[OSM-dev] Postgres/PostGIS + OSM newbie questions
igor.brejc at gmail.com
Sun Sep 20 21:08:08 BST 2009
For the past few days I've been experimenting with PostGIS, trying to
create some basic support for it from Kosmos. I've managed to setup the
DB, import the UK data and even had some moderate success with accessing
the data from Kosmos code.
Since I'm not very good at SQL (having to relearn tips & tricks every 6
months or so) and I'm totally new to spatial queries, I'm having some
practical problems with retrieving data.
For example, I'm trying to fetch a list of OSM ways (and its nodes) for
a certain area, so that all of ways which have at least one node within
an area appear in the results. And, at the same time, all of the nodes
of such ways should be listed too (regardless of whether a node is
within the area or not).
My current query only returns nodes within the area (so I don't get a
complete list of way's nodes):
way_tags.way_id = ways.id AND
way_nodes.way_id = ways.id AND nodes.id = way_nodes.node_id AND
nodes.geom && SetSRID('BOX(15.556640625 46.4983922585976,15.64453125
46.5588603031172)'::box2d,-1) ORDER BY ways.id, sequence_id')
I'm probably doing this totally wrong, so I have some general questions:
* should I be doing things differently?
* are temporary tables a good option for complex queries (from the
performance point of view)?
* is there some good + open source of example PostGIS queries
specific to OSM data schema (the simple one)?
Any help would be greatly appreciated.
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