Support DistSQL with ShardingSphere-JDBC for upgrade easier

[terrymanu]

DistSQLis supported by ShardingSphere-Proxy only, it maybe not enough.
I just open to discuss the benefit of support DistSQL with ShardingSphere-JDBC too.

For the 3.x or 4.x version of Apache ShardingSphere, there are lots of configuration types, such as: Java Code, YAML, Spring namespace and Spring boot starter.
The configuration of 5.x version's is not compatible with previous versions, it is not easy to upgrade.
The good way to help old friends upgrade to new version quickly is using DistSQL.

We can provide the config-DistSQL conversion tool to generate DistSQL to configure the 5.x version. It is easy to save it as init.sql and execute before ShardingSphere startup.

In future, it may possible to instead of Java Config and YAML with DistSQL, and simplify spring namespace and spring boot starter to care about data source only.

What do you think?

Link to #13287

[RaigorJiang]

This is a good idea. Converting the configuration to DistSQL can indeed help users reduce the trouble caused by changes in the configuration file format.
In fact, we have previously discussed providing a conversion tool to Proxy users to help them convert from configuration files to the use of DistSQL, and your proposal allows us to expand our imagination, thank you!

Speaking back of ShardingSphere-JDBC, many users are still accustomed to using yaml or properties configuration files. We can allow DistSQL to be used together with configuration files. For example, first load the data sources or some rules from the configuration file, and then dynamically configure additional rules through DistSQL.

[terrymanu]

Yes, I agree.
DistSQL is optional of ShardingSphere-JDBC, user can use prefer configuration way as they want.
It is the way for upgrade to new version for now.

Maybe in future, DistSQL is well known by most of users, then we can consider about simplify other configuration types.