<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=ISO-8859-15">
</head>
<body bgcolor="#FFFFFF" text="#000000">
<div class="moz-text-flowed" style="font-family: -moz-fixed;
font-size: 14px;" lang="x-western">Hi.
<br>
I'm working on the look-and-listen-map (toolserver project lalm),
a web map portal for the Blind and Visually Impaired.
<br>
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.
<br>
<br>
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.
<br>
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.
<br>
<br>
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.
<br>
<br>
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.
<br>
<br>
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:
<br>
<br>
IN: node_id (int)
<br>
OUT: a list of way_id, where the corresponding way contains the
node with id node_id.
<br>
<br>
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.
<br>
<br>
regards
<br>
Peter
<br>
</div>
</body>
</html>