I've imported the planet (140101.osm.pbf) with hstore support, ran a test render and the results are in.
TL;DR: It works, see attached map of Contern, Lu
I built the latest dev version of osm2pgsql from its sources and ran it with the following parameters: time osm2pgsql -c -s -d maposmatic-hstore -m -U maposmatic -W -H localhost --hstore -C 24576 --number-processes=6 planet-140101.osm.pbf
Because it was still taking too long, I cut the import short after about a day, tuned Postgres and restarted it. After that it ran more than twice as fast. In the end it still took 2.5 days for the import to finish.
Important to note, the database takes up 434GB of diskspace. Whether this is doable on the current maposmatic.org server I don't know. Mind you, to speed up the import I disabled autovacuum, so part of this space can undoubtedly be reclaimed.
A few more things to do for part 2:
- Import a smaller extract (say just The Netherlands) with and without hstore, to figure out the difference in import time and disk space.
- Try and add the HOTOSM style and see if it works now there's hstore support.
- Get this planet's updates running, with hstore support.
- Document the build process used in all of the above.