add state name to national borders (#1039)

This PR adds state name to national borders (`admin_level=2`)

From zoom level 3 there is an added `adm0_l` and `adm0_r` attribute for national borders.

There is 3 main steps: 
1) union border lines from OSM and keep separate LineString between intersects
2) create polygons from step 1), create a point in each state polygon, add to this point a state abbreviation from NaturalEarth Data
3) create a short parallel line on the left and right of a small part of the border in 70m distance, and add information about which state overlap this short line.

layers/boundary/boundary.sql

@@ -9,12 +9,16 @@ $$
 $$ LANGUAGE plpgsql;
 
 -- etldoc: osm_border_linestring -> osm_border_linestring_gen1
+-- etldoc: osm_border_linestring_adm -> osm_border_linestring_gen1
 DROP MATERIALIZED VIEW IF EXISTS osm_border_linestring_gen1 CASCADE;
 CREATE MATERIALIZED VIEW osm_border_linestring_gen1 AS
 (
-SELECT ST_Simplify(geometry, 10) AS geometry, osm_id, admin_level, dividing_line, disputed, maritime
+SELECT ST_Simplify(geometry, 10) AS geometry, NULL AS adm0_l, NULL AS adm0_r, admin_level, disputed, maritime
 FROM osm_border_linestring
-WHERE admin_level <= 10
+WHERE admin_level BETWEEN 3 AND 10
+UNION ALL
+SELECT ST_Simplify(geometry, 10) AS geometry, adm0_l, adm0_r, admin_level, disputed, maritime
+FROM osm_border_linestring_adm
     ) /* DELAY_MATERIALIZED_VIEW_CREATION */ ;
 CREATE INDEX IF NOT EXISTS osm_border_linestring_gen1_idx ON osm_border_linestring_gen1 USING gist (geometry);
 
@@ -29,12 +33,16 @@ $$
 $$ LANGUAGE plpgsql;
 
 -- etldoc: osm_border_linestring -> osm_border_linestring_gen2
+-- etldoc: osm_border_linestring_adm -> osm_border_linestring_gen2
 DROP MATERIALIZED VIEW IF EXISTS osm_border_linestring_gen2 CASCADE;
 CREATE MATERIALIZED VIEW osm_border_linestring_gen2 AS
 (
-SELECT ST_Simplify(geometry, 20) AS geometry, osm_id, admin_level, dividing_line, disputed, maritime
+SELECT ST_Simplify(geometry, 20) AS geometry, NULL AS adm0_l, NULL AS adm0_r, admin_level, disputed, maritime
 FROM osm_border_linestring
-WHERE admin_level <= 10
+WHERE admin_level BETWEEN 3 AND 10
+UNION ALL
+SELECT ST_Simplify(geometry, 20) AS geometry, adm0_l, adm0_r, admin_level, disputed, maritime
+FROM osm_border_linestring_adm
     ) /* DELAY_MATERIALIZED_VIEW_CREATION */ ;
 CREATE INDEX IF NOT EXISTS osm_border_linestring_gen2_idx ON osm_border_linestring_gen2 USING gist (geometry);
 
@@ -49,12 +57,16 @@ $$
 $$ LANGUAGE plpgsql;
 
 -- etldoc: osm_border_linestring -> osm_border_linestring_gen3
+-- etldoc: osm_border_linestring_adm -> osm_border_linestring_gen3
 DROP MATERIALIZED VIEW IF EXISTS osm_border_linestring_gen3 CASCADE;
 CREATE MATERIALIZED VIEW osm_border_linestring_gen3 AS
 (
-SELECT ST_Simplify(geometry, 40) AS geometry, osm_id, admin_level, dividing_line, disputed, maritime
+SELECT ST_Simplify(geometry, 40) AS geometry, NULL AS adm0_l, NULL AS adm0_r, admin_level, disputed, maritime
 FROM osm_border_linestring
-WHERE admin_level <= 8
+WHERE admin_level BETWEEN 3 AND 8
+UNION ALL
+SELECT ST_Simplify(geometry, 40) AS geometry, adm0_l, adm0_r, admin_level, disputed, maritime
+FROM osm_border_linestring_adm
     ) /* DELAY_MATERIALIZED_VIEW_CREATION */ ;
 CREATE INDEX IF NOT EXISTS osm_border_linestring_gen3_idx ON osm_border_linestring_gen3 USING gist (geometry);
 
