Precompute generalisation for roads and remove CTEs

schema/layers/road.sql

@@ -7,7 +7,7 @@ CREATE OR REPLACE FUNCTION ne_road_class(type VARCHAR) RETURNS VARCHAR AS $$
   END;
 $$ LANGUAGE SQL IMMUTABLE;
 
-CREATE OR REPLACE VIEW ne_10m_global_roads AS (
+CREATE TABLE IF NOT EXISTS ne_10m_global_roads AS (
     SELECT geom, scalerank, ne_road_class(type) AS class
     FROM ne_10m_roads
     WHERE continent <> 'North America'
@@ -19,6 +19,9 @@ CREATE OR REPLACE VIEW ne_10m_global_roads AS (
     WHERE type IN ('Major Highway', 'Secondary Highway', 'Road')
 );
 
+CREATE INDEX IF NOT EXISTS ne_10m_global_roads_geom_idx ON ne_10m_global_roads USING gist(geom);
+CREATE INDEX IF NOT EXISTS ne_10m_global_roads_scalerank_idx ON ne_10m_global_roads(scalerank);
+
 CREATE OR REPLACE VIEW road_z4 AS (
     SELECT geom, class
     FROM ne_10m_global_roads
@@ -43,29 +46,33 @@ CREATE OR REPLACE VIEW road_z7 AS (
     WHERE scalerank <= 7
 );
 
-CREATE OR REPLACE VIEW road_z8 AS (
-    SELECT way AS geom, class::text
+CREATE TABLE IF NOT EXISTS road_z8 AS (
+    SELECT ST_Simplify(way, 200) AS geom, class::text
     FROM roads
     WHERE class IN ('motorway','trunk')
 );
+CREATE INDEX IF NOT EXISTS road_z8_geom_idx ON road_z8 USING gist(geom);
 
-CREATE OR REPLACE VIEW road_z9 AS (
-    SELECT way AS geom, class::text
+CREATE TABLE IF NOT EXISTS road_z9 AS (
+    SELECT ST_Simplify(way, 120) AS geom, class::text
     FROM roads
     WHERE class IN ('motorway','trunk', 'primary')
 );
+CREATE INDEX IF NOT EXISTS road_z9_geom_idx ON road_z9 USING gist(geom);
 
-CREATE OR REPLACE VIEW road_z10 AS (
-    SELECT way AS geom, class::text
+CREATE TABLE IF NOT EXISTS road_z10 AS (
+    SELECT ST_Simplify(way, 50) AS geom, class::text
     FROM roads
     WHERE class IN ('motorway','trunk', 'primary', 'secondary')
 );
+CREATE INDEX IF NOT EXISTS road_z10_geom_idx ON road_z10 USING gist(geom);
 
-CREATE OR REPLACE VIEW road_z11 AS (
-    SELECT way AS geom, class::text
+CREATE TABLE IF NOT EXISTS road_z11 AS (
+    SELECT ST_Simplify(way, 20) AS geom, class::text
     FROM roads
     WHERE class IN ('motorway','trunk', 'primary', 'secondary', 'tertiary')
 );
+CREATE INDEX IF NOT EXISTS road_z11_geom_idx ON road_z11 USING gist(geom);
 
 CREATE OR REPLACE VIEW road_z12 AS (
     SELECT way AS geom, class::text
@@ -95,7 +102,7 @@ CREATE OR REPLACE VIEW road_z14 AS (
 
 CREATE OR REPLACE FUNCTION layer_road(bbox geometry, zoom_level int)
 RETURNS TABLE(geom geometry, class text) AS $$
-    WITH zoom_levels AS (
+    SELECT geom, class::text FROM (
         SELECT * FROM road_z4 WHERE zoom_level BETWEEN 4 AND 5
         UNION ALL
         SELECT * FROM road_z5 WHERE zoom_level = 5
@@ -106,18 +113,17 @@ RETURNS TABLE(geom geometry, class text) AS $$
         UNION ALL
         SELECT * FROM road_z8 WHERE zoom_level = 8
         UNION ALL
-        SELECT ST_Simplify(geom, 200), class FROM road_z9 WHERE zoom_level = 9
+        SELECT geom, class FROM road_z9 WHERE zoom_level = 9
         UNION ALL
-        SELECT ST_Simplify(geom, 120), class FROM road_z10 WHERE zoom_level = 10
+        SELECT geom, class FROM road_z10 WHERE zoom_level = 10
         UNION ALL
-        SELECT ST_Simplify(geom, 50), class FROM road_z11 WHERE zoom_level = 11
+        SELECT geom, class FROM road_z11 WHERE zoom_level = 11
         UNION ALL
-        SELECT ST_Simplify(geom, 20), class FROM road_z12 WHERE zoom_level = 12
+        SELECT geom, class FROM road_z12 WHERE zoom_level = 12
         UNION ALL
         SELECT * FROM road_z13 WHERE zoom_level = 13
         UNION ALL
         SELECT * FROM road_z14 WHERE zoom_level >= 14
-    )
-    SELECT geom, class::text FROM zoom_levels
+    ) AS t
     WHERE geom && bbox;
 $$ LANGUAGE SQL IMMUTABLE;