diff --git a/layers/aerodrome_label/layer.sql b/layers/aerodrome_label/layer.sql
index 4e91cc2..19e9bac 100644
--- a/layers/aerodrome_label/layer.sql
+++ b/layers/aerodrome_label/layer.sql
@@ -36,5 +36,6 @@ $$
     round(substring(ele from E'^(-?\\d+)(\\D|$)')::int*3.2808399)::int AS ele_ft
   FROM osm_aerodrome_label_point
   WHERE geometry && bbox AND zoom_level >= 10;
-
-$$ LANGUAGE SQL IMMUTABLE;
+$$
+LANGUAGE SQL
+IMMUTABLE PARALLEL SAFE;
diff --git a/layers/aeroway/layer.sql b/layers/aeroway/layer.sql
index c182a62..1116c67 100644
--- a/layers/aeroway/layer.sql
+++ b/layers/aeroway/layer.sql
@@ -40,4 +40,6 @@ RETURNS TABLE(geometry geometry, class text, ref text) AS $$
         FROM osm_aeroway_polygon WHERE zoom_level >= 14
     ) AS zoom_levels
     WHERE geometry && bbox;
-$$ LANGUAGE SQL IMMUTABLE;
+$$
+LANGUAGE SQL IMMUTABLE
+PARALLEL SAFE;
diff --git a/layers/boundary/boundary.sql b/layers/boundary/boundary.sql
index 614d48e..1b0c318 100644
--- a/layers/boundary/boundary.sql
+++ b/layers/boundary/boundary.sql
@@ -470,4 +470,6 @@ RETURNS TABLE(geometry geometry, admin_level int, disputed int, disputed_name te
         -- etldoc: boundary_z13 -> layer_boundary:z13
         SELECT * FROM boundary_z13 WHERE geometry && bbox AND zoom_level >= 13
     ) AS zoom_levels;
-$$ LANGUAGE SQL IMMUTABLE;
+$$
+LANGUAGE SQL IMMUTABLE
+PARALLEL SAFE;
diff --git a/layers/building/building.sql b/layers/building/building.sql
index 4efd65d..14a48df 100644
--- a/layers/building/building.sql
+++ b/layers/building/building.sql
@@ -142,6 +142,8 @@ RETURNS TABLE(geometry geometry, osm_id bigint, render_height int, render_min_he
             zoom_level >= 14 AND geometry && bbox
     ) AS zoom_levels
     ORDER BY render_height ASC, ST_YMin(geometry) DESC;
-$$ LANGUAGE SQL IMMUTABLE;
+$$
+LANGUAGE SQL IMMUTABLE
+PARALLEL SAFE;
 
 -- not handled: where a building outline covers building parts
diff --git a/layers/housenumber/layer.sql b/layers/housenumber/layer.sql
index eed865f..01f2649 100644
--- a/layers/housenumber/layer.sql
+++ b/layers/housenumber/layer.sql
@@ -7,4 +7,6 @@ RETURNS TABLE(osm_id bigint, geometry geometry, housenumber text) AS $$
    -- etldoc: osm_housenumber_point -> layer_housenumber:z14_
     SELECT osm_id, geometry, housenumber FROM osm_housenumber_point
     WHERE zoom_level >= 14 AND geometry && bbox;
-$$ LANGUAGE SQL IMMUTABLE;
+$$
+LANGUAGE SQL
+IMMUTABLE PARALLEL SAFE;
diff --git a/layers/landcover/landcover.sql b/layers/landcover/landcover.sql
index 7bc0fb7..3fb62b6 100644
--- a/layers/landcover/landcover.sql
+++ b/layers/landcover/landcover.sql
@@ -13,7 +13,9 @@ CREATE OR REPLACE FUNCTION landcover_class(subclass VARCHAR) RETURNS TEXT AS $$
     SELECT CASE
         %%FIELD_MAPPING: class %%
     END;
-$$ LANGUAGE SQL IMMUTABLE;
+$$
+LANGUAGE SQL
+IMMUTABLE PARALLEL SAFE;
 
