From 4dff665e8b67a1eccec327993cf6ae736d02f33a Mon Sep 17 00:00:00 2001
From: Paul Ramsey <pramsey@cleverelephant.ca>
Date: Sun, 28 Feb 2016 23:46:41 +0000
Subject: [PATCH] #3479, error out if kmeans has k > ngeoms

git-svn-id: http://svn.osgeo.org/postgis/trunk@14719 b70326c6-7e19-0410-871a-916f4a2858ee
---
 liblwgeom/kmeans.c      | 1 +
 liblwgeom/lwkmeans.c    | 5 +++++
 postgis/lwgeom_window.c | 6 ++++++
 3 files changed, 12 insertions(+)

diff --git a/liblwgeom/kmeans.c b/liblwgeom/kmeans.c
index 8ec25112b..4d4c70eae 100644
--- a/liblwgeom/kmeans.c
+++ b/liblwgeom/kmeans.c
@@ -260,6 +260,7 @@ kmeans(kmeans_config *config)
 	assert(config->centers);
 	assert(config->k);
 	assert(config->clusters);
+	assert(config->k < config->num_objs);
 
 	/* Zero out cluster numbers, just in case user forgets */
 	memset(config->clusters, 0, clusters_sz);
diff --git a/liblwgeom/lwkmeans.c b/liblwgeom/lwkmeans.c
index 10a7d2ad5..70b7005bb 100644
--- a/liblwgeom/lwkmeans.c
+++ b/liblwgeom/lwkmeans.c
@@ -90,6 +90,11 @@ lwgeom_cluster_2d_kmeans(const LWGEOM **geoms, int ngeoms, int k)
 	assert(k>0);
 	assert(ngeoms>0);
 	assert(geoms);
+	
+	if (ngeoms<k)
+	{
+		lwerror("%s: number of geometries is less than the number of clusters requested", __func__);
+	}
 
 	/* We'll hold the temporary centroid objects here */
 	centroids = lwalloc(sizeof(LWGEOM*) * ngeoms);
diff --git a/postgis/lwgeom_window.c b/postgis/lwgeom_window.c
index afc3af074..779cd472d 100644
--- a/postgis/lwgeom_window.c
+++ b/postgis/lwgeom_window.c
@@ -196,6 +196,12 @@ Datum ST_ClusterKMeans(PG_FUNCTION_ARGS)
 			PG_RETURN_NULL();
 		}
 
+		/* Error out if N < K */
+		if (N<k)
+		{
+			lwpgerror("K (%d) must be smaller than the number of rows in the group (%d)", k, N);
+		}
+
 		/* Read all the geometries from the partition window into a list */
 		geoms = palloc(sizeof(LWGEOM*) * N);
 		for (i = 0; i < N; i++)
-- 
2.40.0