ON COMMIT options for non temporary tables

On Thu, 2019-11-21 at 21:23 +0530, P V Tekawade wrote:

For my work with Postgres 11.5, I needed functionality that unlogged tables
are automatically dropped at the commit time, but I found that ON COMMIT
option is only supported with temporary table.
I would like to understand reasons why this option is limited to temporary tables?
Is there any problem by making this option available for other type of tables
such as unlogged tables?

How should that work for tables other than temporary tables?
Should COMMIT lock if somebody else accesses the table?

What keeps you from explicitly dropping the table right before
you commit?

Yours,
Laurenz Albe
--
Cybertec | https://www.cybertec-postgresql.com

On Thu, Nov 21, 2019 at 05:13:31PM +0100, Laurenz Albe wrote:

How should that work for tables other than temporary tables?
Should COMMIT lock if somebody else accesses the table?

Postgres does not support read uncommitted, so the table would not be
visible to other sessions until the transaction that created it is
committed. Anyway, the goal is to use the table just within a
transaction without having it produce WAL, right?

What keeps you from explicitly dropping the table right before
you commit?

Yeah, that would be the most simple. Another idea I can think of here
is to use a combination of event trigger and deferred triggered on a
dummy constraint: register the table creation using the event trigger
on CREATE TABLE, and then drop it using the deferred trigger. Using a
DROP TABLE before the commit or once your transaction is done with
this table is much more simple of course :)
--
Michael