Merge ways and relations fetch from table osm_building_polygon (#757)

Build on top of PR #755, to be merged first.

Since we want every thing from osm_building_polygon (osm_id >= 0 and osm_id < 0), we can merge the two queries.

Note: the obp.osm_id >= 0 on the left join only apply to the left join part.

layers/building/building.sql

@@ -46,22 +46,6 @@ CREATE OR REPLACE VIEW osm_all_buildings AS (
          osm_building_associatedstreet WHERE role = 'house' AND ST_GeometryType(geometry) = 'ST_Polygon'
          UNION ALL
 
-         -- etldoc: osm_building_polygon -> layer_building:z14_
-         -- Buildings that are from multipolygons
-         SELECT osm_id,geometry,
-                  COALESCE(nullif(as_numeric(height),-1),nullif(as_numeric(buildingheight),-1)) as height,
-                  COALESCE(nullif(as_numeric(min_height),-1),nullif(as_numeric(buildingmin_height),-1)) as min_height,
-                  COALESCE(nullif(as_numeric(levels),-1),nullif(as_numeric(buildinglevels),-1)) as levels,
-                  COALESCE(nullif(as_numeric(min_level),-1),nullif(as_numeric(buildingmin_level),-1)) as min_level,
-                  nullif(material, '') AS material,
-                  nullif(colour, '') AS colour,
-                  FALSE as hide_3d
-         FROM
-         osm_building_polygon obp
-         -- OSM mulipolygons once imported can give unique postgis polygons with holes, or multi parts polygons
-         WHERE osm_id < 0 AND ST_GeometryType(geometry) IN ('ST_Polygon', 'ST_MultiPolygon')
-
-         UNION ALL
          -- etldoc: osm_building_polygon -> layer_building:z14_
          -- Standalone buildings
          SELECT obp.osm_id,obp.geometry,
@@ -74,9 +58,11 @@ CREATE OR REPLACE VIEW osm_all_buildings AS (
                   obr.role IS NOT NULL AS hide_3d
          FROM
          osm_building_polygon obp
-           LEFT JOIN osm_building_relation obr ON obr.member = obp.osm_id AND obr.role = 'outline'
-         -- Only check for ST_Polygon as we exclude buildings from relations keeping only positive ids
-         WHERE obp.osm_id >= 0 AND ST_GeometryType(obp.geometry) = 'ST_Polygon'
+           LEFT JOIN osm_building_relation obr ON
+             obp.osm_id >= 0 AND
+             obr.member = obp.osm_id AND
+             obr.role = 'outline'
+         WHERE ST_GeometryType(obp.geometry) IN ('ST_Polygon', 'ST_MultiPolygon')
 );
 
 CREATE OR REPLACE FUNCTION layer_building(bbox geometry, zoom_level int)