Re: Window-functions patch handling of aggregates

2008/12/25 Hitoshi Harada <umi(dot)tanuki(at)gmail(dot)com>:
> 2008/12/25 Greg Stark <greg(dot)stark(at)enterprisedb(dot)com>:
>> Yeah, it seems like adding a flag like iswindowable to aggregate functions
>> is the safest option.
>>
>> It would be nice if it represented an abstract property of the state
>> function or final function rather than just "works with the implementation
>> of window functions". I'm not sure what that property is though -
>> isidempotent? isreentrant? Maybe just a vague isrepeatable?
>
> No, I meant wrinting such like:
>
> Datum
> some_trans_fn(PG_FUNCTION_ARGS)
> {
> if (fcinfo->context && IsA(fcinfo->context, WindowAggState))
> elog(ERROR, "some_agg does not support window aggregate");
>
> ...
> }
>
> rather than adding column to catalog. To add flag you must add new
> syntax for CREATE AGGREGATE, which is slightly more painful.
>

enhancing of CREATE AGGREGATE syntax should be better, it could solve
problem with compatibility.

regards
Pavel Stehule

> Regards,
>
> --
> Hitoshi Harada
>
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