Re: Drop one-argument string_agg? (was Re: [BUGS] string_agg delimiter having no effect with order by)

On Thu, Aug 5, 2010 at 3:16 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Josh Berkus <josh@agliodbs.com> writes:
>>> Well, maybe we need to expend some more sweat on the error message then.
>>> But this patch was still a prerequisite thing, because without it there
>>> is no error that we can complain about.
>
>> Yes, I'd say an addition to the HINT is in order *assuming* at that
>> stage we can tell if the user passed an ORDER BY or not.
>
> I was just looking at this, and realized I was mistaken earlier: the
> error is issued in ParseFuncOrColumn, which already is passed the
> agg_order list, so actually it's completely trivial to tell whether
> a variant error message is appropriate.  I suggest that we key it off
> there being not just an ORDER BY, but an ORDER BY with more than one
> element; if there's only one then this cannot be the source of
> confusion.
>
> Next question: exactly how should the variant HINT be phrased?
> I'm inclined to drop the bit about explicit casts and make it read
> something like
>
> HINT: No aggregate function matches the given name and argument
> types. Perhaps you misplaced ORDER BY; ORDER BY must appear after all
> regular arguments of the aggregate.

Could we arrange to emit this error message only when there is an
aggregate with the same name but different arguments?

--
Robert Haas
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