CREATE EXTENSION test_copy_callbacks;
CREATE TABLE public.test (a INT, b INT, c INT);
INSERT INTO public.test VALUES (1, 2, 3), (12, 34, 56), (123, 456, 789);
SELECT test_copy_to_callback('public.test'::pg_catalog.regclass);
NOTICE:  COPY TO callback called with data "1	2	3" and length 5
NOTICE:  COPY TO callback called with data "12	34	56" and length 8
NOTICE:  COPY TO callback called with data "123	456	789" and length 11
NOTICE:  COPY TO callback has processed 3 rows
 test_copy_to_callback 
-----------------------
 
(1 row)