 -- etldoc: ne_110m_glaciated_areas ->  landcover_z0
 CREATE OR REPLACE VIEW landcover_z0 AS (
@@ -128,4 +130,6 @@ RETURNS TABLE(osm_id bigint, geometry geometry, class text, subclass text) AS $$
         SELECT *
         FROM landcover_z14 WHERE zoom_level >= 14 AND geometry && bbox
     ) AS zoom_levels;
-$$ LANGUAGE SQL IMMUTABLE;
+$$
+LANGUAGE SQL
+IMMUTABLE PARALLEL SAFE;
diff --git a/layers/landuse/landuse.sql b/layers/landuse/landuse.sql
index 252247f..14732f9 100644
--- a/layers/landuse/landuse.sql
+++ b/layers/landuse/landuse.sql
@@ -108,4 +108,6 @@ RETURNS TABLE(osm_id bigint, geometry geometry, class text) AS $$
         SELECT * FROM landuse_z14 WHERE zoom_level >= 14
     ) AS zoom_levels
     WHERE geometry && bbox;
-$$ LANGUAGE SQL IMMUTABLE;
+$$
+LANGUAGE SQL
+IMMUTABLE PARALLEL SAFE;
diff --git a/layers/mountain_peak/layer.sql b/layers/mountain_peak/layer.sql
index 6002bd1..9bbeec1 100644
--- a/layers/mountain_peak/layer.sql
+++ b/layers/mountain_peak/layer.sql
@@ -52,4 +52,6 @@ $$
   WHERE zoom_level >= 7 AND (rank <= 5 OR zoom_level >= 14)
   ORDER BY "rank" ASC;
 
-$$ LANGUAGE SQL IMMUTABLE;
+$$
+LANGUAGE SQL
+IMMUTABLE PARALLEL SAFE;
diff --git a/layers/park/layer.sql b/layers/park/layer.sql
index f3da111..3b49ce4 100644
--- a/layers/park/layer.sql
+++ b/layers/park/layer.sql
@@ -122,4 +122,6 @@ RETURNS TABLE(osm_id bigint, geometry geometry, class text, name text, name_en t
         WHERE zoom_level >= 14 AND geometry_point && bbox
     ) AS park_point
     ) AS park_all;
-$$ LANGUAGE SQL IMMUTABLE;
+$$
+LANGUAGE SQL
+IMMUTABLE PARALLEL SAFE;
diff --git a/layers/place/capital.sql b/layers/place/capital.sql
index 85fc7ea..434d3fb 100644
--- a/layers/place/capital.sql
+++ b/layers/place/capital.sql
@@ -4,4 +4,6 @@ RETURNS INT AS $$
         WHEN capital IN ('yes', '2') THEN 2
         WHEN capital = '4' THEN 4
     END;
-$$ LANGUAGE SQL IMMUTABLE STRICT;
+$$
+LANGUAGE SQL
+IMMUTABLE STRICT PARALLEL SAFE;
diff --git a/layers/place/city.sql b/layers/place/city.sql
index 59b6286..e3ef2d6 100644
--- a/layers/place/city.sql
+++ b/layers/place/city.sql
@@ -52,4 +52,6 @@ RETURNS TABLE(osm_id bigint, geometry geometry, name text, name_en text, name_de
        OR (zoom_level BETWEEN 11 AND 12 AND (gridrank <= 14 OR "rank" IS NOT NULL))
        OR (zoom_level >= 13)
   ) as city_all;
-$$ LANGUAGE SQL IMMUTABLE;
+$$
+LANGUAGE SQL
+IMMUTABLE PARALLEL SAFE;
diff --git a/layers/place/island_rank.sql b/layers/place/island_rank.sql
index 9d63124..15b8d5a 100644
--- a/layers/place/island_rank.sql
+++ b/layers/place/island_rank.sql
@@ -6,4 +6,6 @@ CREATE OR REPLACE FUNCTION island_rank(area REAL) RETURNS INT AS $$
         WHEN area > 40000000 THEN 3
         ELSE 7
     END;
-$$ LANGUAGE SQL IMMUTABLE STRICT;
+$$
+LANGUAGE SQL
+IMMUTABLE STRICT PARALLEL SAFE;
diff --git a/layers/place/layer.sql b/layers/place/layer.sql
index dd6381f..f4d3d40 100644
--- a/layers/place/layer.sql
+++ b/layers/place/layer.sql
@@ -96,4 +96,6 @@ RETURNS TABLE(osm_id bigint, geometry geometry, name text, name_en text,
     FROM layer_city(bbox, zoom_level, pixel_width)
     ORDER BY "rank" ASC
     ) AS place_all
-$$ LANGUAGE SQL IMMUTABLE;
+$$
+LANGUAGE SQL
+IMMUTABLE PARALLEL SAFE;
diff --git a/layers/poi/class.sql b/layers/poi/class.sql
index 74c3190..eea2319 100644
--- a/layers/poi/class.sql
+++ b/layers/poi/class.sql
@@ -25,7 +25,9 @@ RETURNS INT AS $$
         WHEN 'bar' THEN 800
         ELSE 1000
     END;
-$$ LANGUAGE SQL IMMUTABLE;
+$$
+LANGUAGE SQL
+IMMUTABLE PARALLEL SAFE;
 