@@ -69,12 +81,16 @@ $$
 $$ LANGUAGE plpgsql;
 
 -- etldoc: osm_border_linestring -> osm_border_linestring_gen4
+-- etldoc: osm_border_linestring_adm -> osm_border_linestring_gen4
 DROP MATERIALIZED VIEW IF EXISTS osm_border_linestring_gen4 CASCADE;
 CREATE MATERIALIZED VIEW osm_border_linestring_gen4 AS
 (
-SELECT ST_Simplify(geometry, 80) AS geometry, osm_id, admin_level, dividing_line, disputed, maritime
+SELECT ST_Simplify(geometry, 80) AS geometry, NULL AS adm0_l, NULL AS adm0_r, admin_level, disputed, maritime
 FROM osm_border_linestring
-WHERE admin_level <= 6
+WHERE admin_level BETWEEN 3 AND 6
+UNION ALL
+SELECT ST_Simplify(geometry, 80) AS geometry, adm0_l, adm0_r, admin_level, disputed, maritime
+FROM osm_border_linestring_adm
     ) /* DELAY_MATERIALIZED_VIEW_CREATION */ ;
 CREATE INDEX IF NOT EXISTS osm_border_linestring_gen4_idx ON osm_border_linestring_gen4 USING gist (geometry);
 
@@ -89,12 +105,16 @@ $$
 $$ LANGUAGE plpgsql;
 
 -- etldoc: osm_border_linestring -> osm_border_linestring_gen5
+-- etldoc: osm_border_linestring_adm -> osm_border_linestring_gen5
 DROP MATERIALIZED VIEW IF EXISTS osm_border_linestring_gen5 CASCADE;
 CREATE MATERIALIZED VIEW osm_border_linestring_gen5 AS
 (
-SELECT ST_Simplify(geometry, 160) AS geometry, osm_id, admin_level, dividing_line, disputed, maritime
+SELECT ST_Simplify(geometry, 160) AS geometry, NULL AS adm0_l, NULL AS adm0_r, admin_level, disputed, maritime
 FROM osm_border_linestring
-WHERE admin_level <= 6
+WHERE admin_level BETWEEN 3 AND 6
+UNION ALL
+SELECT ST_Simplify(geometry, 160) AS geometry, adm0_l, adm0_r, admin_level, disputed, maritime
+FROM osm_border_linestring_adm
     ) /* DELAY_MATERIALIZED_VIEW_CREATION */ ;
 CREATE INDEX IF NOT EXISTS osm_border_linestring_gen5_idx ON osm_border_linestring_gen5 USING gist (geometry);
 
@@ -109,12 +129,16 @@ $$
 $$ LANGUAGE plpgsql;
 
 -- etldoc: osm_border_linestring -> osm_border_linestring_gen6
+-- etldoc: osm_border_linestring_adm -> osm_border_linestring_gen6
 DROP MATERIALIZED VIEW IF EXISTS osm_border_linestring_gen6 CASCADE;
 CREATE MATERIALIZED VIEW osm_border_linestring_gen6 AS
 (
-SELECT ST_Simplify(geometry, 300) AS geometry, osm_id, admin_level, dividing_line, disputed, maritime
+SELECT ST_Simplify(geometry, 300) AS geometry, NULL AS adm0_l, NULL AS adm0_r, admin_level, disputed, maritime
 FROM osm_border_linestring
-WHERE admin_level <= 4
+WHERE admin_level BETWEEN 3 AND 4
+UNION ALL
+SELECT ST_Simplify(geometry, 300) AS geometry, adm0_l, adm0_r, admin_level, disputed, maritime
+FROM osm_border_linestring_adm
     ) /* DELAY_MATERIALIZED_VIEW_CREATION */ ;
 CREATE INDEX IF NOT EXISTS osm_border_linestring_gen6_idx ON osm_border_linestring_gen6 USING gist (geometry);
 
