[Tagging] [OSM-talk] OpenStreetMap Carto release v4.25.0

[Christoph Hormann]

On Wednesday 05 February 2020, Andy Townsend wrote:
> [...]
>
> Basically it's saying "if something is mapped as a brewery and also
> as tourist attraction, remove the tourist attraction tags prior to
> rendering so the renderer renders it as a brewery, not a tourist
> attraction".
>
> Obviously a decision has to be made which of the two tags to render
> if either potentially could - either by layer order or by explicitly
> ensuring that one does and one doesn't, which I've done here.

But that is not the problem here - barriers are rendered after the 
landcover layer both in the past and now.

There is no technical difficulty in doing what Jeroen wants to do by 
re-adding a separate area-barriers layer with something like 

(SELECT way,
    barrier
  FROM planet_osm_polygon
  WHERE (barrier IN ('hedge')
    AND tags->'area' IN ('yes')
    AND osm_id > 0
    AND building IS NULL
) AS area_barriers

and adding a condition to the polygon subquery of the barriers layer 
along the lines of

NOT (barrier IN ('hedge')
  AND tags->'area' IN ('yes')
  AND osm_id > 0)

- in other words:  Special casing exactly the situation in question to 
be treated as an exception.  But that is not in any way sustainable and 
it would be highly confusing for mappers because the conditions 
resulting in this rendering would be unique and could not be derived 
from any general principles.  Mappers would rightfully ask:

* why does turning a closed way tagged barrier=hedge + area=yes into a 
multipolygon releation (for adding an interior ring) change rendering?
* why does removing the unnecessary area=yes from a closed way tagged 
barrier=hedge + area=yes + leisure=playground change the rendering?

-- 
Christoph Hormann
http://www.imagico.de/