From: Sandro Santilli <strk@keybit.net>
Date: Fri, 13 Apr 2012 21:04:15 +0000 (+0000)
Subject: fix ST_SymDifference(empty, geom) to return geom (#1776)
X-Git-Tag: 2.0.1~131
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=5a74e2c988ff9a1c6d1c151c02e4bcd865fa7dd3;p=postgis

fix ST_SymDifference(empty, geom) to return geom (#1776)

git-svn-id: http://svn.osgeo.org/postgis/trunk@9641 b70326c6-7e19-0410-871a-916f4a2858ee
---

diff --git a/NEWS b/NEWS
index cfc0c8f43..d59a719d2 100644
--- a/NEWS
+++ b/NEWS
@@ -3,6 +3,7 @@ PostGIS 2.0.1
 
 * Bug Fixes *
 
+  - #1776, fix ST_SymDifference(empty, geom) to return geom
   - #1708, improve restore of PosgreSQL 9.1 backups 
   - #1766, don't let ST_RemEdge* destroy peripheral TopoGeometry objects.
   - #1714, more robust handling of high topology tolerance.
diff --git a/liblwgeom/lwgeom_geos.c b/liblwgeom/lwgeom_geos.c
index fdf0c9f14..149ea926c 100644
--- a/liblwgeom/lwgeom_geos.c
+++ b/liblwgeom/lwgeom_geos.c
@@ -583,9 +583,9 @@ lwgeom_symdifference(const LWGEOM* geom1, const LWGEOM* geom2)
 	if ( lwgeom_is_empty(geom2) )
 		return lwgeom_clone(geom1);
 
-	/* Empty.DymDifference(B) == Empty */
+	/* Empty.DymDifference(B) == B */
 	if ( lwgeom_is_empty(geom1) )
-		return lwgeom_clone(geom1);
+		return lwgeom_clone(geom2);
 
 	/* ensure srids are identical */
 	srid = (int)(geom1->srid);
diff --git a/regress/tickets.sql b/regress/tickets.sql
index eaa133e89..75b4356fa 100644
--- a/regress/tickets.sql
+++ b/regress/tickets.sql
@@ -657,5 +657,13 @@ DROP table eg;
 -- #1755 --
 select '#1755', st_geographyFromText('SRID=4326;Point(85 35 0)');
 
+-- #1776 --
+with inp as ( SELECT 
+ 'POLYGON EMPTY'::geometry as A,
+ 'POLYGON((0 0, 10 0, 10 10, 0 0))'::geometry as B )
+SELECT '#1776',
+ ST_AsText(ST_SymDifference(A,B)), ST_AsText(ST_SymDifference(B, A))
+FROM inp;
+
 -- Clean up
 DELETE FROM spatial_ref_sys;
diff --git a/regress/tickets_expected b/regress/tickets_expected
index bab85102f..cb13d9acb 100644
--- a/regress/tickets_expected
+++ b/regress/tickets_expected
@@ -215,3 +215,4 @@ NOTICE:  SRID value -1 converted to the officially unknown SRID value 0
 #1697.3|1024
 #1734.1|1026
 #1755|01010000A0E6100000000000000040554000000000008041400000000000000000
+#1776|POLYGON((0 0,10 0,10 10,0 0))|POLYGON((0 0,10 0,10 10,0 0))