@@ -129,12 +153,16 @@ $$
 $$ LANGUAGE plpgsql;
 
 -- etldoc: osm_border_linestring -> osm_border_linestring_gen7
+-- etldoc: osm_border_linestring_adm -> osm_border_linestring_gen7
 DROP MATERIALIZED VIEW IF EXISTS osm_border_linestring_gen7 CASCADE;
 CREATE MATERIALIZED VIEW osm_border_linestring_gen7 AS
 (
-SELECT ST_Simplify(geometry, 600) AS geometry, osm_id, admin_level, dividing_line, disputed, maritime
+SELECT ST_Simplify(geometry, 600) AS geometry, NULL AS adm0_l, NULL AS adm0_r, admin_level, disputed, maritime
 FROM osm_border_linestring
-WHERE admin_level <= 4
+WHERE admin_level BETWEEN 3 AND 4
+UNION ALL
+SELECT ST_Simplify(geometry, 600) AS geometry, adm0_l, adm0_r, admin_level, disputed, maritime
+FROM osm_border_linestring_adm
     ) /* DELAY_MATERIALIZED_VIEW_CREATION */ ;
 CREATE INDEX IF NOT EXISTS osm_border_linestring_gen7_idx ON osm_border_linestring_gen7 USING gist (geometry);
 
@@ -149,12 +177,16 @@ $$
 $$ LANGUAGE plpgsql;
 
 -- etldoc: osm_border_linestring -> osm_border_linestring_gen8
+-- etldoc: osm_border_linestring_adm -> osm_border_linestring_gen8
 DROP MATERIALIZED VIEW IF EXISTS osm_border_linestring_gen8 CASCADE;
 CREATE MATERIALIZED VIEW osm_border_linestring_gen8 AS
 (
-SELECT ST_Simplify(geometry, 1200) AS geometry, osm_id, admin_level, dividing_line, disputed, maritime
+SELECT ST_Simplify(geometry, 1200) AS geometry, NULL AS adm0_l, NULL AS adm0_r, admin_level, disputed, maritime
 FROM osm_border_linestring
-WHERE admin_level <= 4
+WHERE admin_level BETWEEN 3 AND 4
+UNION ALL
+SELECT ST_Simplify(geometry, 1200) AS geometry, adm0_l, adm0_r, admin_level, disputed, maritime
+FROM osm_border_linestring_adm
     ) /* DELAY_MATERIALIZED_VIEW_CREATION */ ;
 CREATE INDEX IF NOT EXISTS osm_border_linestring_gen8_idx ON osm_border_linestring_gen8 USING gist (geometry);
 
@@ -169,12 +201,16 @@ $$
 $$ LANGUAGE plpgsql;
 
 -- etldoc: osm_border_linestring -> osm_border_linestring_gen9
+-- etldoc: osm_border_linestring_adm -> osm_border_linestring_gen9
 DROP MATERIALIZED VIEW IF EXISTS osm_border_linestring_gen9 CASCADE;
 CREATE MATERIALIZED VIEW osm_border_linestring_gen9 AS
 (
-SELECT ST_Simplify(geometry, 2400) AS geometry, osm_id, admin_level, dividing_line, disputed, maritime
+SELECT ST_Simplify(geometry, 2400) AS geometry, NULL AS adm0_l, NULL AS adm0_r, admin_level, disputed, maritime
 FROM osm_border_linestring
-WHERE admin_level <= 4
+WHERE admin_level BETWEEN 3 AND 4
+UNION ALL
+SELECT ST_Simplify(geometry, 2400) AS geometry, adm0_l, adm0_r, admin_level, disputed, maritime
+FROM osm_border_linestring_adm
     ) /* DELAY_MATERIALIZED_VIEW_CREATION */ ;
 CREATE INDEX IF NOT EXISTS osm_border_linestring_gen9_idx ON osm_border_linestring_gen9 USING gist (geometry);
 
