[postgis-devel] [PostGIS] NULL-values ar function arguments

[Paul Ramsey]

The argument is that 'null' does not mean 'empty' or 'nothing' it
means undefined. So trimming something by undefined yields undefined.

P.

On Wed, Jun 29, 2011 at 3:31 PM, Nicklas Avén
<nicklas.aven at jordogskog.no> wrote:
> We have a wiki-page and discussion about EMPTY GEOMETRIES
>
> should we have something corresponding about handling of NULL-values?
>
> I just opened #1078 about NULL-values as second argument in
> ST_Difference
>
> In ST_Collect we return the not null values
>
> Other functions I have checked returns NULL if a null-value is involved.
>
> I think this is specially interesting incases when you use left or right
> join like in the gis.stackexchange question that lead to my ticket:
> http://gis.stackexchange.com/questions/11592/difference-between-two-layers-in-postgis
>
>
> In the ticket Paul gives the example of btrim('this', NULL) which also
> returns NULL instead of 'this' as I would expect.
>
> What is the arguments for this behavior?
>
>
> Regards
>
> Nicklas
>
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