Re: proposal: psql: psql variable BACKEND_PID
| От | Pavel Stehule |
|---|---|
| Тема | Re: proposal: psql: psql variable BACKEND_PID |
| Дата | |
| Msg-id | CAFj8pRD5ASGgKkH9wXiJF9ZEN5JAt+MAoUypt6byMvUW9gZFGw@mail.gmail.com обсуждение исходный текст |
| Ответ на | Re: proposal: psql: psql variable BACKEND_PID ("Daniel Verite" <daniel@manitou-mail.org>) |
| Список | pgsql-hackers |
po 6. 2. 2023 v 13:03 odesílatel Daniel Verite <daniel@manitou-mail.org> napsal:
I wrote:
> > In the varlistentry, I suggest we add "This variable is unset when the
> > connection is lost." after "but can be changed or unset.
>
> Personally I'd much rather have BACKEND_PID set to 0 rather than being unset
> when not connected. For one thing it allows safely using \if :BACKEND_PID.
Oops it turns out that was wishful thinking from me.
\if does not interpret a non-zero integer as true, except for the
value "1".
I'd still prefer BACKEND_PID being 0 when not connected, though.
I think psql never tries to execute a query if the engine is not connected, so for usage in queries undefined state is not important - it will be always defined.
for using in \if is unset may be a better state, because you can try to use {? varname} syntax.
0 is theoretically valid process id number, so I am not sure if 0 is ok. I don't know if some numbers can be used like invalid process id?
Best regards,
--
Daniel Vérité
https://postgresql.verite.pro/
Twitter: @DanielVerite
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