Flash Back Version Query
参考文档：
http://docs.oracle.com/cd/E11882_01/appdev.112/e25518/adfns_flashback.htm
http://www.cnblogs.com/coohoo/archive/2011/01/16/1936888.html
Use Oracle Flashback Version Query to retrieve the different versions of specific rows that existed during a given time interval. A row version is created whenever a COMMIT statement is executed.
<!--[if !supportLists]-->1. <!--[endif]-->使用flashback query的前提
<!--[if !supportLists]-->Ø <!--[endif]-->undo_management = auto，设置自动undo管理（AUM），该参数默认设置为：auto；
查询语句：show parameter undo;
<!--[if !supportLists]-->Ø <!--[endif]-->设置足够大的undo_retention，undo_retention表示的是操作在undo表空间中保存的时间
<!--[if !supportLists]-->Ø <!--[endif]-->设置足够大的undo表空间大小
<!--[if !supportLists]-->2. <!--[endif]-->flashback query 的使用方法
<!--[if !supportLists]-->Ø <!--[endif]-->先用 select current_scn from V$database; 语句查出当前的scn值，记录为scn1
<!--[if !supportLists]-->Ø <!--[endif]-->执行一段insert，update，delete操作
<!--[if !supportLists]-->Ø <!--[endif]-->用 select current_scn from V$database; 语句查出操作执行完毕后的scn值，记录为scn2
<!--[if !supportLists]-->Ø <!--[endif]-->用语句
select versions_startscn,versions_endscn,versions_operation,<查询表的字段名> from <表名> versions between scn <操作开始前的scn> and <操作结束的scn> where versions_operation is not null
查出整个操作
示例数据：其中第一列为操作类型，后面为每列的数据
<!--[if !supportLists]-->3. <!--[endif]-->性能比较
为了做性能的比较，我在本地用client setting表做实验，表格中是trigger方式的DDL语句
| drop TABLE CLIENT_SETTING_INCREMENT; CREATE TABLE CLIENT_SETTING_INCREMENT ( "ACCOUNT_ID" NUMBER(19,0), "CONTENT_ID" NUMBER(*,0), "CONTEXT_ID" NUMBER(*,0), "PROPERTY_ID" NUMBER(*,0), "SETTING_TYPE" NUMBER(*,0), "SETTING_VALUE" VARCHAR2(4000 BYTE), CHANGE_FLAGS VARCHAR2(8 BYTE), --U for update, I for insert, D for delete. CONSTRAINT "CLIENT_SET_INC_CONST_PKEY" PRIMARY KEY ("ACCOUNT_ID", "CONTENT_ID", "CONTEXT_ID", "PROPERTY_ID") USING INDEX PCTFREE 10 INITRANS 2 MAXTRANS 255 COMPUTE STATISTICS STORAGE(INITIAL 65536 NEXT 1048576 MINEXTENTS 1 MAXEXTENTS 2147483645 PCTINCREASE 0 FREELISTS 1 FREELIST GROUPS 1 BUFFER_POOL DEFAULT) TABLESPACE "INDEX_LARGE" ENABLE, CONSTRAINT "CLIENT_SET_INC_AID_CONST_FKEY" FOREIGN KEY ("ACCOUNT_ID") REFERENCES "Z7ADMIN"."ACCOUNT" ("ID") ON DELETE CASCADE ENABLE );
--create a row level trigger to track the changes on CLIENT_SETTING drop trigger CLIENT_SETTING_INC_TRIGGER; CREATE OR REPLACE TRIGGER CLIENT_SETTING_INC_TRIGGER AFTER UPDATE OR DELETE OR INSERT ON CLIENT_SETTING FOR EACH ROW
DECLARE change_flags VARCHAR2(8); -- U, D, I num NUMBER(2,0);
BEGIN num := 0;