 CREATE OR REPLACE FUNCTION poi_class(subclass TEXT, mapping_key TEXT)
 RETURNS TEXT AS $$
@@ -33,4 +35,6 @@ RETURNS TEXT AS $$
         %%FIELD_MAPPING: class %%
         ELSE subclass
     END;
-$$ LANGUAGE SQL IMMUTABLE;
+$$
+LANGUAGE SQL
+IMMUTABLE PARALLEL SAFE;
diff --git a/layers/poi/layer.sql b/layers/poi/layer.sql
index 29218cc..35c80e2 100644
--- a/layers/poi/layer.sql
+++ b/layers/poi/layer.sql
@@ -70,4 +70,6 @@ RETURNS TABLE(osm_id bigint, geometry geometry, name text, name_en text, name_de
         ) as poi_union
     ORDER BY "rank"
     ;
-$$ LANGUAGE SQL IMMUTABLE;
+$$
+LANGUAGE SQL
+IMMUTABLE PARALLEL SAFE;
diff --git a/layers/transportation/class.sql b/layers/transportation/class.sql
index 0bf33ae..43642ba 100644
--- a/layers/transportation/class.sql
+++ b/layers/transportation/class.sql
@@ -4,7 +4,9 @@ CREATE OR REPLACE FUNCTION brunnel(is_bridge BOOL, is_tunnel BOOL, is_ford BOOL)
         WHEN is_tunnel THEN 'tunnel'
         WHEN is_ford THEN 'ford'
     END;
-$$ LANGUAGE SQL IMMUTABLE STRICT;
+$$
+LANGUAGE SQL
+IMMUTABLE STRICT PARALLEL SAFE;
 
 -- The classes for highways are derived from the classes used in ClearTables
 -- https://github.com/ClearTables/ClearTables/blob/master/transportation.lua
@@ -12,7 +14,9 @@ CREATE OR REPLACE FUNCTION highway_class(highway TEXT, public_transport TEXT, co
     SELECT CASE
         %%FIELD_MAPPING: class %%
     END;
-$$ LANGUAGE SQL IMMUTABLE;
+$$
+LANGUAGE SQL
+IMMUTABLE PARALLEL SAFE;
 
 -- The classes for railways are derived from the classes used in ClearTables
 -- https://github.com/ClearTables/ClearTables/blob/master/transportation.lua
@@ -21,7 +25,9 @@ CREATE OR REPLACE FUNCTION railway_class(railway TEXT) RETURNS TEXT AS $$
         WHEN railway IN ('rail', 'narrow_gauge', 'preserved', 'funicular') THEN 'rail'
         WHEN railway IN ('subway', 'light_rail', 'monorail', 'tram') THEN 'transit'
     END;
-$$ LANGUAGE SQL IMMUTABLE STRICT;
+$$
+LANGUAGE SQL
+IMMUTABLE STRICT PARALLEL SAFE;
 
 -- Limit service to only the most important values to ensure
 -- we always know the values of service
@@ -29,7 +35,9 @@ CREATE OR REPLACE FUNCTION service_value(service TEXT) RETURNS TEXT AS $$
     SELECT CASE
         WHEN service IN ('spur', 'yard', 'siding', 'crossover', 'driveway', 'alley', 'parking_aisle') THEN service
     END;
-$$ LANGUAGE SQL IMMUTABLE STRICT;
+$$
+LANGUAGE SQL
+IMMUTABLE STRICT PARALLEL SAFE;
 
 -- Limit surface to only the most important values to ensure
 -- we always know the values of surface
@@ -38,4 +46,6 @@ CREATE OR REPLACE FUNCTION surface_value(surface TEXT) RETURNS TEXT AS $$
         WHEN surface IN ('paved', 'asphalt', 'cobblestone', 'concrete', 'concrete:lanes', 'concrete:plates', 'metal', 'paving_stones', 'sett', 'unhewn_cobblestone', 'wood') THEN 'paved'
         WHEN surface IN ('unpaved', 'compacted', 'dirt', 'earth', 'fine_gravel', 'grass', 'grass_paver', 'gravel', 'gravel_turf', 'ground', 'ice', 'mud', 'pebblestone', 'salt', 'sand', 'snow', 'woodchips') THEN 'unpaved'
     END;
-$$ LANGUAGE SQL IMMUTABLE STRICT;
+$$
+LANGUAGE SQL
+IMMUTABLE STRICT PARALLEL SAFE;
diff --git a/layers/transportation/layer.sql b/layers/transportation/layer.sql
index 0c60180..4b8bd88 100644
--- a/layers/transportation/layer.sql
+++ b/layers/transportation/layer.sql
@@ -1,6 +1,8 @@
 CREATE OR REPLACE FUNCTION highway_is_link(highway TEXT) RETURNS BOOLEAN AS $$
     SELECT highway LIKE '%_link';
-$$ LANGUAGE SQL IMMUTABLE STRICT;
+$$
+LANGUAGE SQL
+IMMUTABLE STRICT PARALLEL SAFE;
 
