fix incorrect segment iteration in prepared geometry ops

src/sgl/sgl.cpp

@@ -2369,7 +2369,9 @@ point_in_polygon_result prepared_geometry::contains(const vertex_xy &vert) const
 
 			// Now, we are at a leaf, so we need to check the segments
 			const auto beg_idx = entry * NODE_SIZE;
-			const auto end_idx = math::min(beg_idx + NODE_SIZE, index.items_count);
+			// We +1 to the node size here to get the end index, because the last segment spans across
+			// the end of the node. And our indexes are always sequential.
+			const auto end_idx = math::min(beg_idx + NODE_SIZE + 1, index.items_count);
 
 			// Loop over the segments
 			vertex_xy prev;
@@ -2436,7 +2438,9 @@ bool prepared_geometry::try_get_distance_recursive(uint32_t level, uint32_t entr
 		const auto vertex_width = get_vertex_width();
 
 		const auto beg_idx = entry * NODE_SIZE;
-		const auto end_idx = math::min(beg_idx + NODE_SIZE, index.items_count);
+		// We +1 to the node size here to get the end index, because the last segment spans across
+		// the end of the node. And our indexes are always sequential.
+		const auto end_idx = math::min(beg_idx + NODE_SIZE + 1, index.items_count);
 
 		if (beg_idx >= end_idx) {
 			return false; // No segments to check

test/sql/geometry/st_distance.test

@@ -0,0 +1,25 @@
+require spatial
+
+# This test case comes from a bug report, where the indexed point-in-polygon check would not consider that
+# the second vertex of the last segment in each index node neccessarily have to be the first vertex of the next segment.
+# Therefore when performing a raycast from a point to a polygon where the ray would intersect
+# the segment formed by the last vertex in a index leaf node, and the first vertex in the next segment, the result
+# would be incorrect.
+# To test this, we create a polygon with 40 vertices, causing two index leaf nodes (0-31, 33-40) to be created when
+# preparing the polygon, and we then query a point that is to the left of the polygon, but right between the segment
+# spanning the two nodes (31-32).
+
+query I
+SELECT ST_Distance(
+     ST_Point(-5, 31),
+     -- 32 points
+     ST_GeomFromText('POLYGON((
+         0  0, 0  1, 0  2, 0  3, 0  4, 0  5, 0  6, 0  7,
+         0  8, 0  9, 0 10, 0 11, 0 12, 0 13, 0 14, 0 15,
+         0 16, 0 17, 0 18, 0 19, 0 20, 0 21, 0 22, 0 23,
+         0 24, 0 25, 0 26, 0 27, 0 28, 0 29, 0 30, 0 31,
+         0 32, 0 33, 0 34, 0 35, 0 36, 0 37, 0 38, 0 39,
+         0 0))'));
+----
+5
+