Re: Desirability of client-side expressions in psql?

2018-06-24 16:13 GMT+02:00 Fabien COELHO <coelho(at)cri(dot)ensmp(dot)fr>:

>
> Hello Pavel,
>
> This is a discussion without actual patch intended for pg12, to be added
>>>> to CF 2018-09. The expected end result is either "returned with
>>>> feedback",
>>>> meaning proceed to send some big patch(es), or "rejected", meaning the
>>>> project does not want this, no point in submitting something.
>>>>
>>>
>> please, can you port expression evaluation from pgbench to psql? I miss a
>> patch.
>>
>
> Indeed, I have not done it yet:-)
>
> This is a pretty large series of patches, which would take a significant
> time for developing (me), rewiewing (not me) and committing (with overload
> committers). I would not like to end in the "we do not want this feature at
> all" state *after* the time has been spent, hence this pre-patch call for
> discussion about the feature itself, before diving into coding.
>
> I take note that you are interested in actually having this feature.
>
> I am sure so psql expression evaluation has strong benefit - mainly for
>> expressions like
>>
>> \if SERVER_VERSION_NUM >= xxxx
>> ...
>> \endif
>>
>
> Note that this can already be done by relying on server-side expressions:
>
> SELECT :SERVER_VERSION_NUM >= 110000 AS "version_11_plus" \gset
> \if :version_11_plus
> ...
> \endif
>
> Not very elegant, but functional. I'm not sure there is a compelling
> reason to have this feature beyond elegance.
>

not elegant, not readable, and not user friendly.

the possibility of simple expression evaluation is just practical.

Regards

Pavel

> --
> Fabien.
>