Oracle嵌套表存儲格式淺析

Oracle嵌套表存儲格式淺析

Oracle嵌套表很少用，下面來研究下其如何存儲的。用一個例子，一個用戶對應對個部門。

SQL> select * from v$version;
BANNER
--------------------------------------------------------------------------------
Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - 64bit Production
PL/SQL Release 11.2.0.1.0 - Production
CORE 11.2.0.1.0 Production
TNS for Linux: Version 11.2.0.1.0 - Production
NLSRTL Version 11.2.0.1.0 - Production

SQL> create type t_dept as object(

dept_id number,
dept_name varchar2(20)
)
/
SQL> create type t_dept_arry as varray(100) of t_dept
/
SQL> create table t_user(
user_id number,
user_name varchar2(10),
depts t_dept_arry
)
/
SQL> insert into t_user values(1,'張三',t_dept_arry(t_dept(100,'開發一組'),t_dept(200,'開發二組')));
SQL> insert into t_user values(2,'李四',t_dept_arry(t_dept(300,'設計一組'),t_dept(400,'設計二組')));

SQL> commit;

--要想遍歷用戶的所有部門信息，需要用table這種特殊的形式

SQL> select user_id,user_name,d.dept_id,d.dept_name from t_user u,table(u.depts) d;
USER_ID USER_NAME DEPT_ID DEPT_NAME
---------- ---------- ---------- --------------------
1 張三 100 開發一組
1 張三 200 開發二組
2 李四 300 設計一組
2 李四 400 設計二組
dump block看看：
block_row_dump:
tab 0, row 0, @0x3f47
tl: 81 fb: --H-FL-- lb: 0x1 cc: 3
col 0: [ 2] c1 02
col 1: [ 4] d5 c5 c8 fd
col 2: [69]
00 01 00 00 00 00 00 01 00 00 00 0a e4 23 00 37 09 00 00 00 00 00 00 27 00
00 00 00 00 01 88 01 27 01 01 00 02 0f 84 01 0f 02 c2 02 08 bf aa b7 a2 d2
bb d7 e9 0f 84 01 0f 02 c2 03 08 bf aa b7 a2 b6 fe d7 e9
tab 0, row 1, @0x3ef6
tl: 81 fb: --H-FL-- lb: 0x1 cc: 3
col 0: [ 2] c1 03
col 1: [ 4] c0 ee cb c4
col 2: [69]
00 01 00 00 00 00 00 01 00 00 00 0a e4 24 00 37 09 00 00 00 00 00 00 27 00
00 00 00 00 01 88 01 27 01 01 00 02 0f 84 01 0f 02 c2 04 08 c9 e8 bc c6 d2
bb d7 e9 0f 84 01 0f 02 c2 05 08 c9 e8 bc c6 b6 fe d7 e9
end_of_block_dump

insert into t_user values(3,'王五',t_dept_arry(t_dept(500,'家')));
commit;

block_row_dump:
tab 0, row 0, @0x3f5d
tl: 59 fb: --H-FL-- lb: 0x1 cc: 3
col 0: [ 2] c1 04
col 1: [ 4] cd f5 ce e5
col 2: [47]
00 01 00 00 00 00 00 01 00 00 00 0a e4 49 00 21 09 00 00 00 00 00 00 11 00
00 00 00 00 01 88 01 11 01 01 00 01 09 84 01 09 02 c2 06 02 bc d2
end_of_block_dump
--看了上面dump的結果，一頭霧水，不知道是怎麼存的，不過在user_objects中找到線索，有個lob字段
SQL> select object_name,object_type from user_objects s;
OBJECT_NAME OBJECT_TYPE
------------------------------ -------------------
SYS_LOB0000082685C00003$$ LOB
T_USER TABLE
T_DEPT_ARRY TYPE
T_DEPT TYPE

SQL> select column_name, segment_name, index_name
from user_lobs s
where s.table_name = 'T_USER';
COLUMN_NAM SEGMENT_NAME INDEX_NAME
---------- ------------------------------ ------------------------------

