Coalesce duplicate route concurrencies (#1361)

# Problem description
#1128 introduced route relation concurrency information in OpenMapTiles via the `route_X` attributes.  The original implementation assumed that there would be a single route relation for each `network` and `ref` pair.  However, it is increasingly common practice to tag a separate route relation for each direction of a route in order to provide awareness to routers and other data consumers of the directionality of a route.  This standard and growing practice is described on the [OSM wiki page on route directions](https://wiki.openstreetmap.org/wiki/Route_directions).  Thus, the naïve implementation of #1128 caused duplicate entries to be added as `route_X` attributes in the case where separate route relations were used for directional routes.

# Solution description
This PR adds grouping when computing route concurrency information, such that duplicate entries are coalesced in a predictable way.  Since this grouping is done only within a route membership join of a single member way, the computational complexity should be trivial.

layers/transportation/update_route_member.sql

@@ -149,6 +149,17 @@ CREATE INDEX IF NOT EXISTS osm_route_member_ref_idx ON osm_route_member ("ref");
 
 CREATE INDEX IF NOT EXISTS osm_route_member_network_type_idx ON osm_route_member ("network_type");
 
+/**
+* Discard duplicate routes
+*/
+DELETE FROM osm_route_member WHERE id IN
+   (SELECT id
+    FROM (SELECT id,
+                 ROW_NUMBER() OVER (partition BY member, network, ref ORDER BY id) AS rnum
+          FROM osm_route_member) t
+    WHERE t.rnum > 1);
+CREATE UNIQUE INDEX IF NOT EXISTS osm_route_member_network_ref_idx ON osm_route_member ("member", "network", "ref");
+
 CREATE INDEX IF NOT EXISTS osm_highway_linestring_osm_id_idx ON osm_highway_linestring ("osm_id");
 CREATE UNIQUE INDEX IF NOT EXISTS osm_highway_linestring_gen_z11_osm_id_idx ON osm_highway_linestring_gen_z11 ("osm_id");
 

tests/import/500_import-highway.osm

@@ -147,4 +147,22 @@
     <tag k="route" v="hiking"/>
     <tag k="network" v="nwn"/>
   </relation>
+
+  <!-- Route Concurrency de-duplication -->
+  <relation id="515" visible="true" timestamp="2019-01-01T00:00:00Z" version="1" changeset="1" user="u" uid="1">
+    <member type="way" ref="5000" role=""/>
+    <tag k="type" v="route"/>
+    <tag k="route" v="road"/>
+    <tag k="network" v="US:I"/>
+    <tag k="ref" v="95"/>
+    <tag k="description" v="I-95 Northbound"/>
+  </relation>
+  <relation id="516" visible="true" timestamp="2019-01-01T00:00:00Z" version="1" changeset="1" user="u" uid="1">
+    <member type="way" ref="5000" role=""/>
+    <tag k="type" v="route"/>
+    <tag k="route" v="road"/>
+    <tag k="network" v="US:I"/>
+    <tag k="ref" v="95"/>
+    <tag k="description" v="I-95 Southbound"/>
+  </relation>
 </osm>

tests/test-post-import.sql

@@ -160,6 +160,13 @@ BEGIN
     INSERT INTO omt_test_failures VALUES(500, 'import', 'osm_transportation_name_linestring z12 route_rank expected 1, got ' || cnt);
   END IF;
 
+  -- Duplicate route concurrencies collapsed
+  SELECT COUNT(*) INTO cnt FROM osm_route_member
+    WHERE network='US:I' AND ref='95';
+  IF cnt <> 1 THEN
+    INSERT INTO omt_test_failures VALUES(500, 'import', 'osm_route_member 1 route membership expected, got ' || cnt);
+  END IF;
+
   -- Test 600
 
   -- verify that atms are imported with correct name which can come from tags like operator or network