How to find a line/edge that starts at the same point as the end of another

Question

I have an edges table of Lat/Lon data and for a specific edge I want to find any other edges that have the same start point as the end point of the given edge.
I tried the following query:
select geo_street_id from geo_street s2
where SDO_LRS.GEOM_SEGMENT_START_PT(s2.geom) =
(select SDO_LRS.GEOM_SEGMENT_END_PT(s.geom) as geom from geo_street s
where geo_street_id = 122978214)
but it gets the following error:
ORA-22901: cannot compare nested table or VARRAY or LOB attributes of an object type
Any Ideas?

Answer 1

1. to compare geometry to be equal you should use appropriate function (SDO_GEOM.RELATE http://download.oracle.com/docs/html/B14255_01/sdo_objgeom.htm#sthref1561) or operators (sdo_relate http://download.oracle.com/docs/html/B14255_01/sdo_operat.htm#i78531) with specific mask EQUAL.
2. to filter down the resultset in first place you can use the operator SDO_RELATE with mask TOUCH as this will return already the set of lines sharing endpoints, but will also include lines touching eachother not at endpoints (endpoint intersecting the otherone's interior)
something like
select geo_street_id from geo_street s2, geo_street s
where
s.geo_street_id = 122978214
AND
sdo_relate(s2.geom, s.geom,'mask=touch') = 'TRUE'
AND
sdo_geom.relate(SDO_LRS.GEOM_SEGMENT_START_PT(s2.geom),
'EQUAL',
SDO_LRS.GEOM_SEGMENT_END_PT(s.geom),0.005)='EQUAL'
3. if you would do this for the full table, an SDO_JOIN (http://download.oracle.com/docs/html/B14255_01/sdo_operat.htm#BGEDJIBF) might be more appropriate.
4. you might also consider 4 cases:
start = start
start = end
end = start
end = end
5. alternative would be to take only the endpoints of your selected geometry and perform a touch with the edges. using the sdo_util.APPEND on the startpoint en endpoint of your geometry will return a multipoint. although there might some specific cases that this would not return respected result I think
something like:
select geo_street_id from geo_street s2, geo_street s
where
s.geo_street_id = 122978214
AND
sdo_relate(s2.geom,
SDO_UTIL.APPEND(
SDO_LRS.GEOM_SEGMENT_START_PT(s.geom),
SDO_LRS.GEOM_SEGMENT_END_PT(s.geom)
,'mask=touch') = 'TRUE'
Let us know how it works.
Luc