There is a problem with the compatibility for Confluence 5.9.1.
SAL was upgraded to 3.0.5,
The Postgres driver only works in the JDBC 4.1 version, and it can't use JDBC 4.2.
I didn't notice it while testing, because it was installed through the SDK. It needs to be fixed.
Since it is not easy to debug the bug above, we're introducing a diagnostics screen. To reach it:
You must be an administrator
Set the system property -Dplaysql.diagnostics. This system property doesn't impact the performance and can remain active.
Go to the Play SQL administration and click "Diagnostics".
Be aware that it actually changes data if you make edit rows/execute SQL.