CASE WHEN UPDATING THEN select count(1) into num from CLIENT_SETTING_INCREMENT where ACCOUNT_ID=:NEW.ACCOUNT_ID and CONTENT_ID=:NEW.CONTENT_ID and CONTEXT_ID=:NEW.CONTEXT_ID and PROPERTY_ID = :NEW.PROPERTY_ID;
IF num > 0 THEN update CLIENT_SETTING_INCREMENT set SETTING_TYPE=:NEW.SETTING_TYPE ,SETTING_VALUE=:NEW.SETTING_VALUE , CHANGE_FLAGS='U' where ACCOUNT_ID=:NEW.ACCOUNT_ID and CONTENT_ID=:NEW.CONTENT_ID and CONTEXT_ID=:NEW.CONTEXT_ID and PROPERTY_ID = :NEW.PROPERTY_ID; ELSE Insert into CLIENT_SETTING_INCREMENT (ACCOUNT_ID,CONTENT_ID,CONTEXT_ID,PROPERTY_ID,SETTING_TYPE,SETTING_VALUE,CHANGE_FLAGS ) values (:NEW.ACCOUNT_ID, :NEW.CONTENT_ID, :NEW.CONTEXT_ID, :NEW.PROPERTY_ID, :NEW.SETTING_TYPE, :NEW.SETTING_VALUE, 'U'); END IF;
WHEN DELETING THEN select count(1) into num from CLIENT_SETTING_INCREMENT where ACCOUNT_ID=:OLD.ACCOUNT_ID and CONTENT_ID=:OLD.CONTENT_ID and CONTEXT_ID=:OLD.CONTEXT_ID and PROPERTY_ID = :OLD.PROPERTY_ID; dbms_output.put_line(num); IF num > 0 THEN update CLIENT_SETTING_INCREMENT set CHANGE_FLAGS='D' where ACCOUNT_ID=:OLD.ACCOUNT_ID and CONTENT_ID=:OLD.CONTENT_ID and CONTEXT_ID=:OLD.CONTEXT_ID and PROPERTY_ID = :OLD.PROPERTY_ID; ELSE Insert into CLIENT_SETTING_INCREMENT (ACCOUNT_ID,CONTENT_ID,CONTEXT_ID,PROPERTY_ID,SETTING_TYPE,SETTING_VALUE,CHANGE_FLAGS ) values (:OLD.ACCOUNT_ID, :OLD.CONTENT_ID, :OLD.CONTEXT_ID, :OLD.PROPERTY_ID, :OLD.SETTING_TYPE, :OLD.SETTING_VALUE, 'D');
END IF;
WHEN INSERTING THEN Insert into CLIENT_SETTING_INCREMENT (ACCOUNT_ID,CONTENT_ID,CONTEXT_ID,PROPERTY_ID,SETTING_TYPE,SETTING_VALUE,CHANGE_FLAGS ) values (:NEW.ACCOUNT_ID, :NEW.CONTENT_ID, :NEW.CONTEXT_ID, :NEW.PROPERTY_ID, :NEW.SETTING_TYPE, :NEW.SETTING_VALUE, 'I'); END CASE;
END; |
<!--[if !supportLists]-->Ø <!--[endif]-->CLIENT_SETTING_INCREMENT中1000000数据，10000操作
使用trigger 花费35621ms。
不使用trigger 花费31746ms。
<!--[if !supportLists]-->Ø <!--[endif]-->CLIENT_SETTING_INCREMENT中2000000数据，100000操作
使用trigger 花费372923。
不使用trigger 花费294024。
<!--[if !supportLists]-->4. <!--[endif]-->项目的应用
考虑到sinc map项目中trigger可能会影响用户操作的响应时间，我们是否能够用flashback来减少对用户操作的影响，用户操作的记录可以用以下语句得到，对每一行都只会得到最新的操作记录。
| select * from (select versions_operation,account_id,CONTENT_ID,CONTEXT_ID,PROPERTY_ID,SETTING_TYPE,SETTING_VALUE, RANK() OVER (PARTITION BY account_id,CONTENT_ID,CONTEXT_ID,PROPERTY_ID order by versions_startscn desc,versions_endscn desc) rank1 from z7admin.client_setting versions between scn 1005591 and 10405591 where versions_operation is not null) where rank1 = 1 |