Alexey Trigubin

INSERT INTO table (id, chtoto) VALUES (74291910, array_append(chtoto, 'string') 
ON CONFLICT (id) DO UPDATE SET chtoto=EXCLUDED.chtoto

INSERT INTO tbl (id, chtoto) VALUES (74291910, array['string'])
ON CONFLICT (id) DO UPDATE SET chtoto=array_append(tbl.chtoto, 'string');
								 
INSERT INTO tbl (id, chtoto) VALUES (74291910, array['string2'])
ON CONFLICT (id) DO UPDATE SET chtoto=array_append(tbl.chtoto, 'string2');

+==========+==================+
| id       | chtoto           |
+==========+==================+
| 74291910 | {string,string2} |
+----------+------------------+