[Qgis-developer] How should the dissolve tool in Processing work?

Matthias Kuhn matthias at opengis.ch
Mon Oct 19 08:38:19 PDT 2015


On 10/19/2015 05:11 PM, Anita Graser wrote:
> Hi Victor,
> On Mon, Oct 19, 2015 at 1:15 PM, Victor Olaya <volayaf at gmail.com
> <mailto:volayaf at gmail.com>> wrote:
>     Hi Anit
>     ​a​
>     nice discussion you bring up
>     Shouldn't it behave like the ftools dissolve tool currently does?
> ​Yes, it used to behave exactly like ftools still does. But the
> arguments behind the latest changes to the script are that the (ftoos)
> behavior is not what users expect.

The current behavior is not deterministic and therefore in the long run
probably not the most desirable behavior. Reading Bernhard's comments in
the issue, it's quite hard to improve without considerably extending
parameter handling in processing.

Best solution IMO:

 * Keep the current/old behavior for the moment
 * Add new parameter possibilities (e.g. a table/array of string
(attribute name) -> combobox (aggregate function) mappings)
 * Use the current behavior as default setting for fields where the
aggregate funtion is undefined

+ Full backwards compatibility
+ Full control (/as soon as it gets done)
+ One tool for one job (as opposed to "old dissolve" vs. "new dissolve"
- The default behavior may not be optimal (Can still be changed for 3.0
if it's considered to be better)

-- Matthias
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