TopologyException in GEOS ST_Union function
I'm writting a function using the plpgsql language in PostgreSQL.
This function operate with geometries and I do something like this:
-- Open a cursor for a table
OPEN veget_cursor FOR
SELECT gid, wkb_geometry as the_geom
FROM table_v;
LOOP
FETCH veget_cursor INTO _gid, veget_geom;
-- Validate the geometry of the table table_v
IF ST_isvalid(veget_geom) THEN
-- Open a cursor for a selection. The selection only contains the
geometries that intersects
-- with the current geometry of the cursor veget_cursor.
OPEN floor_cursor FOR
SELECT gid, wkb_geometry as the_geom
FROM table_f
WHERE ST_Intersects(wkb_geometry, veget_geom);
LOOP
FETCH floor_cursor INTO f3, floor_geom;
-- Validate the geometry of the other table
(table_f)
IF ST_isvalid(floor_geom) THEN
-- Intersects the geometries of the two
cursors
geom := ST_Intersection(floor_geom,
veget_geom);
-- Validate the resultant geometry of
the intersection operation
IF (ST_Isvalid(geom)) THEN
-- Here join the geometry of geom into
union_geom
IF union_geom IS NULL
THEN
union_geom :=
geom;
ELSE
union_geom :=
st_union(union_geom, geom);
END IF;
END IF;
END IF;
END LOOP;
CLOSE floor_cursor;
END LOOP;
CLOSE veget_cursor;
This code throw a topology exception:
TopologyException: found non-noded intersection between -83.5325
22.7268, -83.5327 22.7271 and -83.5327 22.7269, -83.5325 22.7268
-83.5325 22.7268
ERROR: GEOS union() threw an error!
The questions are:
- Why does it throw an exception if I'm validating all geometries?
- What does the exception mean?
- What can I do?
Best regards, Salas
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