# [postgis-users] reparing invalid geometry (polygon defined byoneor two points)

Obe, Regina robe.dnd at cityofboston.gov
Tue Mar 24 05:24:36 PDT 2009

```Ivan,

Oops more of a variant.   I see you have invalid polygons as well not
just rings.  Hmm try this instead.  I didn't check my logic, but
hopefully you get the idea if this doesn't compile.

This is a bit of overkill if you have no multipolys with invalid rings.
But I'll leave as an exercise for you to figure out the simpler variant
if you need it.

CREATE OR REPLACE FUNCTION remove_invalidpoly(geometry)
RETURNS geometry AS
\$BODY\$
SELECT ST_BuildArea(ST_Collect(b.final_geom)) as filtered_geom
FROM (SELECT ST_MakePolygon((/* Get outer ring of polygon */
SELECT ST_ExteriorRing(a.the_geom) as outer_ring /* ie
the outer ring */
),  ARRAY(/* Get all inner rings > a particular area */
SELECT ST_ExteriorRing(b.geom) as inner_ring
FROM (SELECT (ST_DumpRings(a.the_geom)).*) b
WHERE b.path[1] > 0 /* ie not the outer ring */
AND (ST_NPoints(b.geom) > 2 AND ST_IsClosed(b.geom))
) ) as final_geom
FROM (SELECT g.geom As the_geom
FROM ST_Dump(\$1) As g
WHERE ST_NPoint(g.geom) > 2 AND ST_IsClosed(g.geom)
) a
) b
\$BODY\$
LANGUAGE 'sql' IMMUTABLE;

-----Original Message-----
From: postgis-users-bounces at postgis.refractions.net
[mailto:postgis-users-bounces at postgis.refractions.net] On Behalf Of Obe,
Regina
Sent: Tuesday, March 24, 2009 8:14 AM
To: PostGIS Users Discussion
Subject: RE: [postgis-users] reparing invalid geometry (polygon defined
byoneor two points)

Ivan,

I think a variant of Simon's script would work for you except instead of
keeping rings with a large enough hole, keep rings that are closed and
have enough points

n-polygon-postgis

so something like

CREATE OR REPLACE FUNCTION remove_invalidrings(geometry)
RETURNS geometry AS
\$BODY\$
SELECT ST_BuildArea(ST_Collect(b.final_geom)) as filtered_geom
FROM (SELECT ST_MakePolygon((/* Get outer ring of polygon */
SELECT ST_ExteriorRing(a.the_geom) as outer_ring /* ie
the outer ring */
),  ARRAY(/* Get all inner rings > a particular area */
SELECT ST_ExteriorRing(b.geom) as inner_ring
FROM (SELECT (ST_DumpRings(a.the_geom)).*) b
WHERE b.path[1] > 0 /* ie not the outer ring */
AND (ST_NPoints(b.geom) > 2 AND ST_IsClosed(b.geom))
) ) as final_geom
FROM (SELECT ST_GeometryN(ST_Multi(\$1),/*ST_Multi converts any
Single Polygons to MultiPolygons */

generate_series(1,ST_NumGeometries(ST_Multi(\$1)))
) as the_geom
) a
) b
\$BODY\$
LANGUAGE 'sql' IMMUTABLE;

Hope that helps,
Regina

-----Original Message-----
From: postgis-users-bounces at postgis.refractions.net
[mailto:postgis-users-bounces at postgis.refractions.net] On Behalf Of Ivan
Mincik
Sent: Tuesday, March 24, 2009 5:03 AM
To: PostGIS Users Discussion
Subject: [postgis-users] reparing invalid geometry (polygon defined by
oneor two points)

Dear PostGIS users,
we have quite huge MULTIPOLYGON database table containing some 3
percents of invalid geometries.
Most problematic to repair are MULTIPOLYGONs which often contain polygon
defined by one or two points.

Example is here (second polygon is defined by one point):
MULTIPOLYGON(((-266469.87 -1233431.41,-266423.25 -1233425.84,-266423.23
-1233426.17,-266422.74 -1233434.54,-266422.75 -1233439.44,-266425.68
-1233439.9,
-266457.02 -1233444.89,-266463.17 -1233437.07,-266463.27
-1233436.29,-266469.15 -1233437.08,-266469.84 -1233431.65,-266469.87
-1233431.41),(-266463.92 -1233431.02),
(-266459.41 -1233430.46,-266458.67 -1233436.67,-266451.29
-1233435.76,-266451.1 -1233437.26,-266438.9 -1233435.75,-266439.07
-1233434.35,-266426.37 -1233432.65,-266427.07 -1233426.46,
-266439.85 -1233428.04,-266459.41 -1233430.46)))

It is not possible to run buffer(0) or many other functions on these
geometries because of "POSTGIS2GEOS conversion failed" (no suprise in
case of such non-sense geometry).

Is there any possibility how to repair them directly in database?

Thanks
Ivan

_______________________________________________
postgis-users mailing list
postgis-users at postgis.refractions.net
http://postgis.refractions.net/mailman/listinfo/postgis-users
-----------------------------------------
The substance of this message, including any attachments, may be
confidential, legally privileged and/or exempt from disclosure
pursuant to Massachusetts law. It is intended
contact the sender and delete the material from any computer.
_______________________________________________
postgis-users mailing list
postgis-users at postgis.refractions.net
http://postgis.refractions.net/mailman/listinfo/postgis-users
-----------------------------------------
The substance of this message, including any attachments, may be
confidential, legally privileged and/or exempt from disclosure
pursuant to Massachusetts law. It is intended