# 触发器函数
- pg_get_triggerdef(oid) 描述：获取触发器的定义信息。
  参数：待查触发器的OID。
  返回值类型：text
  示例:
  ```
  -- 创建表tri_insert。
  gaussdb=# CREATE TABLE tri_insert (a int, b int);
  CREATE TABLE
  -- 创建函数trigger_func。
  gaussdb=# CREATE FUNCTION trigger_func() RETURNS trigger LANGUAGE plpgsql AS '
  gaussdb'# BEGIN
  gaussdb'# RAISE NOTICE ''trigger_func(%) called: action = %, when = %, level = %'', TG_ARGV[0], TG_OP, TG_WHEN, TG_LEVEL;
  gaussdb'# RETURN NULL;
  gaussdb'# END;';
  CREATE FUNCTION
  -- 创建触发器before_ins_stmt_trig。
  gaussdb=# CREATE TRIGGER before_ins_stmt_trig BEFORE INSERT ON tri_insert
  gaussdb-# FOR EACH STATEMENT EXECUTE PROCEDURE trigger_func('before_ins_stmt');
  CREATE TRIGGER
  -- 创建触发器after_ins_when_trig。
  gaussdb=# CREATE TRIGGER after_ins_when_trig AFTER INSERT ON tri_insert
  gaussdb-# FOR EACH ROW WHEN (new.a IS NOT NULL) EXECUTE PROCEDURE trigger_func('after_ins_when');
  CREATE TRIGGER
  -- 查看表tri_insert的触发器定义信息。
  gaussdb=# SELECT pg_get_triggerdef(oid) FROM pg_trigger WHERE tgrelid = 'tri_insert'::regclass;
                                                                     pg_get_triggerdef                                                                    
  --------------------------------------------------------------------------------------------------------------------------------------------------------
   CREATE TRIGGER before_ins_stmt_trig BEFORE INSERT ON tri_insert FOR EACH STATEMENT EXECUTE PROCEDURE trigger_func('before_ins_stmt')
   CREATE TRIGGER after_ins_when_trig AFTER INSERT ON tri_insert FOR EACH ROW WHEN ((new.a IS NOT NULL)) EXECUTE PROCEDURE trigger_func('after_ins_when')
  (2 rows)
  ```
  
- pg_get_triggerdef(oid, boolean) 描述：获取触发器的定义信息。
  参数：待查触发器的OID及是否以pretty方式展示。
  ![](https://support.huaweicloud.com/centralized-devg-v3-gaussdb/public_sys-resources/note_3.0-zh-cn.png)
  仅在创建trigger时指定WHEN条件的情况下，布尔类型参数才生效。
  返回值类型：text
  示例:
  ```
  -- 查看表tri_insert的触发器定义信息，以非pretty形式。
  gaussdb=# SELECT pg_get_triggerdef(oid, false) FROM pg_trigger WHERE tgrelid = 'tri_insert'::regclass;
                                                                     pg_get_triggerdef                                                                    
  --------------------------------------------------------------------------------------------------------------------------------------------------------
   CREATE TRIGGER before_ins_stmt_trig BEFORE INSERT ON tri_insert FOR EACH STATEMENT EXECUTE PROCEDURE trigger_func('before_ins_stmt')
   CREATE TRIGGER after_ins_when_trig AFTER INSERT ON tri_insert FOR EACH ROW WHEN ((new.a IS NOT NULL)) EXECUTE PROCEDURE trigger_func('after_ins_when')
  (2 rows)
  -- 查看表tri_insert的触发器定义信息，以pretty形式。
  gaussdb=# SELECT pg_get_triggerdef(oid, true) FROM pg_trigger WHERE tgrelid = 'tri_insert'::regclass;
                                                                    pg_get_triggerdef                                                                   
  ------------------------------------------------------------------------------------------------------------------------------------------------------
   CREATE TRIGGER before_ins_stmt_trig BEFORE INSERT ON tri_insert FOR EACH STATEMENT EXECUTE PROCEDURE trigger_func('before_ins_stmt')
   CREATE TRIGGER after_ins_when_trig AFTER INSERT ON tri_insert FOR EACH ROW WHEN (new.a IS NOT NULL) EXECUTE PROCEDURE trigger_func('after_ins_when')
  (2 rows)
  -- 清理表tri_insert。
  gaussdb=# DROP TABLE tri_insert CASCADE;
  DROP TABLE
  -- 清理函数trigger_func。
  gaussdb=# DROP FUNCTION trigger_func;
  DROP FUNCTION
  ```