@@ -188,13 +224,12 @@ $$
     END;
 $$ LANGUAGE plpgsql;
 
--- etldoc: osm_border_linestring -> osm_border_linestring_gen10
+-- etldoc: osm_border_linestring_adm -> osm_border_linestring_gen10
 DROP MATERIALIZED VIEW IF EXISTS osm_border_linestring_gen10 CASCADE;
 CREATE MATERIALIZED VIEW osm_border_linestring_gen10 AS
 (
-SELECT ST_Simplify(geometry, 4800) AS geometry, osm_id, admin_level, dividing_line, disputed, maritime
+SELECT ST_Simplify(geometry, 4800) AS geometry, adm0_l, adm0_r, admin_level, disputed, maritime
-FROM osm_border_linestring
+FROM osm_border_linestring_adm
-WHERE admin_level <= 2
     ) /* DELAY_MATERIALIZED_VIEW_CREATION */ ;
 CREATE INDEX IF NOT EXISTS osm_border_linestring_gen10_idx ON osm_border_linestring_gen10 USING gist (geometry);
 
@@ -217,6 +252,8 @@ CREATE OR REPLACE VIEW boundary_z0 AS
 (
 SELECT geometry,
        2 AS admin_level,
+       NULL::text AS adm0_l,
+       NULL::text AS adm0_r,
        (CASE WHEN featurecla LIKE 'Disputed%' THEN TRUE ELSE FALSE END) AS disputed,
        (CASE WHEN featurecla LIKE 'Disputed%' THEN 'ne110m_' || ogc_fid ELSE NULL END) AS disputed_name,
        NULL::text AS claimed_by,
@@ -231,6 +268,8 @@ CREATE OR REPLACE VIEW boundary_z1 AS
 (
 SELECT geometry,
        2 AS admin_level,
+       NULL::text AS adm0_l,
+       NULL::text AS adm0_r,
        (CASE WHEN featurecla LIKE 'Disputed%' THEN TRUE ELSE FALSE END) AS disputed,
        (CASE WHEN featurecla LIKE 'Disputed%' THEN 'ne50m_' || ogc_fid ELSE NULL END) AS disputed_name,
        NULL AS claimed_by,
@@ -239,6 +278,8 @@ FROM ne_50m_admin_0_boundary_lines_land
 UNION ALL
 SELECT geometry,
        4 AS admin_level,
+       NULL::text AS adm0_l,
+       NULL::text AS adm0_r,
        FALSE AS disputed,
        NULL AS disputed_name,
        NULL AS claimed_by,
@@ -248,6 +289,8 @@ WHERE min_zoom <= 7
 UNION ALL
 SELECT geometry,
        admin_level,
+       NULL::text AS adm0_l,
+       NULL::text AS adm0_r,
        TRUE AS disputed,
        edit_name(name) AS disputed_name,
        claimed_by,
@@ -263,6 +306,8 @@ CREATE OR REPLACE VIEW boundary_z3 AS
 (
 SELECT geometry,
        2 AS admin_level,
+       NULL::text AS adm0_l,
+       NULL::text AS adm0_r,
        (CASE WHEN featurecla LIKE 'Disputed%' THEN TRUE ELSE FALSE END) AS disputed,
        (CASE WHEN featurecla LIKE 'Disputed%' THEN 'ne50m_' || ogc_fid ELSE NULL END) AS disputed_name,
        NULL AS claimed_by,
@@ -271,6 +316,8 @@ FROM ne_50m_admin_0_boundary_lines_land
 UNION ALL
 SELECT geometry,
        4 AS admin_level,
+       NULL::text AS adm0_l,
+       NULL::text AS adm0_r,
        FALSE AS disputed,
        NULL AS disputed_name,
