A CPV code is now stored once, keeping its longest description

internal/store/migrate_test.go

@@ -327,3 +327,78 @@ func TestFailedMigrationIsRolledBack(t *testing.T) {
 		t.Errorf("failed migration left %d objects behind", indexes)
 	}
 }
+
+// Migration 10 merges each CPV code's rows into the one with the longest
+// description, moving the links to it (one link if an opportunity had both),
+// and leaves other schemes' rows alone.
+func TestMigration10MergesCPVDuplicates(t *testing.T) {
+	ctx := context.Background()
+	m, db := newMigrator(t)
+	if _, err := m.UpTo(ctx, 9); err != nil {
+		t.Fatal(err)
+	}
+
+	const full = "Petroleum products, fuel, electricity and other sources of energy"
+	setup := []string{
+		`INSERT INTO opportunities (uuid, uuid_type, title, status, latest_release_date)
+		 VALUES ('a', 'ocid', 'A', 'active', '2026-10-01'),
+		        ('b', 'ocid', 'B', 'active', '2026-10-01')`,
+		`INSERT INTO classification_codes (id, is_cpv, code, classification) VALUES
+		 (1, 1, '09000000', '` + full + `'),
+		 (2, 1, '09000000', '` + full[:64] + `'),
+		 (3, 0, '123', 'Scheme X'),
+		 (4, 0, '123', 'Scheme X, amended')`,
+		// a links to both CPV rows, b only to the cut one.
+		`INSERT INTO opportunity_classifications VALUES
+		 ('a', 1), ('a', 2), ('b', 2), ('a', 3), ('b', 4)`,
+	}
+	for _, statement := range setup {
+		if _, err := db.ExecContext(ctx, statement); err != nil {
+			t.Fatal(err)
+		}
+	}
+
+	if _, err := m.UpTo(ctx, 10); err != nil {
+		t.Fatal(err)
+	}
+
+	var codes []string
+	rows, err := db.QueryContext(ctx,
+		`SELECT id || ':' || classification FROM classification_codes ORDER BY id`)
+	if err != nil {
+		t.Fatal(err)
+	}
+	for rows.Next() {
+		var code string
+		rows.Scan(&code)
+		codes = append(codes, code)
+	}
+	rows.Close()
+	want := "1:" + full + "|3:Scheme X|4:Scheme X, amended"
+	if got := strings.Join(codes, "|"); got != want {
+		t.Errorf("codes = %s; want %s", got, want)
+	}
+
+	var links []string
+	rows, err = db.QueryContext(ctx, `SELECT opportunity_uuid || classification_id
+		FROM opportunity_classifications ORDER BY 1`)
+	if err != nil {
+		t.Fatal(err)
+	}
+	for rows.Next() {
+		var link string
+		rows.Scan(&link)
+		links = append(links, link)
+	}
+	rows.Close()
+	if got := strings.Join(links, ","); got != "a1,a3,b1,b4" {
+		t.Errorf("links = %s; want a1,a3,b1,b4", got)
+	}
+
+	// A second row for the code is now refused.
+	_, err = db.ExecContext(ctx, `INSERT INTO classification_codes
+		(is_cpv, code, classification) VALUES (1, '09000000', 'Other')`)
+	if err == nil {
+		t.Error("a second row for a CPV code was accepted")
+	}
+}