[OSM-dev] Questions regarding carto 4.0 release and German style fork

Sven Geggus lists at fuchsschwanzdomain.de
Sun May 28 19:05:08 UTC 2017


looking at the Openstreetmap Carto 4.0  release I see two major changes
regarding the database layout.

1. We finally have hstore
2. Tags are pre-processed by a lua script.

Is there more which might be relevant for the fork?

Up till know Mapnik German style (an Openstreetmap Carto fork) has been
using an hstore-only database with no sepearte tag columns at all and a
database view emulationg the column based layout.  Upstream style has always
been usable using this approach.

With the recent introduction of hstore in upstream this setup will get more
complicated.  Especially the l10n code is currently dependent on the fact,
that all name tags are present inside the hstore column.

However this can be changed and looks like a manageable approach.

So the question I have to answer for myself now is if it would be worth the
effort working in a direction to be able to use an unchanged database layout
from upstream style.

For this reason I need to know, what the lua script is doing to make shure,
that nothing is processed in a way which will alter the appearance of my

So can somebody please explain in a few words what the lua script is actually

Sorry, I am neither familiar with lua nor ist osm2pgsql interface.

I suspected it might prevent me from redering mountain paths in a different
way than footways, but as far as I can see this is not the case.



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