        NULL AS claimed_by,
@@ -280,6 +327,8 @@ WHERE min_zoom <= 7
 UNION ALL
 SELECT geometry,
        admin_level,
+       NULL::text AS adm0_l,
+       NULL::text AS adm0_r,
        TRUE AS disputed,
        edit_name(name) AS disputed_name,
        claimed_by,
@@ -296,6 +345,8 @@ CREATE OR REPLACE VIEW boundary_z4 AS
 (
 SELECT geometry,
        2 AS admin_level,
+       adm0_a3_l AS adm0_l,
+       adm0_a3_r AS adm0_r,
        (CASE WHEN featurecla LIKE 'Disputed%' THEN TRUE ELSE FALSE END) AS disputed,
        (CASE WHEN featurecla LIKE 'Disputed%' THEN 'ne10m_' || ogc_fid ELSE NULL END) AS disputed_name,
        NULL AS claimed_by,
@@ -305,6 +356,8 @@ WHERE featurecla <> 'Lease limit'
 UNION ALL
 SELECT geometry,
        4 AS admin_level,
+       NULL::text AS adm0_l,
+       NULL::text AS adm0_r,
        FALSE AS disputed,
        NULL AS disputed_name,
        NULL AS claimed_by,
@@ -314,6 +367,8 @@ WHERE min_zoom <= 7
 UNION ALL
 SELECT geometry,
        admin_level,
+       adm0_l,
+       adm0_r,
        disputed,
        NULL AS disputed_name,
        NULL AS claimed_by,
@@ -324,6 +379,8 @@ WHERE maritime = TRUE
 UNION ALL
 SELECT geometry,
        admin_level,
+       NULL::text AS adm0_l,
+       NULL::text AS adm0_r,
        TRUE AS disputed,
        edit_name(name) AS disputed_name,
        claimed_by,
@@ -337,16 +394,21 @@ CREATE OR REPLACE VIEW boundary_z5 AS
 (
 SELECT geometry,
        admin_level,
+       adm0_l,
+       adm0_r,
        disputed,
        NULL AS disputed_name,
        NULL AS claimed_by,
        maritime
 FROM osm_border_linestring_gen9
 WHERE admin_level <= 4
-  AND osm_id NOT IN (SELECT DISTINCT osm_id FROM osm_border_disp_linestring_gen9)
+-- already not included in osm_border_linestring_adm
+-- AND osm_id NOT IN (SELECT DISTINCT osm_id FROM osm_border_disp_linestring_gen9)
 UNION ALL
 SELECT geometry,
        admin_level,
+       NULL::text AS adm0_l,
+       NULL::text AS adm0_r,
        TRUE AS disputed,
        edit_name(name) AS disputed_name,
        claimed_by,
@@ -360,16 +422,20 @@ CREATE OR REPLACE VIEW boundary_z6 AS
 (
 SELECT geometry,
        admin_level,
+       adm0_l,
+       adm0_r,
        disputed,
        NULL AS disputed_name,
        NULL AS claimed_by,
        maritime
 FROM osm_border_linestring_gen8
 WHERE admin_level <= 4
-  AND osm_id NOT IN (SELECT DISTINCT osm_id FROM osm_border_disp_linestring_gen8)
+-- AND osm_id NOT IN (SELECT DISTINCT osm_id FROM osm_border_disp_linestring_gen8)
 UNION ALL
 SELECT geometry,
        admin_level,
+       NULL::text AS adm0_l,
+       NULL::text AS adm0_r,
        TRUE AS disputed,