 
 -- etldoc: layer_transportation[shape=record fillcolor=lightpink, style="rounded,filled",
@@ -366,4 +368,6 @@ indoor INT, bicycle TEXT, foot TEXT, horse TEXT, mtb_scale TEXT, surface TEXT) A
     ) AS zoom_levels
     WHERE geometry && bbox
     ORDER BY z_order ASC;
-$$ LANGUAGE SQL IMMUTABLE;
+$$
+LANGUAGE SQL
+IMMUTABLE PARALLEL SAFE;
diff --git a/layers/transportation_name/layer.sql b/layers/transportation_name/layer.sql
index 29650bd..ffc3a3d 100644
--- a/layers/transportation_name/layer.sql
+++ b/layers/transportation_name/layer.sql
@@ -126,4 +126,6 @@ RETURNS TABLE(osm_id bigint, geometry geometry, name text, name_en text,
     ) AS zoom_levels
     WHERE geometry && bbox
     ORDER BY z_order ASC;
-$$ LANGUAGE SQL IMMUTABLE;
+$$
+LANGUAGE SQL
+IMMUTABLE PARALLEL SAFE;
diff --git a/layers/water/water.sql b/layers/water/water.sql
index 416134e..a478428 100644
--- a/layers/water/water.sql
+++ b/layers/water/water.sql
@@ -48,7 +48,9 @@ CREATE OR REPLACE FUNCTION water_class(waterway TEXT) RETURNS TEXT AS $$
            %%FIELD_MAPPING: class %%
            ELSE 'river'
    END;
-$$ LANGUAGE SQL IMMUTABLE;
+$$
+LANGUAGE SQL
+IMMUTABLE PARALLEL SAFE;
 
 
 CREATE OR REPLACE FUNCTION waterway_brunnel(is_bridge BOOL, is_tunnel BOOL) RETURNS TEXT AS $$
@@ -56,7 +58,9 @@ CREATE OR REPLACE FUNCTION waterway_brunnel(is_bridge BOOL, is_tunnel BOOL) RETU
         WHEN is_bridge THEN 'bridge'
         WHEN is_tunnel THEN 'tunnel'
     END;
-$$ LANGUAGE SQL IMMUTABLE STRICT;
+$$
+LANGUAGE SQL
+IMMUTABLE STRICT PARALLEL SAFE;
 
 
 
@@ -375,4 +379,6 @@ RETURNS TABLE(geometry geometry, class text, brunnel text, intermittent int) AS
         SELECT * FROM water_z14 WHERE zoom_level >= 14
     ) AS zoom_levels
     WHERE geometry && bbox;
-$$ LANGUAGE SQL IMMUTABLE;
+$$
+LANGUAGE SQL
+IMMUTABLE PARALLEL SAFE;
diff --git a/layers/water_name/layer.sql b/layers/water_name/layer.sql
index e0b60cd..0aab292 100644
--- a/layers/water_name/layer.sql
+++ b/layers/water_name/layer.sql
@@ -54,4 +54,6 @@ RETURNS TABLE(osm_id bigint, geometry geometry, name text, name_en text, name_de
         OR (zoom_level >= "rank" AND "rank" IS NOT NULL)
         OR (zoom_level >= 8)
     );
-$$ LANGUAGE SQL IMMUTABLE;
+$$
+LANGUAGE SQL
+IMMUTABLE PARALLEL SAFE;
diff --git a/layers/waterway/waterway.sql b/layers/waterway/waterway.sql
index a452115..35c277f 100644
--- a/layers/waterway/waterway.sql
+++ b/layers/waterway/waterway.sql
@@ -3,7 +3,9 @@ CREATE OR REPLACE FUNCTION waterway_brunnel(is_bridge BOOL, is_tunnel BOOL) RETU
         WHEN is_bridge THEN 'bridge'
         WHEN is_tunnel THEN 'tunnel'
     END;
-$$ LANGUAGE SQL IMMUTABLE STRICT;
+$$
+LANGUAGE SQL
+IMMUTABLE STRICT PARALLEL SAFE;
 
 -- etldoc: ne_110m_rivers_lake_centerlines ->  waterway_z3
 CREATE OR REPLACE VIEW waterway_z3 AS (
@@ -105,4 +107,6 @@ RETURNS TABLE(geometry geometry, class text, name text, name_en text, name_de te
         SELECT * FROM waterway_z14 WHERE zoom_level >= 14
     ) AS zoom_levels
     WHERE geometry && bbox;
-$$ LANGUAGE SQL IMMUTABLE;
+$$
+LANGUAGE SQL
+IMMUTABLE PARALLEL SAFE;