--- a/schema/gemma.sql	Wed Dec 12 17:21:11 2018 +0100
+++ b/schema/gemma.sql	Wed Dec 12 19:21:02 2018 +0100
@@ -402,7 +402,8 @@
     -- (minOccurs=0; nillable seems to be set arbitrarily as even bottleneck_id and
     -- fk_g_fid (both mandatory, i.e. marked "M" in DRC) have nillable="true" in WSDL)
     CREATE TABLE bottlenecks (
-        bottleneck_id varchar PRIMARY KEY,
+        id int PRIMARY KEY GENERATED BY DEFAULT AS IDENTITY,
+        bottleneck_id varchar UNIQUE NOT NULL,
         fk_g_fid isrs NOT NULL REFERENCES gauges,
         -- XXX: DRC references "ch. 3.1.1", which does not exist in document.
         objnam varchar,
@@ -431,7 +432,7 @@
         FOR EACH ROW EXECUTE PROCEDURE update_date_info()
 
     CREATE TABLE bottlenecks_riverbed_materials (
-        bottleneck_id varchar REFERENCES bottlenecks,
+        bottleneck_id int REFERENCES bottlenecks(id),
         riverbed varchar REFERENCES riverbed_materials,
         -- XXX: should be 'natsur' according to IENC Encoding Guide M.4.3
         PRIMARY KEY (bottleneck_id, riverbed)
@@ -439,7 +440,7 @@
 
     CREATE TABLE sounding_results (
         id int PRIMARY KEY GENERATED BY DEFAULT AS IDENTITY,
-        bottleneck_id varchar NOT NULL REFERENCES bottlenecks,
+        bottleneck_id int NOT NULL REFERENCES bottlenecks(id),
         date_info date NOT NULL,
         UNIQUE (bottleneck_id, date_info),
         area geography(POLYGON, 4326) NOT NULL,
@@ -476,7 +477,7 @@
     CREATE TABLE fairway_availability (
         id int PRIMARY KEY GENERATED BY DEFAULT AS IDENTITY,
         position_code char(2) REFERENCES position_codes,
-        bottleneck_id varchar NOT NULL REFERENCES bottlenecks,
+        bottleneck_id int NOT NULL REFERENCES bottlenecks(id),
         surdat date NOT NULL,
         UNIQUE (bottleneck_id, surdat),
         -- additional_data xml -- Currently not relevant for GEMMA
@@ -539,7 +540,7 @@
     FROM waterway.bottlenecks bn LEFT JOIN (
       SELECT bottleneck_id, max(date_info) AS current FROM
       waterway.sounding_results
-      GROUP BY bottleneck_id) sr ON sr.bottleneck_id = bn.bottleneck_id
+      GROUP BY bottleneck_id) sr ON sr.bottleneck_id = bn.id
     ORDER BY objnam
 
     CREATE TABLE import_configuration (