[Tile-serving] [osm2pgsql] Change z_order of link roads and add tests (#374)

[math1985]

The proposed code looks good.

I'd still consider also including z_order for railways. Anyone who wants to order roads and railways properly and who does not want to create 11 layers in the .mml-file for all layers -5 to 5, will have roads and railways in one layer, so the ordering of railways must be set somewhere. The UNION BY is only necessary for these renderings that cover areas that have trams and highways sharing objects. If necessary, renderers could manually exclude trams from the layer (on the cost of ordering problems), like in the old default Mapnik layer, so the UNION BY is not necessary. Anyway I think defining order for railways is useful for many users, and won't harm others.

I'd also include highway=proposed and highway=construction.

---
Reply to this email directly or view it on GitHub:
https://github.com/openstreetmap/osm2pgsql/pull/374#issuecomment-119373853
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.openstreetmap.org/pipermail/tile-serving/attachments/20150707/6c3600a9/attachment.html>