I have a shape (its topology is terrible but I don't think it's the problem).  I'm trying to simplify it to reduced it's size using `v.generalise`.  I succeeded at reducing the whole shape but I actually want to do a two steps simplification:

 1. simplifying all the shape with threshold 0.0001 first, 
 2. simplifying all the polygons with `urban=0` further more with threshold 0.0003

The problem is that my second `v.generalize` call simplifies everything, like if the `WHERE` call wasn't working.  

For this question, we will just focus on the point 2, so here what I do:

A subset of my data can be found [here][1]. 


And here is some visualization of what I did:

My shape initially:

[![enter image description here][2]][2]

My `v.generalize` call:

[![enter image description here][3]][3]

The result (below) show the blue line the new polygons border which where simplified even if they were not in `urban=0`.

[![enter image description here][4]][4]


Just like if the `WHERE` statement was ignore.  I don't see any error in the log specific to that SQL statement.  The actual call to GRASS built by QGIS is:

    C:\OSGEO4~1\bin>v.generalize input=vector_5be4482a0b8e72 type="line,boundary,area" where="urban=0" method="douglas" threshold=0.0003 look_ahead=7 reduction=50 slide=0.5 angle_thresh=3 degree_thresh=0 closeness_thresh=0 betweeness_thresh=0 alpha=1 beta=1 iterations=1 -l output=output96039149be394bdaa48a3ba7d8b849f7 error=error96039149be394bdaa48a3ba7d8b849f7 --overwrite 

I've try multiple `WHERE` statement (`urban="0"`, `urban<1`, etc) to try to match the `v.generalise` [tutorial][5] but still no luck.  I also tried to do it directly in GRASS bypassing QGIS and the problem persist meaning is not a QGIS problem more than a GRASS problem.

Any idea what the problem is?


  [1]: https://www.dropbox.com/sh/g5x2aw5pmdumqtn/AABfT1aqjdiKnru1cOC_tCp3a?dl=0
  [2]: https://i.sstatic.net/NROjB.png
  [3]: https://i.sstatic.net/eHZdr.png
  [4]: https://i.sstatic.net/zsqNp.png
  [5]: https://grasswiki.osgeo.org/wiki/V.generalize_tutorial#Gereneral_Parameters