[postgis-devel] LINESTRING from A to B to A, bug or feature?

[Sakari A. Maaranen]

I'm developing a data converter from OSM XML to PostGIS database and
testing (visualizing) the data with GeoServer. For test data I'm using
an OSM extract of Malta.

When I import the data and try to view it using GeoServer Preview
Layer function, OpenLayers complains about internal error:
Error rendering feature
null

I managed to trace down the probelm to a single map feature that is
the linestring id=257482 below.

Obviously the problem with that geometry is that it is a closed "ring"
of only two points, back and forth between those points.

It seems that the node id=325699224 is used twice in the OSM way
id=29551661 (sequence numbers 6 and 8 below).

Now I'm not sure where's the bug?

1. Is it a bug in PostGIS JDBC extension that allows creating such a
LineString. Shouldn't it throw an exception?
    I'm using the org.postgis.LineString(Point[] points) constructor
that does not complain.

2. If it's valid geometry, shouldn't OpenLayers be able to render it?

3. Is it a bug in OSM data? Probably not because OSM doesn't have a
very strict specification, and it's legal to use the same node
multiple times.

I will need to work around it anyway... (or fix it, if it's a bug in
my converter that doesn't manage this special case yet.)

Br,

Sakari Maaranen

{{{
routing_test=# select id,way,source,target,astext(geom) FROM
pgrouting_edges WHERE way=29551661;
   id   |   way    |  source   |  target   |
                    astext
--------+----------+-----------+-----------+----------------------------------------------------------------------------------------------------
 257480 | 29551661 | 325699200 | 325699230 | LINESTRING(14.2465489
36.041279,14.2469467 36.0411728,14.2471291 36.041092)
 257481 | 29551661 | 325699230 | 325699224 | LINESTRING(14.2471291
36.041092,14.2473653 36.0409924,14.2474878 36.0409788,14.2475609
36.0409991)
 257482 | 29551661 | 325699224 | 325699224 | LINESTRING(14.2475609
36.0409991,14.2478792 36.0410809,14.2475609 36.0409991)
 257483 | 29551661 | 325699224 | 325699225 | LINESTRING(14.2475609
36.0409991,14.2477134 36.0405635)
(4 rows)


routing_test=# select * from osm_way_nodes where id=29551661;
    id    |    nd     | sequence
----------+-----------+----------
 29551661 | 325699200 |        1
 29551661 | 325699220 |        2
 29551661 | 325699230 |        3
 29551661 | 325699221 |        4
 29551661 | 325699222 |        5
 29551661 | 325699224 |        6
 29551661 | 325699223 |        7
 29551661 | 325699224 |        8
 29551661 | 325699225 |        9
(9 rows)


routing_test=# select k,v from osm_way_tags where id=29551661;
    k    |        v
---------+------------------
 source  | Yahoo;gps;survey
 highway | service
(2 rows)
}}}