ST_Subdivide: support rect hole in rect shell

Closes #4211
Closes #317


git-svn-id: http://svn.osgeo.org/postgis/branches/2.5@16938 b70326c6-7e19-0410-871a-916f4a2858ee

NEWS

@@ -8,7 +8,8 @@ XXXX/XX/XX
   - #4191, Fix undefined behaviour in ptarray_clone_deep (Raúl Marín)
   - #4020, Fix leftovers in topology upgrade from 2.1 (Sandro Santilli)
   - #4206, Fix support for PostgreSQL 12 dev branch (Laurenz Albe)
-
+  - #4211, Fix ST_Subdivide for minimal exterior ring with minimal hole (Darafei
+    Praliaskouski)
 
 PostGIS 2.5.0
 2018/09/23

liblwgeom/lwgeom.c

@@ -2353,7 +2353,7 @@ lwgeom_subdivide_recursive(const LWGEOM *geom, uint8_t dimension, uint32_t maxve
 		lwpoly = (LWPOLY *)geom;
 
 		/* if there are more points in holes than in outer ring */
-		if (nvertices > 2 * lwpoly->rings[0]->npoints)
+		if (nvertices >= 2 * lwpoly->rings[0]->npoints)
 		{
 			/* trim holes starting from biggest */
 			for (i = 1; i < lwpoly->nrings; i++)

regress/subdivide.sql

@@ -58,3 +58,5 @@ FROM big_polygon_sliced gs;
 
 drop table big_polygon;
 drop table big_polygon_sliced;
+
+select '#4211', (select sum(ST_Area(geom))::numeric(12,11) from ST_Subdivide('MULTIPOLYGON(((-88.2059 41.7325,-88.2060 41.7244,-88.1959 41.7241,-88.1959 41.7326,-88.2059 41.7325),(-88.1997 41.7289,-88.1996 41.7285,-88.1990 41.7285,-88.1990 41.7289,-88.1997 41.7289)))') geom );

regress/subdivide_expected

@@ -5,3 +5,4 @@ ERROR:  lwgeom_subdivide: cannot subdivide to fewer than 5 vertices per output
 #3522|POINT(1 1)
 #3744|1600000000000000
 4|29321996468.6|29321996468.6|1857|256
+#4211|0.00008316000