linked centroids must always be within geometry

When using a linked place as centroid for a boundary, check
first that it is really within the area. If it is outside,
just keep the computed centroid because a centroid outside the
area just causes havok.

Fixes #1352.

sql/functions/placex_triggers.sql

@@ -609,6 +609,8 @@ DECLARE
   location RECORD;
   relation_members TEXT[];
 
+  centroid GEOMETRY;
+
   addr_street TEXT;
   addr_place TEXT;
 
@@ -683,10 +685,10 @@ BEGIN
   -- Speed up searches - just use the centroid of the feature
   -- cheaper but less acurate
   NEW.centroid := ST_PointOnSurface(NEW.geometry);
-  -- For searching near features rather use the centroid
-  NEW.postcode := null;
   --DEBUG: RAISE WARNING 'Computing preliminary centroid at %',ST_AsText(NEW.centroid);
 
+  NEW.postcode := null;
+
   -- recalculate country and partition
   IF NEW.rank_search = 4 AND NEW.address is not NULL AND NEW.address ? 'country' THEN
     -- for countries, believe the mapped country code,
@@ -837,9 +839,12 @@ BEGIN
   IF location.place_id is not null THEN
     --DEBUG: RAISE WARNING 'Linked %', location;
 
-    -- Use this as the centre point of the geometry
-    NEW.centroid := coalesce(location.centroid,
-                             ST_Centroid(location.geometry));
+    -- Use the linked point as the centre point of the geometry,
+    -- but only if it is within the area of the boundary.
+    centroid := coalesce(location.centroid, ST_Centroid(location.geometry));
+    IF centroid is not NULL AND ST_Within(centroid, NEW.geometry) THEN
+        NEW.centroid := centroid;
+    END IF;
 
     -- Use the address rank of the linked place, if it has one
     IF location.rank_address between 5 and 25 THEN

test/bdd/db/import/linking.feature

@@ -198,3 +198,21 @@ Feature: Linking of places
           | ID | osm_type | osm_id |
           |  0 | N | 2 |
 
+    # github #1352
+    Scenario: Do not use linked centroid when it is outside the area
+        Given the named places
+         | osm  | class    | type           | admin | geometry |
+         | R13  | boundary | administrative | 4     | poly-area:0.01 |
+        And the named places
+         | osm  | class    | type           | geometry |
+         | N2   | place    | city           | 0.1 0.1 |
+        And the relations
+         | id | members       | tags+type |
+         | 13 | N2:label      | boundary |
+        When importing
+        Then placex contains
+         | object | linked_place_id |
+         | N2     | R13             |
+        And placex contains
+         | object | centroid |
+         | R13    | in geometry  |

test/bdd/steps/db_ops.py

@@ -197,10 +197,18 @@ def assert_db_column(row, column, value, context):
         return
 
     if column.startswith('centroid'):
-        fac = float(column[9:]) if column.startswith('centroid*') else 1.0
-        x, y = value.split(' ')
-        assert_almost_equal(float(x) * fac, row['cx'], "Bad x coordinate")
-        assert_almost_equal(float(y) * fac, row['cy'], "Bad y coordinate")
+        if value == 'in geometry':
+            query = """SELECT ST_Within(ST_SetSRID(ST_Point({}, {}), 4326),
+                                        ST_SetSRID('{}'::geometry, 4326))""".format(
+                      row['cx'], row['cy'], row['geomtxt'])
+            cur = context.db.cursor()
+            cur.execute(query)
+            eq_(cur.fetchone()[0], True, "(Row %s failed: %s)" % (column, query))
+        else:
+            fac = float(column[9:]) if column.startswith('centroid*') else 1.0
+            x, y = value.split(' ')
+            assert_almost_equal(float(x) * fac, row['cx'], msg="Bad x coordinate")
+            assert_almost_equal(float(y) * fac, row['cy'], msg="Bad y coordinate")
     elif column == 'geometry':
         geom = context.osm.parse_geometry(value, context.scene)
         cur = context.db.cursor()