[Feat] v.dissolve on more than one attribute columns

[DeyanVasilev]

I have an issue with v.dissolve joining together river polygons. The polygons have a "type" attribute which says "river" and this is the column that I run v.dissolve against to decide to dissolve common boundaries or not. I must dissolve these polygons because of the way river polygons get created - manually in adjacent small pieces several hundred meters long.

Some of the river polygons have a "name" attribute that is obviously targeted at a particular river only. When joining these polygons on the "type" attribute, v.dissolve propagates also the name of the main tributary to all dissolved unnamed minor tributaries part of the same network. This "effect" causes a catastrophe at the map level as wrong names appear sometimes tens of kilometers away from the main tributary and are difficult to trace and fix in general.

There is a resolution of this issue, though it is a complex one: e.g. joining attributes in a new column and then dissolving with the implication how one will restore the original name of the dissolved polygon network.

A much easier workaround would be if v.dissolve gets changed to allow dissolve on more than one attributes, in my case "type" AND "name". This way all named polygons with the same name, unnamed inclusive, will be joined in proper clusters without messing up the names.

Screenshots can be provided to better illustrate the issue, if needed.

[wenzeslaus]

Thank you. While your description seems pretty good from a casual read, screenshot is always appreciated, especially of the desired solution. Even better is some kind of step by step process which shows input and desired output.