Elasticsearch 6.3 X-PACK SQL Overview，

Elasticsearch 6.3 X-PACK SQL Overview

Elasticsearch SQL aims to provide a powerful yet lightweight SQL interface to Elasticsearch

写在前面

However the backing engine itself is Elasticsearch for which Elasticsearch SQL was purposely created hence why features or concepts that are not available, or cannot be mapped correctly, in SQL appear in Elasticsearch SQL. Last but not least, Elasticsearch SQL tries to obey the principle of least suprise, though as all things in the world, everything is relative.

Elasticsearch终究是Elasticsearch，不能够完全兼容SQL。开发者们尽量准守principle of least suprise(最小惊吓原则)来开发Elasticsearch SQL。

Overview

X-PACK SQL支持以REST API、SQL CLI客户端以及JDBC的形式连接Elasticsearch。

Mapping concepts across SQL and Elasticsearch

SQL	Elasticsearch
column	field
row	document
table	index
schema	implicit
database	cluster

SQL REST API

支持txt,json,yaml,smile,cbor,csv

SQL Translate API

将SQL语句转换为Elasticsearch查询语法

POST /_xpack/sql/translate
{
    "query": "SELECT * FROM library ORDER BY page_count DESC",
    "fetch_size": 10
}

SQL CLI

$ ./bin/elasticsearch-sql-cli https://some.server:9200

SQL JDBC

这部分未进一步探索，因为这个功能是收费的

<dependency>
  <groupId>org.elasticsearch.plugin</groupId>
  <artifactId>jdbc</artifactId>
  <version>6.3.2</version>
</dependency>

存在的问题

Reference

SQL Access