--创建触发器函数
create or replace function abort_any_command()
returns event_trigger
language plpgsql
as $$
begin
raise exception 'command % is disabled ',tg_tag;
end;
$$;

--创建触发器
create event trigger abort_ddl on ddl_command_start
execute procedure abort_any_command();

--测试触发器
test=# drop table emp;
ERROR:  command DROP TABLE is disabled
CONTEXT:  PL/pgSQL function abort_any_command() line 3 at RAISE
test=# create table emp01 (x int);
ERROR:  command CREATE TABLE is disabled
CONTEXT:  PL/pgSQL function abort_any_command() line 3 at RAISEtest=# truncate table emp;  --注意：truncate是在普通触发器中触发，在事件触发器中不会触发。
TRUNCATE TABLE--恢复DDL正常操作

test=# alter event trigger abort_ddl disable;
ALTER EVENT TRIGGER

--创建审计记录表
create table log_drop_objects(
op_time         timestamp, --操作执行时间
ddl_tag         text,  --执行的ddl操作
classid         Oid,
objid           Oid,
objsubid        OID,
object_type     text,
schema_name     text,
object_name     text,
object_identify text
);--创建触发器函数
create function event_trigger_log_drops()
returns event_trigger language plpgsql as $$
declare
obj record;
begin
insert into log_drop_objects select now(),tg_tag,classid,objid,objsubid,
object_type,schema_name,object_name,
object_identity from pg_event_trigger_dropped_objects();
end
$$;--创建触发器
create event trigger event_trigger_log_drops
on sql_drop
execute procedure event_trigger_log_drops();--测试触发器
test=# alter table emp drop column salary;
ALTER TABLE
test=#
test=# select ddl_tag,object_type,object_name,object_identity from log_drop_objects;ddl_tag   | object_type  | object_name |  object_identity
-------------+--------------+-------------+-------------------ALTER TABLE | table column |             | public.emp.salary
(1 row)test=#
test=# drop table emp;
DROP TABLE
test=#
test=# select ddl_tag,object_type,object_name,object_identity from log_drop_objects;ddl_tag   | object_type  |     object_name      |        object_identity
-------------+--------------+----------------------+-------------------------------ALTER TABLE | table column |                      | public.emp.salaryDROP TABLE  | table        | emp                  | public.empDROP TABLE  | type         | emp                  | public.empDROP TABLE  | type         | _emp                 | public.emp[]DROP TABLE  | toast table  | pg_toast_16461       | pg_toast.pg_toast_16461DROP TABLE  | index        | pg_toast_16461_index | pg_toast.pg_toast_16461_indexDROP TABLE  | type         | pg_toast_16461       | pg_toast.pg_toast_16461DROP TABLE  | trigger      |                      | emp_audit on public.emp
(8 rows)

ALTER EVENT TRIGGER name DISABLE
ALTER EVENT TRIGGER name ENABLE [ REPLICA | ALWAYS ]
ALTER EVENT TRIGGER name OWNER TO new_owner
ALTER EVENT TRIGGER name RENAME TO new_name