        edit_name(name) AS disputed_name,
        claimed_by,
@@ -383,16 +449,20 @@ CREATE OR REPLACE VIEW boundary_z7 AS
 (
 SELECT geometry,
        admin_level,
+       adm0_l,
+       adm0_r,
        disputed,
        NULL AS disputed_name,
        NULL AS claimed_by,
        maritime
 FROM osm_border_linestring_gen7
 WHERE admin_level <= 6
-  AND osm_id NOT IN (SELECT DISTINCT osm_id FROM osm_border_disp_linestring_gen7)
+-- AND osm_id NOT IN (SELECT DISTINCT osm_id FROM osm_border_disp_linestring_gen7)
 UNION ALL
 SELECT geometry,
        admin_level,
+       NULL::text AS adm0_l,
+       NULL::text AS adm0_r,
        TRUE AS disputed,
        edit_name(name) AS disputed_name,
        claimed_by,
@@ -406,16 +476,20 @@ CREATE OR REPLACE VIEW boundary_z8 AS
 (
 SELECT geometry,
        admin_level,
+       adm0_l,
+       adm0_r,
        disputed,
        NULL AS disputed_name,
        NULL AS claimed_by,
        maritime
 FROM osm_border_linestring_gen6
 WHERE admin_level <= 6
-  AND osm_id NOT IN (SELECT DISTINCT osm_id FROM osm_border_disp_linestring_gen6)
+-- AND osm_id NOT IN (SELECT DISTINCT osm_id FROM osm_border_disp_linestring_gen6)
 UNION ALL
 SELECT geometry,
        admin_level,
+       NULL::text AS adm0_l,
+       NULL::text AS adm0_r,
        TRUE AS disputed,
        edit_name(name) AS disputed_name,
        claimed_by,
@@ -429,16 +503,20 @@ CREATE OR REPLACE VIEW boundary_z9 AS
 (
 SELECT geometry,
        admin_level,
+       adm0_l,
+       adm0_r,
        disputed,
        NULL AS disputed_name,
        NULL AS claimed_by,
        maritime
 FROM osm_border_linestring_gen5
 WHERE admin_level <= 6
-  AND osm_id NOT IN (SELECT DISTINCT osm_id FROM osm_border_disp_linestring_gen5)
+-- AND osm_id NOT IN (SELECT DISTINCT osm_id FROM osm_border_disp_linestring_gen5)
 UNION ALL
 SELECT geometry,
        admin_level,
+       NULL::text AS adm0_l,
+       NULL::text AS adm0_r,
        TRUE AS disputed,
        edit_name(name) AS disputed_name,
        claimed_by,
@@ -452,16 +530,20 @@ CREATE OR REPLACE VIEW boundary_z10 AS
 (
 SELECT geometry,
        admin_level,
+       adm0_l,
+       adm0_r,
        disputed,
        NULL AS disputed_name,
        NULL AS claimed_by,
        maritime
 FROM osm_border_linestring_gen4
 WHERE admin_level <= 6
-  AND osm_id NOT IN (SELECT DISTINCT osm_id FROM osm_border_disp_linestring_gen4)
+-- AND osm_id NOT IN (SELECT DISTINCT osm_id FROM osm_border_disp_linestring_gen4)
 UNION ALL
 SELECT geometry,
        admin_level,
+       NULL::text AS adm0_l,
+       NULL::text AS adm0_r,
        TRUE AS disputed,
        edit_name(name) AS disputed_name,
        claimed_by,
