Re: poc - possibility to write window function in PL languages

pá 28. 8. 2020 v 8:14 odesílatel Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>
napsal:

>
>
> st 26. 8. 2020 v 17:06 odesílatel Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>
> napsal:
>
>> Hi
>>
>> I simplified access to results of winfuncargs functions by proxy type
>> "typedvalue". This type can hold any Datum value, and allows fast cast to
>> basic buildin types or it can use (slower) generic cast functions. It is
>> used in cooperation with a plpgsql assign statement that can choose the
>> correct cast implicitly. When the winfuncarg function returns a value of
>> the same type, that is expected by the variable on the left side of the
>> assign statement, then (for basic types), the value is just copied without
>> casts. With this proxy type is not necessary to have special statement for
>> assigning returned value from winfuncargs functions, so source code of
>> window function in plpgsql looks intuitive to me.
>>
>> Example - implementation of "lag" function in plpgsql
>>
>> create or replace function pl_lag(numeric)
>> returns numeric as $$
>> declare v numeric;
>> begin
>> v := get_input_value_in_partition(windowobject, 1, -1, 'seek_current',
>> false);
>> return v;
>> end;
>> $$ language plpgsql window;
>>
>> I think this code is usable, and I assign this patch to commitfest.
>>
>> Regards
>>
>> Pavel
>>
>
> fix regress tests and some doc
>

update - refactored implementation typedvalue type