# 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) distribute by hash(a);
CREATE TABLE
-- 创建函数trigger_func。
gaussdb=# CREATE FUNCTION trigger_func() RETURNS trigger LANGUAGE plpgsql AS '
 BEGIN
 RAISE NOTICE ''trigger_func(%) called: action = %, when = %, level = %'', TG_ARGV[0], TG_OP, TG_WHEN, TG_LEVEL;
 RETURN NULL;
 END;';
CREATE FUNCTION
-- 创建触发器before_ins_stmt_trig。
gaussdb=# CREATE TRIGGER before_ins_stmt_trig BEFORE INSERT ON tri_insert 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 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 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')
 CREATE TRIGGER before_ins_stmt_trig BEFORE INSERT ON tri_insert FOR EACH STATEMENT EXECUTE PROCEDURE trigger_func('before_ins_stmt')
(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/distributed-devg-v8-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 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')
 CREATE TRIGGER before_ins_stmt_trig BEFORE INSERT ON tri_insert FOR EACH STATEMENT EXECUTE PROCEDURE trigger_func('before_ins_stmt')
(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 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')
 CREATE TRIGGER before_ins_stmt_trig BEFORE INSERT ON tri_insert FOR EACH STATEMENT EXECUTE PROCEDURE trigger_func('before_ins_stmt')
(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
```