[Qgis-user] Attribute "cat" in grass7

[Benjamin Ducke]

Hi --

On 19/12/2018 20:40, Roberto Herrero wrote:
> I've seen that the grass7 algorithms add an extra attribute called
> "cat". I wonder if the behaviour of the algorithms can be modified not
> to show that attribute.

"cat"(egory) is an integer index that serves
as primary key for all GRASS vector modules.
It is automatically added as soon as data is
imported into GRASS. If "cat" exists in an
external dataset then GRASS will attempt to
rename it to "_cat". If that also fails, GRASS
will abort with an error.

So the GRASS algorithm provider in QGIS would
have to jump through quite some hoops in order
to make sure that "cat" (or "_cat") is only
removed if it does not exist in the input data
that is passed to GRASS. It would also have to
make sure that an attribute "cat" is not the user-
intended outcome of a GRASS process.

In addition, some GRASS commands work explicitly
on "cat" and refer to it on the manual page.

I think rather than worrying about all of that I
would just ignore "cat" or manually delete that
column from result data.

Best,

Ben


> 
> Thank you,
> Roberto Herrero
> 
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-- 
Dr. Benjamin Ducke
Deutsches Archäologisches Institut (DAI)
Zentrale Berlin, IT-Referat
* Projekt "Stunde Null" *