1.创建logging模式,并且创建一个logging模式下的记录表:

CREATESCHEMAlogging;

CREATETABLElogging.user_history(
idserial,tstamptimestampDEFAULTnow(),schemanametext,tabnametext,operationtext,whotextDEFAULTcurrent_user,new_valjson,old_valjson
);

2.创建触发器函数:

CREATEFUNCTIONchange_user_trigger()
RETURNStriggerAS$$
BEGIN
IFTG_OP='INSERT'THEN
INSERTINTOlogging.user_history(tabname,schemaname,operation,new_val)values(TG_RELNAME,TG_TABLE_SCHEMA,TG_OP,row_to_json(NEW));
RETURNNEW;
ELSIFTG_OP='UPDATE'THEN
INSERTINTOlogging.user_history(tabname,new_val,old_val)values(TG_RELNAME,row_to_json(NEW),row_to_json(OLD));
RETURNNEW;
ELSIFTG_OP='DELETE'THEN
INSERTINTOlogging.user_history(tabname,row_to_json(OLD));
	RETURNOLD;--返回值要与ELSIF平齐,因为先插入后最好才执行返回
	ENDIF;
END;
$$LANGUAGE'plpgsql'SECURITYDEFINER;--securitydefiner是指定创建该函数用户的权限执行,securityinvoker是指以调用该函数用户发权限执行

3.创建测试表users:

CREATETABLEusers
(
idserialNOTNULL,usernamecharactervarying(40),emailcharactervarying(100)
)

4.创建触发器:

CREATETRIGGER"logging_user_change"
BEFOREINSERTORUPDATEORDELETE
ONusers
FOREACHROW
EXECUTEPROCEDUREchange_user_trigger();

5.测试：

INSERTINTOusersVALUES('hans','hans@qq.com');
UPDATEuseRSSETid=1,username='paul';

这个函数的缺陷:

1,它不能监控select语句

2,它不能监控系统表

3,它不能监控DDL操作,例如alter table(如果需要监控可以配置postgresql.conf文件,修改log_statment参数:#log_statement = 'none' # none,ddl,mod,all)