Support Information Functions for MySQL

[tristaZero]

Which version of ShardingSphere did you use?

4.0.0.0-RC1

Which project did you use? Sharding-JDBC or Sharding-Proxy?

Sharding-Proxy

Expected behavior

1. input select database();
2. return current schema name;

Actual behavior

1. input select database();
2. return actual data node name, e.g.

mysql> select database();
+-----------------+
| database()      |
+-----------------+
| demo_ds_slave_0 |
+-----------------+

Reason analyze (If you can)

Steps to reproduce the behavior, such as: SQL to execute, sharding rule configuration, when exception occur etc.

Example codes for reproduce this issue (such as a github link).

[Moriadry-zz]

Hi miss, I am wondering do you guys get a way to integration test sharding-proxy, I don't know how to debug this kind of bugs locally.

[tuohai666]

@moriadry
Download sharding-proxy from: https://www.apache.org/dyn/closer.cgi?path=incubator/shardingsphere/4.0.0-RC1/apache-shardingsphere-incubating-4.0.0-RC1-sharding-proxy-bin.tar.gz
You can start this binary package locally. Don't forget to copy mysql-connector-java-5.1.47 to lib directory manually.

[Moriadry-zz]

Get it.

[terrymanu]

FYI: https://dev.mysql.com/doc/refman/8.0/en/information-functions.html

[totalo]

Hello, I want to try to do this. I want to know whether we aggregate the data of these Informations or choose a table to display. How do we distinguish nodes from different sources when we aggregate?

[sandynz]

In 5.0.0-RC1, test result:

mysql> select database();
+-------------+
| DATABASE()  |
+-------------+
| sharding_db |
+-------------+

It's already implemented in #8539, related code is ShowCurrentDatabaseExecutor:

    public void execute(final BackendConnection backendConnection) {
        mergedResult = new SingleLocalDataMergedResult(Collections.singleton(backendConnection.getSchemaName()));
    }

It return current connection related schema name.