@@ -475,16 +557,20 @@ CREATE OR REPLACE VIEW boundary_z11 AS
 (
 SELECT geometry,
        admin_level,
+       adm0_l,
+       adm0_r,
        disputed,
        NULL AS disputed_name,
        NULL AS claimed_by,
        maritime
 FROM osm_border_linestring_gen3
 WHERE admin_level <= 8
-  AND osm_id NOT IN (SELECT DISTINCT osm_id FROM osm_border_disp_linestring_gen3)
+-- AND osm_id NOT IN (SELECT DISTINCT osm_id FROM osm_border_disp_linestring_gen3)
 UNION ALL
 SELECT geometry,
        admin_level,
+       NULL::text AS adm0_l,
+       NULL::text AS adm0_r,
        TRUE AS disputed,
        edit_name(name) AS disputed_name,
        claimed_by,
@@ -498,15 +584,19 @@ CREATE OR REPLACE VIEW boundary_z12 AS
 (
 SELECT geometry,
        admin_level,
+       adm0_l,
+       adm0_r,
        disputed,
        NULL AS disputed_name,
        NULL AS claimed_by,
        maritime
 FROM osm_border_linestring_gen2
-WHERE osm_id NOT IN (SELECT DISTINCT osm_id FROM osm_border_disp_linestring_gen2)
+--WHERE osm_id NOT IN (SELECT DISTINCT osm_id FROM osm_border_disp_linestring_gen2)
 UNION ALL
 SELECT geometry,
        admin_level,
+       NULL::text AS adm0_l,
+       NULL::text AS adm0_r,
        TRUE AS disputed,
        edit_name(name) AS disputed_name,
        claimed_by,
@@ -520,15 +610,19 @@ CREATE OR REPLACE VIEW boundary_z13 AS
 (
 SELECT geometry,
        admin_level,
+       adm0_l,
+       adm0_r,
        disputed,
        NULL AS disputed_name,
        NULL AS claimed_by,
        maritime
 FROM osm_border_linestring_gen1
-WHERE osm_id NOT IN (SELECT DISTINCT osm_id FROM osm_border_disp_linestring_gen1)
+--WHERE osm_id NOT IN (SELECT DISTINCT osm_id FROM osm_border_disp_linestring_gen1)
 UNION ALL
 SELECT geometry,
        admin_level,
+       NULL::text AS adm0_l,
+       NULL::text AS adm0_r,
        TRUE AS disputed,
        edit_name(name) AS disputed_name,
        claimed_by,
@@ -543,6 +637,8 @@ CREATE OR REPLACE FUNCTION layer_boundary(bbox geometry, zoom_level int)
             (
                 geometry      geometry,
                 admin_level   int,
+                adm0_l        text,
+                adm0_r        text,
                 disputed      int,
                 disputed_name text,
                 claimed_by    text,
@@ -550,7 +646,7 @@ CREATE OR REPLACE FUNCTION layer_boundary(bbox geometry, zoom_level int)
             )
 AS
 $$
-SELECT geometry, admin_level, disputed::int, disputed_name, claimed_by, maritime::int
+SELECT geometry, admin_level, adm0_l, adm0_r, disputed::int, disputed_name, claimed_by, maritime::int
 FROM (
          -- etldoc: boundary_z0 ->  layer_boundary:z0
          SELECT *

