RE: [Proposal] Add foreign-server health checks infrastructure

Dear tom,

> I think that it's a really bad idea to require postgres_fdw.sql
> to have two expected-files: that will be a maintenance nightmare.
> Please put whatever it is that needs a variant expected-file
> into its own, hopefully very small and seldom-changed, test script.
> Or rethink whether you really need a test case that has
> platform-dependent output.

Thank you for giving the suggestion. I agreed your saying and modifed that.

I added new functions on the libpq and postgres-fdw layer that check whether the
checking works well or not. In the test, at first, the platform is checked and
the checking function is called only when it is supported.

An alternative approach is that PQCanConncheck() can be combined with PQConncheck().
This can reduce the libpq function, but we must define another returned value to
the function like -2. I was not sure which approach was better.

Best Regards,
Hayato Kuroda
FUJITSU LIMITED