Implementation of global temporary tables?

* We have unlogged tables

Opened questions:

1. Name and conformance with standard of this feature - because we doesn't support modules, a mapping ANSI -> PG should not be trivial

2. Implementation

I see three possible ways how to implement it:

2.a - using on demand created temp tables - most simple solution, but doesn't help with catalogue bloating

2.b - using unlogged tables for holding statistics, relfilenode, and all necessary data

3.c - store ephemeral metadata only in memory without MVCC

Is there still interest about this feature?

Comments, notes?

Pavel