Refactor water into table function

data.yml

@@ -23,51 +23,8 @@ Layer:
       max_size: 512
       password: osm
       port: 5432
-      srid: ''
-      table: |-
-        ( SELECT *
-          FROM (
-              SELECT * FROM water_z0
-              WHERE z(!scale_denominator!) = 0
-              UNION ALL
-              SELECT * FROM water_z1
-              WHERE z(!scale_denominator!) = 1
-              UNION ALL
-              SELECT * FROM water_z2
-              WHERE z(!scale_denominator!) = 2
-              UNION ALL
-              SELECT * FROM water_z3
-              WHERE z(!scale_denominator!) = 3
-              UNION ALL
-              SELECT * FROM water_z4
-              WHERE z(!scale_denominator!) = 4
-              UNION ALL
-              SELECT * FROM water_z5
-              WHERE z(!scale_denominator!) = 5
-              UNION ALL
-              SELECT * FROM water_z6
-              WHERE z(!scale_denominator!) = 6
-              UNION ALL
-              SELECT ST_SimplifyPreserveTopology(geom, 200) AS geom FROM water_z8
-              WHERE z(!scale_denominator!) = 8
-              UNION ALL
-              SELECT ST_SimplifyPreserveTopology(geom, 100) AS geom FROM water_z8
-              WHERE z(!scale_denominator!) BETWEEN 9 AND 10
-              UNION ALL
-              SELECT * FROM water_z11
-              WHERE z(!scale_denominator!) = 11
-              UNION ALL
-              SELECT * FROM water_z12
-              WHERE z(!scale_denominator!) = 12
-              UNION ALL
-              SELECT * FROM water_z13
-              WHERE z(!scale_denominator!) = 13
-              UNION ALL
-              SELECT * FROM water_z14
-              WHERE z(!scale_denominator!) >= 14
-          ) AS water
-          WHERE geom && !bbox!
-        ) AS data
+      srid: 900913
+      table: (SELECT * FROM layer_water(!bbox!, z(!scale_denominator!))) AS t
       type: postgis
       user: osm
     description: Ocean and lake polygons

schema/layers/water.sql

@@ -55,45 +55,91 @@ CREATE OR REPLACE VIEW water_z6 AS (
 CREATE OR REPLACE VIEW water_z8 AS (
     SELECT way AS geom FROM water_areas
     WHERE way_area > 1000000
-	UNION ALL
-	SELECT way AS geom FROM waterways
-	WHERE waterway IN ('river') AND ST_Length(way) > 10000
+    UNION ALL
+    SELECT way AS geom FROM waterways
+    WHERE waterway IN ('river') AND ST_Length(way) > 10000
 );
 
 CREATE OR REPLACE VIEW water_z9 AS (
     SELECT way AS geom FROM water_areas
     WHERE way_area > 500000
-	UNION ALL
-	SELECT way AS geom FROM waterways
-	WHERE waterway IN ('river') AND ST_Length(way) > 5000
+    UNION ALL
+    SELECT way AS geom FROM waterways
+    WHERE waterway IN ('river') AND ST_Length(way) > 5000
 );
 
 CREATE OR REPLACE VIEW water_z11 AS (
     SELECT way AS geom FROM water_areas
     WHERE way_area > 50000
-	UNION ALL
-	SELECT way AS geom FROM waterways
-	WHERE waterway IN ('river')
+    UNION ALL
+    SELECT way AS geom FROM waterways
+    WHERE waterway IN ('river')
 );
 
 CREATE OR REPLACE VIEW water_z12 AS (
     SELECT way AS geom FROM water_areas
     WHERE way_area > 40000
-	UNION ALL
-	SELECT way AS geom FROM waterways
-	WHERE waterway IN ('river', 'canal', 'stream')
+    UNION ALL
+    SELECT way AS geom FROM waterways
+    WHERE waterway IN ('river', 'canal', 'stream')
 );
 
 CREATE OR REPLACE VIEW water_z13 AS (
     SELECT way AS geom FROM water_areas
     WHERE way_area > 2000
-	UNION ALL
-	SELECT way AS geom FROM waterways
-	WHERE waterway IN ('river', 'canal', 'stream', 'drain', 'ditch')
+    UNION ALL
+    SELECT way AS geom FROM waterways
+    WHERE waterway IN ('river', 'canal', 'stream', 'drain', 'ditch')
 );
 
 CREATE OR REPLACE VIEW water_z14 AS (
     SELECT way AS geom FROM water_areas
-	UNION ALL
-	SELECT way AS geom FROM waterways
+    UNION ALL
+    SELECT way AS geom FROM waterways
 );
+
+CREATE OR REPLACE FUNCTION layer_water (bbox geometry, zoom_level int)
+RETURNS TABLE(geom geometry) AS $$
+    WITH zoom_levels AS (
+        SELECT * FROM water_z0
+        WHERE zoom_level = 0
+        UNION ALL
+        SELECT * FROM water_z1
+        WHERE zoom_level = 1
+        UNION ALL
+        SELECT * FROM water_z2
+        WHERE zoom_level = 2
+        UNION ALL
+        SELECT * FROM water_z3
+        WHERE zoom_level = 3
+        UNION ALL
+        SELECT * FROM water_z4
+        WHERE zoom_level = 4
+        UNION ALL
+        SELECT * FROM water_z5
+        WHERE zoom_level = 5
+        UNION ALL
+        SELECT * FROM water_z6
+        WHERE zoom_level = 6
+        UNION ALL
+        SELECT ST_SimplifyPreserveTopology(geom, 200) AS geom FROM water_z8
+        WHERE zoom_level = 8
+        UNION ALL
+        SELECT ST_SimplifyPreserveTopology(geom, 100) AS geom FROM water_z8
+        WHERE zoom_level BETWEEN 9 AND 10
+        UNION ALL
+        SELECT * FROM water_z11
+        WHERE zoom_level = 11
+        UNION ALL
+        SELECT * FROM water_z12
+        WHERE zoom_level = 12
+        UNION ALL
+        SELECT * FROM water_z13
+        WHERE zoom_level = 13
+        UNION ALL
+        SELECT * FROM water_z14
+        WHERE zoom_level >= 14
+    )
+    SELECT geom FROM zoom_levels
+    WHERE geom && bbox;
+$$ LANGUAGE SQL;