From 17f6c5c0c87fe0d8dbcdd4476f22df60a7e000d6 Mon Sep 17 00:00:00 2001
From: Darafei Praliaskouski <me@komzpa.net>
Date: Tue, 5 Jun 2018 14:40:45 +0000
Subject: [PATCH] Unify geometry centroid functions

Make ST_Centroid call lwgeom_centroid.

Closes #3960
Closes https://github.com/postgis/postgis/pull/256



git-svn-id: http://svn.osgeo.org/postgis/trunk@16608 b70326c6-7e19-0410-871a-916f4a2858ee
---
 NEWS                   |  8 ++---
 postgis/lwgeom_geos.c  | 68 ++++++------------------------------------
 postgis/postgis.sql.in |  1 -
 3 files changed, 12 insertions(+), 65 deletions(-)

diff --git a/NEWS b/NEWS
index 947a8b2be..eeb88139d 100644
--- a/NEWS
+++ b/NEWS
@@ -51,10 +51,8 @@ PostGIS 2.5.0
   - #3097, Really allow MULTILINESTRING blades in ST_Split() (Paul Ramsey)
   - #3942, geojson: Do not include private header for json-c >= 0.13 (Björn Esser)
   - #3954, ST_GeometricMedian now supports point weights (Darafei Praliaskouski)
-  - #3965, ST_ClusterKMeans used to lose some clusters on initialization
-           (Darafei Praliaskouski)
-  - #3971, ST_ClusterKMeans now uses better initial seed (Darafei Praliaskouski)
-  - #3977, ST_ClusterKMeans is now faster and simpler (Darafei Praliaskouski)
+  - #3965, #3971, #3977, #4071 ST_ClusterKMeans rewritten: better initialization,
+           faster convergence, K=2 even faster (Darafei Praliaskouski)
   - #3982, ST_AsEncodedPolyline supports LINESTRING EMPTY and MULTIPOINT EMPTY
            (Darafei Praliaskouski)
   - #3986, ST_AsText now has second argument to limit decimal digits
@@ -72,13 +70,13 @@ PostGIS 2.5.0
            robustness issues. (Darafei Praliaskouski)
   - #4025, #4032 Fixed precision issue in ST_ClosestPointOfApproach,
            ST_DistanceCPA, and ST_CPAWithin (Paul Ramsey, Darafei Praliaskouski)
-  - #4071, ST_ClusterKMeans crash on NULL/EMPTY fixed (Darafei Praliaskouski)
   - #4076, Reduce use of GEOS in topology implementation (Björn Harrtell)
   - #4080, Add external raster band index to ST_BandMetaData
   - Add Raster Tips section to Documentation for information about
     Raster behavior (e.g. Out-DB performance, maximum open files)
   - #4084: Fixed wrong code-comment regarding front/back of BOX3D (Matthias Bay)
   - #4060, #4094, PostgreSQL JIT support (Raúl Marín, Laurenz Albe)
+  - #3960, ST_Centroid now uses lwgeom_centroid (Darafei Praliaskouski)
 
 PostGIS 2.4.4
 2018/04/08
diff --git a/postgis/lwgeom_geos.c b/postgis/lwgeom_geos.c
index 2e91b7b36..cf915affa 100644
--- a/postgis/lwgeom_geos.c
+++ b/postgis/lwgeom_geos.c
@@ -1306,69 +1306,19 @@ PG_FUNCTION_INFO_V1(centroid);
 Datum centroid(PG_FUNCTION_ARGS)
 {
 	GSERIALIZED *geom, *result;
-	GEOSGeometry *geosgeom, *geosresult;
-	LWGEOM *igeom = NULL, *linear_geom = NULL;
-	int32 perQuad= 16;
-	int type = 0;
-	geom = PG_GETARG_GSERIALIZED_P(0);
-
-	/* Empty.Centroid() == Point Empty */
-	if ( gserialized_is_empty(geom) )
-	{
-		LWPOINT *lwp = lwpoint_construct_empty(
-		                   gserialized_get_srid(geom),
-		                   gserialized_has_z(geom),
-		                   gserialized_has_m(geom));
-		result = geometry_serialize(lwpoint_as_lwgeom(lwp));
-		lwpoint_free(lwp);
-		PG_RETURN_POINTER(result);
-	}
-
-	type = gserialized_get_type(geom) ;
-	/* Converting curve geometry to linestring if necessary*/
-	if(type == CIRCSTRINGTYPE || type == COMPOUNDTYPE )
-	{/* curve geometry?*/
-		igeom = lwgeom_from_gserialized(geom);
-		PG_FREE_IF_COPY(geom, 0); /*free memory, we already have a lwgeom geometry copy*/
-		linear_geom = lwgeom_stroke(igeom, perQuad);
-		lwgeom_free(igeom);
-		if (!linear_geom) PG_RETURN_NULL();
-
-		geom = geometry_serialize(linear_geom);
-		lwgeom_free(linear_geom);
-	}
-
-	initGEOS(lwpgnotice, lwgeom_geos_error);
-
-	geosgeom = POSTGIS2GEOS(geom);
+	LWGEOM *lwgeom, *lwresult;
 
-	if (!geosgeom)
-		HANDLE_GEOS_ERROR("First argument geometry could not be converted to GEOS");
-
-	geosresult = GEOSGetCentroid(geosgeom);
-
-	if (!geosresult)
-	{
-		GEOSGeom_destroy(geosgeom);
-		HANDLE_GEOS_ERROR("GEOSGetCentroid");
-	}
-
-	GEOSSetSRID(geosresult, gserialized_get_srid(geom));
-
-	result = GEOS2POSTGIS(geosresult, gserialized_has_z(geom));
-
-	if (!result)
-	{
-		GEOSGeom_destroy(geosgeom);
-		GEOSGeom_destroy(geosresult);
-		elog(ERROR,"Error in GEOS-PGIS conversion");
-		PG_RETURN_NULL();
-	}
-	GEOSGeom_destroy(geosgeom);
-	GEOSGeom_destroy(geosresult);
+	geom = PG_GETARG_GSERIALIZED_P(0);
 
+	lwgeom = lwgeom_from_gserialized(geom);
+	lwresult = lwgeom_centroid(lwgeom);
+	lwgeom_free(lwgeom);
 	PG_FREE_IF_COPY(geom, 0);
 
+	if (!lwresult) PG_RETURN_NULL();
+
+	result = geometry_serialize(lwresult);
+	lwgeom_free(lwresult);
 	PG_RETURN_POINTER(result);
 }
 
diff --git a/postgis/postgis.sql.in b/postgis/postgis.sql.in
index b99cefde8..6e878bd02 100644
--- a/postgis/postgis.sql.in
+++ b/postgis/postgis.sql.in
@@ -3710,7 +3710,6 @@ CREATE OR REPLACE FUNCTION ST_Node(g geometry)
 --
 --
 -- Availability: 2.1.0
--- Requires GEOS >= 3.4.0
 --
 CREATE OR REPLACE FUNCTION ST_DelaunayTriangles(g1 geometry, tolerance float8 DEFAULT 0.0, flags int4 DEFAULT 0)
        RETURNS geometry
-- 
2.40.0