| From: | Fabien COELHO <coelho(at)cri(dot)ensmp(dot)fr> | 
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> | 
| Cc: | Corey Huinker <corey(dot)huinker(at)gmail(dot)com>, PostgreSQL Developers <pgsql-hackers(at)postgresql(dot)org> | 
| Subject: | Re: Undefined psql variables | 
| Date: | 2017-04-02 20:33:06 | 
| Message-ID: | alpine.DEB.2.20.1704022221390.9265@lancre | 
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| Thread: | |
| Lists: | pgsql-hackers | 
Hello,
>> For checking variable definition, I would suggest to extend the variable
>> access syntax so that there is no exception to the one thing rule between
>> client side and server side evaluation:
>
>>    \if :?variable
>
> Don't like that one bit;
Possibly:-)
This is kind of a shell-like hack ${VAR:?error-message-if-not-defined},
or ${#VAR} to get a length.
They are not likable but they do the job.
> you're going to run out of namespace there in no time.
I do not undestand where there would be a namespace issue. Is that under 
the assumption that ":?xxx" is frequently used in SQL?
> And you don't have a very good way to say "if not defined", either.
Indeed. I'm afraid that handling "NOT" client-side would be necessary with 
this approach, so the decision would be 1 thing or 2 things where the 
first one is "NOT" would be handled client-side.
-- 
Fabien.
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