[GRASS-user] v.edit tool=delete

[Hamish]

Martin wrote:
> currently `v.edit` does not modify linked attribute tables
> when deleting features, eg.
> 
> $ v.edit map=a tool=delete cat=1
> $ v.db.select a where="cat=1" -c | wc -l
> 1
> 
> I am not sure if this behaviour is preferred from user POV.
> Would you prefer
> 
> 1) to keep current behaviour
> 2) delete attributes when deleting features automatically
> 3) delete attributes only optionally (eg. tool=deleteattr"
> or special flag).

my 2c:

-a flag is a good idea.
-be non-destructive by default.
-for backwards compatibility of behaviour with gr6 probably 'don't delete'
would have to be the default.
-if it deleted by default in grass7 make the flag a different letter to
avoid destroying data by bad assumptions or reusing an old gr6 script.


does v.edit actually delete the line feature or just tag them as "dead"?

 
> Similarly for `tool=add` which do not add new record to the
> table.

note that some maps do not have categories on purpose, and when adding
there are many options (next not used, certain value, step size, etc).
no point in stuffing all of v.category's functionality into v.edit.
Keep It Simple and Stupid.


In a way it depends on your view of what v.edit should be. Is it a do-one-
thing well low-level coordinate-feature editor, or is the fat swiss army
knife with the magnifying glass and the kitchen sink? (not sure if that
phrase translates from english well :)


editing maps in place scares me a bit as you are in trouble if something
goes wrong, so I tend to use the multistep process even if it is a bit
annoying to have a long chain of in=a out=b in=b out=c in=c out=d +
g.remove at the end.   .... save the edits in a version control way
(e.g. temporal property line changes where you want to keep a record of
what changed, who changed it, when, etc) would be a hugely hugely
important feature to add to GRASS, but it would take a lot of work.
Can PostGIS work in a transactional database + change history way?
[I digress but that idea is very important, big demand is out there for
it, and I've been meaning to write about it for a while....]


best,
Hamish