Reporter: bestoujev[at]gmail.com
[Submitted to the original trac issue database at 10.18pm, Tuesday, 5th April 2011]

When a one node way is present in the database and osmosis creates a linestring geometry for it the resulting geometry is something like LINESTRING(139.386972 37.095865)

When we process this linestring with any postgis function it gives us an error - the linestring must contain 0 or > 1 nodes.

When linestring objects are created with internal osmosis functions the number of nodes is checked to be >= 2, but the sql-command does not contain such a check.

I suggest changing the code of WayDao.java from:

private static final String SQL_UPDATE_WAY_LINESTRING =
	"UPDATE ways w SET linestring = ("
	+ " SELECT MakeLine(c.geom) AS way_line FROM ("
	+ " SELECT n.geom AS geom FROM nodes n INNER JOIN way_nodes wn ON n.id = wn.node_id"
	+ " WHERE (wn.way_id = w.id) ORDER BY wn.sequence_id"
	+ " ) c"
	+ " )"
	+ " WHERE w.id  = ?";

to

private static final String SQL_UPDATE_WAY_LINESTRING =
	"UPDATE ways w SET linestring = ("
	+ " SELECT MakeLine(c.geom) AS way_line FROM ("
	+ " SELECT n.geom AS geom FROM nodes n INNER JOIN way_nodes wn ON n.id = wn.node_id"
	+ " WHERE (wn.way_id = w.id) and array_length(nodes, 1) > 1 ORDER BY wn.sequence_id"
	+ " ) c"
	+ " )"
	+ " WHERE w.id  = ?";

the "and array_length(nodes, 1) > 1" code will make sure that there are more than 1 node in this way.

I am not a java programmer, so I am not sure that it is the best solution, but this is surely a workaround for the problem . One node ways do not allow to work with the database properly, so this is a very important issue.