Re: [HACKERS] proposal: schema variables

On Wed, Sep 19, 2018 at 02:08:04PM +0200, Pavel Stehule wrote:
> Unfortunately we cannot to use standard
> "SET" command, because it is used in Postgres for different purpose.
> READ|WRITE are totally clear, and for user it is another signal so
> variables are different than tables (so it is not one row table).
> 
> I prefer current state, but if common opinion will be different, I have not
> problem to change it.

I see. I grepped the thread before writhing this but somehow missed the
discussion.

> The content of variables is not transactional (by default). It is not
> destroyed by rollback. So I have to calculate with rollback too. So the
> most correct syntax should be "ON COMMIT ON ROLLBACK RESET" what is little
> bit messy and I used "ON TRANSACTION END". It should be signal, so this
> event is effective on rollback event and it is valid for not transaction
> variable. This logic is not valid to transactional variables, where ON
> COMMIT RESET has sense. But this behave is not default and then I prefer
> more generic syntax.
> ...
> So I see two different cases - work with catalog (what is transactional)
> and work with variable value, what is (like other variables in programming
> languages) not transactional. "ON TRANSACTION END RESET" means - does reset
> on any transaction end.
> 
> I hope so I explained it cleanly - if not, please, ask.

I understood what you mean, thank you. I thought that
{ ON COMMIT DROP | ON TRANSACTION END RESET } parameters are used only
for transactional variables in the first place. But is there any sense
in using this parameters with non-transactional variables? That is when
we create non-transactional variable we don't want that the variable
will rollback or reset its value after the end of a transaction.

-- 
Arthur Zakirov
Postgres Professional: http://www.postgrespro.com
Russian Postgres Company