[GRASS-dev] Vect_open_old versus Vect_open_old2 and layer/field constraint

[Vaclav Petras]

On Mon, Sep 28, 2015 at 11:22 AM, Martin Landa <landa.martin at gmail.com>
wrote:
>
> Hi,
>
> 2015-09-28 16:56 GMT+02:00 Vaclav Petras <wenzeslaus at gmail.com>:
>
> [...]
>
> > what is the meaning for native vector maps? Does this limit the layer
as in
> > case of Vect_set_constraint_field() or do I actually have to call
> > Vect_set_constraint_field() to read features only in one layer?
>
> AFAIK currently it has no meaning to native maps, `layer` argument is
> used only by OGR direct access [1].

OK, thanks.

I have an additional question:

When getting field number to be used in Vect_set_constraint_field() and
with categories, should I use Vect_get_field_number()? The doc says "Get
field number of given field" but not when it should be used. I have seen it
in other modules but I'm not sure if this is correct, esp. for direct OGR
access.

> Ma
>
> [1]
https://trac.osgeo.org/grass/browser/grass/trunk/lib/vector/Vlib/open.c#L206
>
> --
> Martin Landa
> http://geo.fsv.cvut.cz/gwiki/Landa
> http://gismentors.cz/mentors/landa
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