Re: BUG #15904: ERROR: argument of LIMIT must not contain variables

Thank you for the clarification and for the time you gave me.

I was convinced of that kind of answer, I still wanted to try, on a
misunderstanding you never know !
I will find a workaround, however the LIMIT_TILL clause would have been
welcomed in this particular case.

Wishing you an excellent weekend.
Marwan L.

Le jeu. 11 juil. 2019 à 18:45, David G. Johnston <david(dot)g(dot)johnston(at)gmail(dot)com>
a écrit :

> On Thu, Jul 11, 2019 at 9:26 AM Lakradi Marwan <lakradimarwan(at)gmail(dot)com>
> wrote:
>
>> Thank you for your quick feedback,
>>
>> In my opinion, your query should return :
>> Id, Text
>> 1| 1, 'one'
>>
>> and be interpreted as due to variable type :
>> LIMIT CASE WHEN 1 = 1 THEN 1 ELSE 2 END;
>>
>> Am I wrong in the way I see the situation ?
>>
>> I think that in the case of a variable, the data should be retrieved
>> until the condition is reached. Like LIMIT_TILL {condition}
>>
>
> That's not an unreasonable expectation. But that isn't how LIMIT is
> defined. LIMIT provides a query result max record count to return to the
> client - mostly to facilitate pagination when used in concert with ORDER BY
> (for determinism) and OFFSET (to skip already seen records). That max is a
> constant determined at plan time which means it cannot rely upon any of the
> data the query itself may generate.
>
> SQL is set oriented and your expectation is incompatible with that
> fundamental property of the system. If you don't want records "after"
> something you need to apply a inequality filter in the WHERE clause to
> remove the undesired records.
>
> David J.
>
>