Re: functions with side effect

On 07/19/2018 07:15 AM, Torsten Förtsch wrote:
> Hi,
> 
> assuming
> 
> SELECT nextval('s'), currval('s');
> 
> or
> 
> SELECT * FROM (VALUES (nextval('s'), currval('s'))) t;
> 
> is there any guarantee that the 2 output values are the same?

Assuming you are only working in single session:

https://www.postgresql.org/docs/10/static/functions-sequence.html

"currval

     Return the value most recently obtained by nextval for this 
sequence in the current session. (An error is reported if nextval has 
never been called for this sequence in this session.) Because this is 
returning a session-local value, it gives a predictable answer whether 
or not other sessions have executed nextval since the current session did."

> 
> Thanks,
> Torsten


-- 
Adrian Klaver
adrian.klaver@aklaver.com