PG federated tables listing

[rafatower]

This implements listing of remote schemas and tables, from a federated server, registered or not.

A few important remarks:

• It does not depend on any extra extension (e.g dblink nor patches in postgres_fdw)
• It imports a couple foreign views into the local schema given by __CDB_User_FDW_Object_Names(). The target schema may be changed to avoid conflicts.
• Potentially they may return more info, such as the the table_type. I stuck to the essence until we clear out some doubts
• IMO there should be functions to list registered tables and to list ALL foreign tables (registered or not). API-wise this may be solved by adding a column registered bool IF we have a solid convention to place federated objects and at the expense of complexity.

@Algunenano at this point I'm more concerned about the interface and the relations between the functions than in the implementation. What do you think?

Thanks!

[Algunenano]

It does not depend on any extra extension (e.g dblink nor patches in postgres_fdw) This is great.

@Algunenano at this point I'm more concerned about the interface and the relations between the functions than in the implementation. What do you think?

Agreed. This is going to break against the conventions I'm using for the other functions. Do you mind if I take these functions and incorporate them into my branch / PR in a consistent way?

IMO there should be functions to list registered tables and to list ALL foreign tables (registered or not). API-wise this may be solved by adding a column registered bool IF we have a solid convention to place federated objects and at the expense of complexity.

I'm going to keep them separated for now, we can join them before merge / release.

[rafatower]

Do you mind if I take these functions and incorporate them into my branch / PR in a consistent way?

Not at all! On the contrary, I really appreciate it :heart: Glad we're not stepping too much on each other's toes too.

[rafatower]

Closing in favor of Raul's branch