Sdo_union gives inconsistent results

Question

Hi,
Oracle Database 10g Enterprise Edition Release 10.2.0.4.0
We are using sdo_union to convert line geometries. Some of the geometries that are inserted into our database have sdo_gtype 2006, but can be easily converted to 2002 using a query like:
update lines_tb l
set    shape = case when sdo_geom.sdo_union(l.shape, l.shape, 0.001).sdo_gtype = 2002
                    then sdo_geom.sdo_union(l.shape, l.shape, 0.001)
                    else l.shape
               end
where  l.shape.sdo_gtype = 2006;We notice however that if you run the query again, it keeps finding results! It does not make any sense...
The only conslusion I can make is that sdo_union is not consistent in its results!
Can anyone confirm this behaviour?
Thanks,
Rop

Answer 1

Here's an example that shows the issue:
with g as ( select sdo_geometry(2006,31370,sdo_point_type(null,null,null),
                   sdo_elem_info_array( 1,2,1,7,2,1,15,2,1,53,2,1,61,2,1),
                   sdo_ordinate_array( 63634.1550000012,183385.377799999,63638.9395999983,183373.2269,63641.8335999995,183365.5623,63634.1550000012,183385.377799999,63634.1600999981,
                                       183385.3662,63634.1458000019,183385.400899999,63634.1550000012,183385.377799999,63632.0187999979,183387.558600001,63632.0841000006,183387.529199999,
                                       63632.2485999987,183387.4463,63632.4094000012,183387.356400002,63632.5659999996,183387.259599999,63632.7184000015,183387.156100001,63632.8660999984,
                                       183387.046100002,63633.0088,183386.9298,63633.1463999972,183386.807300001,63633.2780999988,183386.679499999,63633.4047999978,183386.545499999,63633.5253999978,
                                       183386.406199999,63633.6398999989,183386.261799999,63633.7479000017,183386.112599999,63633.8493999988,183385.958799999,63633.9442000017,183385.800799999,
                                       63634.0319999978,183385.638799999,63634.1125999987,183385.473099999,63634.1550000012,183385.377799999,63632.0187999979,183387.558600001,63632.1538000032,
                                       183387.529800002,63631.9161999971,183387.604800001,63632.0187999979,183387.558600001,63619.0442000032,183388.850099999,63629.3642999977,183388.124699999,
                                       63632.0187999979,183387.558600001 )) geom from dual )
select sdo_geom.sdo_union(g.geom,g.geom, 0.001).sdo_gtype
from   g
,    ( select * from all_tables where rownum <= 100)On our database (10g Enterprise Edition Release 10.2.0.4.0) this will give results like:
2002
2006
2006
2006
2006
...But sometimes it gives only 2002 and other times only 2006...
Edit: All geometries have been validated.