Re: AW: Overloaded UDF

[Simon Coulter <shc@xxxxxxxxxxxxxxxxx>]

On 03/12/2009, at 10:59 AM, Scott Klement wrote:

> I can't imagine that it reads your program's source code to determine
> this.  There's no way from outside of the procedure to know what
> parameters it can potentially take.
>
> (Yes, I know about the ability to generate PCML and store it in a
> module, but SQL isn't using that functionality because that
> functionality is MUCH newer than UDF capability, and it's not always
> there, so that support is clearly not used.)
>
> Since SQL can't know about this extra parameter, it can't know that it
> has to set the pointer to zeros...  I can't see how Birgitta could be
> right.  The only way it would make sense is if SQL always sets a
> predefined number of pointers (maybe 399?) to *NULL... but that  
> doesn't
> seem likely to me, as that 24k of x'00' would be a fairly expensive
> operation, and it's inconsistent with the way this parameter info is
> filled in everywhere else.

If SQL does determine the maximum number of parameters then I would  
expect it does so by interrogating the information in SYSPROCS. This  
has the function name and number of parameters. It would be possible  
to query this file for the maximum number of parameters for a given  
function name and ensure at least that many parameters were passed by  
supplying a null pointer for any missing ones. That would be a far  
more likely approach than relying on source code (which likely is not  
on the production system anyway) or using PCML information.

However, I strongly doubt SQL does any such thing and that the  
presence of a null pointer for omitted parameters is simply  
happenstance.

It would be nice to know definitively whether SQL does handle this in  
a predictable manner because the ability to have a single program or  
procedure implement overloaded functions would be useful.

Regards,
Simon Coulter.
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