定行
下面看下执行计划：
SQL> select * from dba_recyclebin;
执行计划
----------------------------------------------------------
Plan hash value: 1935272164
--------------------------------------------------------------------------------
--------------
| Id | Operation | Name | Rows | Bytes | Cost (%CP
U)| Time |
--------------------------------------------------------------------------------
--------------
| 0 | SELECT STATEMENT | | 2 | 336 | 12 (
9)| 00:00:01 |
|* 1 | FILTER | | | |
| |
|* 2 | HASH JOIN | | 2 | 336 | 12 (
9)| 00:00:01 |
| 3 | NESTED LOOPS | | | |
| |
| 4 | NESTED LOOPS | | 2 | 292 | 10 (
0)| 00:00:01 |
| 5 | NESTED LOOPS | | 2 | 202 | 6 (
0)| 00:00:01 |
| 6 | NESTED LOOPS OUTER | | 2 | 168 | 4 (
0)| 00:00:01 |
| 7 | TABLE ACCESS FULL | RECYCLEBIN$ | 2 | 146 | 2 (
0)| 00:00:01 |
| 8 | TABLE ACCESS CLUSTER | TS$ | 1 | 11 | 1 (
0)| 00:00:01 |
|* 9 | INDEX UNIQUE SCAN | I_TS# | 1 | | 0 (
0)| 00:00:01 |
| 10 | TABLE ACCESS CLUSTER | USER$ | 1 | 17 | 1 (
0)| 00:00:01 |
|* 11 | INDEX UNIQUE SCAN | I_USER# | 1 | | 0 (
0)| 00:00:01 |
|* 12 | INDEX RANGE SCAN | I_OBJ1 | 1 | | 1 (
0)| 00:00:01 |
| 13 | TABLE ACCESS BY INDEX ROWID| OBJ$ | 1 | 45 | 2 (
0)| 00:00:01 |
| 14 | INDEX FULL SCAN | I_USER2 | 97 | 2134 | 1 (
0)| 00:00:01 |
| 15 | NESTED LOOPS | | 1 | 29 | 2 (
0)| 00:00:01 |
|* 16 | INDEX FULL SCAN | I_USER2 | 1 | 20 | 1 (
0)| 00:00:01 |
|* 17 | INDEX RANGE SCAN | I_OBJ4 | 1 | 9 | 1 (
0)| 00:00:01 |
--------------------------------------------------------------------------------
--------------
下面摘自？/rdbms/admin/dsqlddl.bsq
create table recyclebin$
(
obj# number not null, /* original object number */
owner# number not null, /* owner user number */
original_name varchar2(32), /* Original Object Name */
operation number not null, /* Operation carried out */
/* 0 -> DROP */
/* 1 -> TRUNCATE (not supported) */
type# number not null, /* object type (see KQD.H) */
ts# number, /* tablespace number */
file# number, /* segment header file number */
block# number, /* segment header block number */
droptime date, /* time when object was dropped */
dropscn number, /* SCN of Tx which caused the drop */
partition_name varchar2(32), /* Name of the partition dropped */
/* NULL otherwise */
flags number, /* flags for undrop processing */
related number not null, /* obj one level up in heirarchy */
bo number not null, /* base object */
purgeobj number not null, /* obj to purge when purging this */
base_ts# number, /* Base objects Tablespace number */
base_owner# number, /* Base objects owner number */
space number, /* number of blocks used by the object */
con# number, /* con#, if index is due to constraint */
spare1 number,
spare2 number,
spare3 number
)
/
create index recyclebin$_obj on recyclebin$(obj#)
/
create index recyclebin$_ts on recyclebin$(ts#)
/
create index recyclebin$_owner on recyclebin$(owner#)
/
上面是数据字典recyclebin$的创建和注释，不断的深入，会更加清楚的认知。
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