你必须查询元数据：

CREATE OR REPLACE FUNCTION changed_columns() RETURNS trigger
   LANGUAGE plpgsql AS
$$DECLARE
   col name;
   changed_cols text[] := ARRAY[]::text[];
   changed boolean;
BEGIN
   FOR col IN
      /* get the columns of the table */
      SELECT attname
      FROM pg_attribute
      WHERE attrelid = TG_RELID
        AND attnum > 0
        AND NOT attisdropped
   LOOP
      /* compare the column in OLD and NEW */
      EXECUTE
         format(
            'SELECT (($1::%1$s).%2$I) IS DISTINCT FROM (($2::%1$s).%2$I)',
            TG_RELID::regclass,
            col
         )
         USING OLD, NEW
         INTO changed;

      IF changed THEN
         changed_cols := changed_cols || col::text;
      END IF;
   END LOOP;

   RAISE NOTICE 'changed columns: %',
                array_to_string(changed_cols, ', ');

   /* proceed with the UPDATE */
   RETURN NEW;
END;$$;

下面是一个基于JSONB的建议。将new和old转换为JSONB，以便提取键（这些是表的列名）并迭代它们。

create or replace function changed_columns()
returns trigger language plpgsql as
$function$
declare
  new_jb jsonb := to_jsonb(new); 
  old_jb jsonb := to_jsonb(old); 
  running_column text;
  columns_list text[] := '{}';
begin
 for running_column in select jsonb_object_keys(new_jb) loop
   if (new_jb -> running_column <> old_jb -> running_column) then
     columns_list := columns_list || running_column;
   end if;
 end loop;
 raise notice 'changed columns: %', array_to_string(columns_list, ',');
 -- or use columns_list for something more useful
 return null; -- use it in an after update trigger
end;
$function$;