More nuanced waterway

layers/waterway/merge_waterway.sql

@@ -0,0 +1,44 @@
+-- We merge the waterways by name like the highways
+-- This helps to drop not important rivers (since they do not have a name)
+-- and also makes it possible to filter out too short rivers
+
+-- etldoc: osm_waterway_linestring ->  osm_important_waterway_linestring
+CREATE TABLE IF NOT EXISTS osm_important_waterway_linestring AS (
+    SELECT
+        (ST_Dump(geometry)).geom AS geometry,
+        name
+    FROM (
+        SELECT
+            ST_LineMerge(ST_Union(geometry)) AS geometry,
+            name
+        FROM osm_waterway_linestring
+        WHERE name <> '' AND waterway = 'river'
+        GROUP BY name
+    ) AS waterway_union
+);
+
+CREATE INDEX IF NOT EXISTS osm_important_waterway_linestring_geometry_idx ON osm_important_waterway_linestring USING gist(geometry);
+
+-- etldoc: osm_important_waterway_linestring -> osm_important_waterway_linestring_gen1
+CREATE TABLE IF NOT EXISTS osm_important_waterway_linestring_gen1 AS (
+    SELECT ST_Simplify(geometry, 60) AS geometry, name
+    FROM osm_important_waterway_linestring
+    WHERE ST_Length(geometry) > 1000
+);
+CREATE INDEX IF NOT EXISTS osm_important_waterway_linestring_gen1_geometry_idx ON osm_important_waterway_linestring_gen1 USING gist(geometry);
+
+-- etldoc: osm_important_waterway_linestring_gen1 -> osm_important_waterway_linestring_gen2
+CREATE TABLE IF NOT EXISTS osm_important_waterway_linestring_gen2 AS (
+    SELECT ST_Simplify(geometry, 100) AS geometry, name
+    FROM osm_important_waterway_linestring_gen1
+    WHERE ST_Length(geometry) > 4000
+);
+CREATE INDEX IF NOT EXISTS osm_important_waterway_linestring_gen2_geometry_idx ON osm_important_waterway_linestring_gen2 USING gist(geometry);
+
+-- etldoc: osm_important_waterway_linestring_gen2 -> osm_important_waterway_linestring_gen3
+CREATE TABLE IF NOT EXISTS osm_important_waterway_linestring_gen3 AS (
+    SELECT ST_Simplify(geometry, 200) AS geometry, name
+    FROM osm_important_waterway_linestring_gen2
+    WHERE ST_Length(geometry) > 8000
+);
+CREATE INDEX IF NOT EXISTS osm_important_waterway_linestring_gen3_geometry_idx ON osm_important_waterway_linestring_gen3 USING gist(geometry);