv,以tab做分割的格式

例如说csv

四、sql 翻译

既然支持sql语句，那么底层是怎么运行的呢？ 实际上还是转换成query语句来执行，我们可以用translate来查看一下

五、与其他DSL结合

也可以与其他查询语句相结合使用，例如说，查询价格在1200~2000范围内的数据

六、Java 代码实现sql功能

6.1 免费试用sql功能

如果要使用代码实现sql功能，对于ES来说就要收费了。必须具备白金版功能，没有的话 Java代码会报错current license is non-compliant for [jdbc]

java.sql.SQLInvalidAuthorizationSpecException: current license is non-compliant for [jdbc]
	at org.elasticsearch.xpack.sql.client.JreHttpUrlConnection$SqlExceptionType.asException(JreHttpUrlConnection.java:321)
	at org.elasticsearch.xpack.sql.client.JreHttpUrlConnection.parserError(JreHttpUrlConnection.java:198)
	at org.elasticsearch.xpack.sql.client.JreHttpUrlConnection.request(JreHttpUrlConnection.java:161)
	at org.elasticsearch.xpack.sql.client.HttpClient.lambda$post$1(HttpClient.java:105)
	at org.elasticsearch.xpack.sql.client.JreHttpUrlConnection.http(JreHttpUrlConnection.java:65)
	at org.elasticsearch.xpack.sql.client.HttpClient.lambda$post$2(HttpClient.java:104)
	at java.security.AccessController.doPrivileged(Native Method)
	at org.elasticsearch.xpack.sql.client.HttpClient.post(HttpClient.java:103)
	at org.elasticsearch.xpack.sql.client.HttpClient.query(HttpClient.java:80)
	at org.elasticsearch.xpack.sql.jdbc.JdbcHttpClient.query(JdbcHttpClient.java:68)
	at org.elasticsearch.xpack.sql.jdbc.JdbcStatement.initResultSet(JdbcStatement.java:160)
	at org.elasticsearch.xpack.sql.jdbc.JdbcStatement.execute(JdbcStatement.java:151)
	at org.elasticsearch.xpack.sql.jdbc.JdbcStatement.executeQuery(JdbcStatement.java:40)
	at com.itheima.es.TestJdbc.main(TestJdbc.java:17)

当然我们可以免费试用一段时间

kibana中管理 ==> 许可管理  ==> 开启白金版试用

6.2 导入依赖

    <dependency>
        <groupId>org.elasticsearch.plugin</groupId>
        <artifactId>x-pack-sql-jdbc</artifactId>
        <version>7.3.0</version>
    </dependency>
    
    <repositories>
        <repository>
            <id>elastic.co</id>
            <url>https://artifacts.elastic.co/maven</url>
        </repository>
    </repositories>

6.3 Java代码

    public static void main(String[] args) {
        //1创建连接
        try {
            Connection connection = DriverManager.getConnection("jdbc:es://http://localhost:9200");
            //2创建statement
            Statement statement = connection.createStatement();
            //3执行sql语句
            ResultSet resultSet = statement.executeQuery("select * from tvs");
            //4获取结果
            while (resultSet.next()) {
                String str = resultSet.getString(1)+","
                        +resultSet.getString(2)+","
                        +resultSet.getString(3)+","
                        +resultSet.getString(4);
                System.out.println(str);
                System.out.println("======================================");
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

返回结果