ShardingSphere-Proxy v5.4.1 how to use DB Gateway？

[liuaiolos]

In DB Gateway document. It says:

Currently, only MySQL/PostgreSQL dialects can be automatically translated. Engineers can use MySQL dialects and protocols to access PostgreSQL databases and vice versa.

But I don't konw how to use the feature. I want to use Mysql client to access PostgreSQL database.
I try to set server.yaml's props:proxy-frontend-database-protocol-type: MySQL
And config-yaml dataSources to jdbc:postgresql.
I can use MySQL cli client to connect to ShardingSphere-Proxy and see the database.
But show tables command return nothing. I can't see any tables.
Here's my yaml files.
yaml.zip
By the way: If I change the server.yaml's proxy-frontend-database-protocol-type to PostgreSQL and use psql client to connect. It works well.