闪回之闪回表（flashback table）

Posted 2020-08-27 张冲andy

背景知识


设置闪回数据库参数
设置数据库闪回的三个参数：
db_recovery_file_dest_size  闪回恢复区大小
db_recovery_file_dest  闪回恢复区路径，该参数可以任意指定，闪回日志记录了数据库的前影像，该日志不会进行归档，一但停用数据库的闪回功能，该目录下的日志会
自动清除
db_flashback_retention_target  保留恢复最近多长时间的数据，单位为分钟。
SQL> alter system set db_recovery_file_dest_size=5G;
System altered.
SQL> alter system set db_recovery_file_dest=‘/home/oracle/flash‘;
System altered.
SQL> alter system set db_flashback_retention_target=2440;  --分钟  2天，系统默认是1天
System altered.




回收站（recyclebin)：从管理的角度为每个用户“分配”一个回收站，但这个回收站并不实际开辟空间(逻辑容器），当drop table时（非purge），原来的表所使用的段中的数据并没有真正的删除。实际上是把table的段名以回收站方式重命名。该段所在表空间不足需要扩展时，回收站中的信息会被自动清除。


一：  


闪回一张无索引与约束的普通表


-- 查看是否有闪回功能  ON表示闪回已开  OFF表示闪回关闭
SQL> show parameter recyclebin


NAME                                 TYPE        VALUE
------------------------------------ ----------- ---------
recyclebin                           string      on


SQL> desc andy.andy;
 Name                                      Null?    Type
 ----------------------------------------- -------- --------------
 ID                                                 NUMBER(38)


SQL> drop table andy.andy;


Table dropped.


SQL> select * from andy.andy;
select * from andy.andy
                   *
ERROR at line 1:
ORA-00942: table or view does not exist


SQL> flashback table andy.andy to before drop;


Flashback complete.


SQL> select * from andy.andy;


        ID
----------
       100








二：


 闪回一张带索引与约束的表


1） 准备环境


SQL> 
create table school(sid number(4),sname varchar2(400 char), check_status number(1) default 0 check( check_status in(0,1)),accountant varchar2(20 char)unique,pwd varchar2(20 char),email varchar2(30 char),photo_path  varchar2(800 char),
constraint pk_t_school primary key(sid));


Table created.


SQL> insert into andy.school(sid,sname) values(1,‘andy‘);


1 row created.


SQL> insert into andy.school(sid,sname) values(2,‘andy‘);


1 row created.


SQL> col sname for a40
SQL> select sid,sname from andy.school;


       SID SNAME
---------- ----------------------------------------
         1 andy
         2 andy


-- 用andy用户登录
sqlplus andy/[email protected]:1521/orcl




2）查一下约束和索引


SQL> SELECT index_name, column_name, descend  FROM user_ind_columns  WHERE table_name = ‘SCHOOL‘;


INDEX_NAME                     COLUMN_NAME                              DESC
------------------------------ ---------------------------------------- ----
BIN$CgrA2XbJP/jgUGQKDRkLsQ==$0 SID                                      ASC
BIN$CgrA2XbKP/jgUGQKDRkLsQ==$0 ACCOUNTANT                               ASC


SQL> select CONSTRAINT_NAME,TABLE_NAME, COLUMN_NAME from user_cons_columns where TABLE_NAME=‘SCHOOL‘;


CONSTRAINT_NAME                TABLE_NAME                     COLUMN_NAME
------------------------------ ------------------------------ ----------------------------------------
BIN$CgrA2XbGP/jgUGQKDRkLsQ==$0 SCHOOL                         CHECK_STATUS
BIN$CgrA2XbHP/jgUGQKDRkLsQ==$0 SCHOOL                         SID
BIN$CgrA2XbIP/jgUGQKDRkLsQ==$0 SCHOOL                         ACCOUNTANT


3）表被drop到回收站，查一查约束和索引


SQL> drop table school;


Table dropped.


SQL> select INDEX_NAME,TABLE_NAME from user_indexes where table_name =‘SCHOOL‘;


no rows selected


SQL> select CONSTRAINT_NAME,TABLE_NAME from user_constraints where table_name=‘SCHOOL‘;


no rows selected


4）闪回表，查一查约束与索引


SQL> flashback table school to before drop;


Flashback complete.


SQL> SELECT index_name, column_name, descend  FROM user_ind_columns  WHERE table_name = ‘SCHOOL‘;


INDEX_NAME                     COLUMN_NAME                              DESC
------------------------------ ---------------------------------------- ----
BIN$CgrA2XbJP/jgUGQKDRkLsQ==$0 SID                                      ASC
BIN$CgrA2XbKP/jgUGQKDRkLsQ==$0 ACCOUNTANT                               ASC


SQL> select CONSTRAINT_NAME,TABLE_NAME, COLUMN_NAME from user_cons_columns where TABLE_NAME=‘SCHOOL‘;


CONSTRAINT_NAME                TABLE_NAME                     COLUMN_NAME
------------------------------ ------------------------------ ----------------------------------------
BIN$CgrA2XbGP/jgUGQKDRkLsQ==$0 SCHOOL                         CHECK_STATUS
BIN$CgrA2XbHP/jgUGQKDRkLsQ==$0 SCHOOL                         SID
BIN$CgrA2XbIP/jgUGQKDRkLsQ==$0 SCHOOL                         ACCOUNTANT


5）分别重命名索引和约束


SQL> alter index "BIN$CgrA2XbJP/jgUGQKDRkLsQ==$0" rename to PK_T_SCHOOL;


Index altered.


SQL> alter index "BIN$CgrA2XbKP/jgUGQKDRkLsQ==$0" rename to SYS_C0024861;


Index altered.


SQL> alter table school rename constraint "BIN$CgrA2XbGP/jgUGQKDRkLsQ==$0" to SYS_C0024859;


Table altered.


SQL> alter table school rename constraint "BIN$CgrA2XbHP/jgUGQKDRkLsQ==$0" to PK_T_SCHOOL ;


Table altered.


SQL> alter table school rename constraint "BIN$CgrA2XbIP/jgUGQKDRkLsQ==$0" to SYS_C0024861;


Table altered.


6）查看修改后的索引名与约束名
SQL> SELECT index_name, column_name, descend  FROM user_ind_columns  WHERE table_name = ‘SCHOOL‘;


INDEX_NAME                     COLUMN_NAME                              DESC
------------------------------ ---------------------------------------- ----
PK_T_SCHOOL                    SID                                      ASC
SYS_C0024861                   ACCOUNTANT                               ASC


SQL>  select CONSTRAINT_NAME,TABLE_NAME, COLUMN_NAME from user_cons_columns where TABLE_NAME=‘SCHOOL‘;


CONSTRAINT_NAME                TABLE_NAME                     COLUMN_NAME
------------------------------ ------------------------------ ----------------------------------------
SYS_C0024859                   SCHOOL                         CHECK_STATUS
PK_T_SCHOOL                    SCHOOL                         SID
SYS_C0024861                   SCHOOL                         ACCOUNTANT


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