[Maps-l] non-rendering application at the osm-database

[Peter Wendorff]

Hi.
I'm working on the look-and-listen-map (toolserver project lalm), a web 
map portal for the Blind and Visually Impaired.
That is not a rendering application like the several mapnik stylesheets 
running on the toolserver, but I agreed with the Admins, that it might 
be worth in respect of capacities of the toolserver to use the mapnik 
style nevertheless.

Today I finally got database access and looked deeper into the schema. 
Most queries in my application rely on the osm_id present in all tables 
(and index, too), so that's not a problem.
Some queries will later on require geometric queries, but here I can 
combine the postprocessed tables (planet_nodes, planet_line, 
planet_polygon...) for filtering and the non-processed ones for fetching 
the values - so that's okay, too.

My problem lies, where mapnik does ugly tricks for rendering: I have a 
node-id and want to get all ways this node is part of.

That would be possible, querying planet_ways, as planet_ways contains a 
field nodes, that is a integer-array; but as far as I know there is no 
performant way to query an array-field of a database on containing a 
particular element.

Currently my code is based on a different database schema, but I have a 
query with the following characteristics, that I need with the 
osm_mapnik-scheme:

IN: node_id (int)
OUT: a list of way_id, where the corresponding way contains the node 
with id node_id.

A second question would be, if errors would occur, when I combine e.g. 
planet_ways with planet_line in a query, and a matching row in 
planet_ways is pending. Usually the intermediate tables are only 
accessed by the import tool, so I would do unconventional things here, 
but am I right? If the planet_ways-row is pending, the data of this 
table is not in sync with the data in planet_line.

regards
Peter
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