[libdbi-devel] Re: [libdbi-users] stupid question about nulls

[Christian S. <chr...@ce...>]

Hello again,

Guess you are using the function 
dbi_result_get_field_length( )   which today return size-1 for some reason.

You could use: 
dbi_result_get_field_size( )  which returns the accual value. 

But I guess these functions would need to be tweaked to fit in with this new 
behaviour. 
The right (clean) way  of doing things would be to implement 
dbi_result_field_isnull() or simular to check if a field is null.
That way we could change the internals of libdbi without changing all 
applications that was hacked to check if size was -1. It will also make it 
more obvious what happens.   

Regards,

//Christian


On Thursday 29 July 2004 15.14, m.e...@ls... wrote:
> Thanks Christian! I didn't even think of looking at the length...
>
> I only have pqsql, but it looks as if for this one at least the length
> is always 0 except for strings, where it is equal to the length of the
> string (as you say it does not seem to implement what's in the comment).
>
> I tried implementing your suggestion myself in dbd_pgsql.c, and got as
> far as
>
> 512a513
>
> >                       row->field_sizes[curfield] = -1;
>
> Unfortunately, now I get a length of -2 for NULLs???
>
> Maybe someone familiar with the driver could have a look at this? It
> would be neat to be able to distinguish between NULL, "" and 0...
>
> Max
>
> On Thu, 2004-07-29 at 12:41, Christian Stamgren wrote:
> > Hello.
> >
> > I belive this is a short comming of the libdbi-drivers as it looks today.
> >
> > By reading dbi-dev.h you will find this row part of dbi_row_t struct.:
> >
> > unsigned long long *field_sizes; /* NULL field = 0, string field = len,
> > anything else = -1 */
> >
> > But the drivers does not implemet it this way.
> >
> >
> > I'll suggest that we change it so that:
> > NULL field = -1, string field = len, anything else = 0
> >
> > That way we will have distinction between NULL and a string of 0 chars
> > (which is not the same as NULL).
> >
> > It would then be easy to implement a couple of funtions like:
> >
> > dbi_result_field_isnull(result, "fieldname");
> > or
> > dbi_result_field_isnull_idx(result, 2);
> >
> >
> >
> > Regards,
> >
> > //Christian
> >
> > On Wednesday 28 July 2004 15.45, m.e...@ls... wrote:
> > > Hi,
> > >
> > > I have been running some queries that return NULLs at times (in fields
> > > that contain doubles).
> > >
> > > It looks as if you use dbi_result_get_double() you get 0 whenever the
> > > query returned a NULL.
> > >
> > > How can I distinguish between a NULL and 0? It looks like I might have
> > > missed something obvious here...
> > >
> > > Thanks,
> > >
> > > Max
> > >
> > >
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