Implementation of global temporary tables?

Hello

Six years ago we did discuss about global temporary tables - persistent
schema, ephemeral data.

http://postgresql.nabble.com/idea-global-temp-tables-td2007217.html

I am thinking so some reasons why implement this feature are valid:

* we can get some performance benefit against current temp tables - less
the catalogue bloating,

* we can simplify a static validation of plpgsql functions when temp tables
are used,
more global temp tables are little bit comfortable for developers,

* we can simplify migration from some other databases, where global temp
tables are default.

Some was changed from 2009:

* We have updatable CTE

* 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