DROP EXTENSION IF EXISTS www_fdw CASCADE; CREATE EXTENSION www_fdw; CREATE SERVER www_fdw_server_test FOREIGN DATA WRAPPER www_fdw OPTIONS (uri 'http://localhost:7777', response_type 'json', response_iterate_callback 'test_response_iterate_callback'); CREATE USER MAPPING FOR current_user SERVER www_fdw_server_test; CREATE FOREIGN TABLE www_fdw_test ( title text, link text, snippet text ) SERVER www_fdw_server_test; CREATE OR REPLACE FUNCTION test_response_iterate_callback(options WWWFdwOptions, INOUT tuple www_fdw_test) AS $$ BEGIN RAISE DEBUG 'options parameter: %', options; RAISE DEBUG 'tuple parameter: %', tuple; tuple.title := tuple.title || ' hello world of callbacks'; END; $$ LANGUAGE PLPGSQL;