layers/boundary/boundary.yaml

@@ -14,6 +14,10 @@ layer:
         The `admin_level` corresponds to the lowest `admin_level`
         the line participates in.
         At low zoom levels the Natural Earth boundaries are mapped to the equivalent admin levels.
+    adm0_l: |
+        State name on the left of the border. For country boundaries only (`admin_level = 2`).
+    adm0_r: |
+        State name on the right of the border. For country boundaries only (`admin_level = 2`).
     disputed:
       description: |
           Mark with `1` if the border is disputed.
@@ -46,8 +50,9 @@ layer:
   buffer_size: 4
   datasource:
     geometry_field: geometry
-    query: (SELECT geometry, admin_level, disputed, disputed_name, claimed_by, maritime FROM layer_boundary(!bbox!, z(!scale_denominator!))) AS t
+    query: (SELECT geometry, admin_level, adm0_l, adm0_r, disputed, disputed_name, claimed_by, maritime FROM layer_boundary(!bbox!, z(!scale_denominator!))) AS t
 schema:
+  - ./boundary_name.sql
   - ./boundary.sql
 datasources:
   - type: imposm3

layers/boundary/boundary_name.sql

@@ -0,0 +1,99 @@
+DROP TABLE IF EXISTS osm_border_linestring_adm CASCADE;
+
+-- etldoc: osm_border_linestring -> osm_border_linestring_adm
+CREATE TABLE IF NOT EXISTS osm_border_linestring_adm AS ( 
+  WITH 
+    -- Prepare lines from osm to be merged
+	multiline AS (
+    	SELECT ST_Node(ST_Collect(geometry)) AS geometry, 
+			   maritime,
+			   disputed
+    	FROM osm_border_linestring
+    	WHERE admin_level = 2
+		    AND osm_id NOT IN (SELECT DISTINCT osm_id FROM osm_border_disp_linestring)
+		GROUP BY maritime,
+				 disputed
+		),
+
+	mergedline AS (
+		SELECT (ST_Dump(
+      		     ST_LineMerge(geometry))).geom AS geometry,
+			maritime,
+			disputed
+  		FROM multiline
+		),
+    -- Create polygons from all boundaries to preserve real shape of country
+	polyg AS (
+    	SELECT (ST_Dump(
+        		 ST_Polygonize(geometry))).geom AS geometry  
+    	FROM (
+			SELECT (ST_Dump(
+      				ST_LineMerge(geometry))).geom AS geometry
+  			FROM (SELECT ST_Node(
+                          ST_Collect(geometry)) AS geometry
+    			FROM osm_border_linestring
+    			WHERE admin_level = 2
+                ) nodes
+			) linemerge
+  		), 
+
+    centroids AS (
+		SELECT polyg.geometry,
+			   ne.adm0_a3
+		FROM polyg,
+			 ne_10m_admin_0_countries AS ne
+		WHERE ST_Within(
+			   ST_PointOnSurface(polyg.geometry), ne.geometry)
+    	),
+
+	country_osm_polyg AS  (
+		SELECT country.adm0_a3,
+			   border.geometry
+  		FROM polyg border,
+			 centroids country
+  		WHERE ST_Within(country.geometry, border.geometry)
+	),
+
+	rights AS (
+    	SELECT adm0_r,
+			   geometry,
+			   maritime,
+			   disputed
+		FROM (
+			SELECT b.adm0_a3 AS adm0_r,
+                   a.geometry,
+                   a.maritime,
+                   a.disputed
+			FROM mergedline AS a
+			LEFT JOIN country_osm_polyg AS b
+            -- Create short line on the right of the boundary (mergedline) and find state where line lies.
+			ON ST_Within(
+				ST_OffsetCurve(
+				(ST_LineSubString(a.geometry, 0.3,0.3004)), 70, 'quad_segs=4 join=mitre'), b.geometry)
+            ) line_rights
+		)
+
+  SELECT adm0_l,
+		 adm0_r,
+		 geometry,
+		 maritime,
+		 2::integer AS admin_level,
+		 disputed
+  FROM (
+    SELECT b.adm0_a3 AS adm0_l,
+           r.adm0_r AS adm0_r,
+           r.geometry,
+           r.maritime,
+           r.disputed
+    FROM rights AS r
+    LEFT JOIN country_osm_polyg AS b
+      -- Create short line on the left of the boundary (mergedline) and find state where line lies.
+      ON ST_Within(
+        ST_OffsetCurve(
+          (ST_LineSubString(r.geometry, 0.4,0.4004)), -70, 'quad_segs=4 join=mitre'), b.geometry)
+    ) both_lines
+);
+
+CREATE INDEX IF NOT EXISTS osm_border_linestring_adm_geom_idx
+  ON osm_border_linestring_adm
+  USING GIST (geometry);