DEPTS SYS_LOB0000082685C00003$$ SYS_IL0000082685C00003$$

--再測試下跟普通的clob有什麼區別

drop table test purge;
create table test
(
id number,
t_clob clob
);
insert into test values(1,'開發一組開發二組');
insert into test values(1,'設計一組設計二組');
insert into test values(1,'家');

commit;

tab 0, row 0, @0x3f5d
tl: 59 fb: --H-FL-- lb: 0x1 cc: 2
col 0: [ 2] c1 02
col 1: [52]
00 54 00 01 02 0c 80 00 00 02 00 00 00 01 00 00 00 0a e4 4a 00 20 09 00 00
00 00 00 00 10 00 00 00 00 00 01 5f 00 53 d1 4e 00 7e c4 5f 00 53 d1 4e 8c
7e c4
LOB
Locator:
Length: 84(52)
Version: 1
Byte Length: 2
LobID: 00.00.00.01.00.00.00.0a.e4.4a
Flags[ 0x02 0x0c 0x80 0x00 ]:
Type: CLOB
Storage: BasicFile
Enable Storage in Row
Characterset Format: IMPLICIT
Partitioned Table: No
Options: VaringWidthReadWrite
Inode:
Size: 32
Flag: 0x09 [ Valid DataInRow ]
Future: 0x00 (should be '0x00')
Blocks: 0
Bytes: 16
Version: 00000.0000000001
Inline data[16]
Dump of memory from 0x00002AE680C155EC to 0x00002AE680C155FC
2AE680C155E0 D153005F [_.S.]
2AE680C155F0 C47E004E D153005F C47E8C4E [N.~._.S.N.~.]
tab 0, row 1, @0x3f22
tl: 59 fb: --H-FL-- lb: 0x1 cc: 2
col 0: [ 2] c1 02
col 1: [52]
00 54 00 01 02 0c 80 00 00 02 00 00 00 01 00 00 00 0a e4 4b 00 20 09 00 00
00 00 00 00 10 00 00 00 00 00 01 8b be 8b a1 4e 00 7e c4 8b be 8b a1 4e 8c
7e c4
LOB
Locator:
Length: 84(52)
Version: 1
Byte Length: 2
LobID: 00.00.00.01.00.00.00.0a.e4.4b
Flags[ 0x02 0x0c 0x80 0x00 ]:
Type: CLOB
Storage: BasicFile
Enable Storage in Row
Characterset Format: IMPLICIT
Partitioned Table: No
Options: VaringWidthReadWrite
Inode:
Size: 32
Flag: 0x09 [ Valid DataInRow ]
Future: 0x00 (should be '0x00')
Blocks: 0
Bytes: 16
Version: 00000.0000000001
Inline data[16]
Dump of memory from 0x00002AE680C155B1 to 0x00002AE680C155C1
2AE680C155B0 8BBE8B01 7E004EA1 8BBE8BC4 7E8C4EA1 [.....N.~.....N.~]
2AE680C155C0 02012CC4 [.,..]
tab 0, row 2, @0x3ef5
tl: 45 fb: --H-FL-- lb: 0x1 cc: 2
col 0: [ 2] c1 02
col 1: [38]
00 54 00 01 02 0c 80 00 00 02 00 00 00 01 00 00 00 0a e4 4c 00 12 09 00 00
00 00 00 00 02 00 00 00 00 00 01 5b b6
LOB
Locator:
Length: 84(38)
Version: 1
Byte Length: 2
LobID: 00.00.00.01.00.00.00.0a.e4.4c
Flags[ 0x02 0x0c 0x80 0x00 ]:
Type: CLOB
Storage: BasicFile
Enable Storage in Row
Characterset Format: IMPLICIT
Partitioned Table: No
Options: VaringWidthReadWrite
Inode:
Size: 18
Flag: 0x09 [ Valid DataInRow ]
Future: 0x00 (should be '0x00')
Blocks: 0
Bytes: 2
Version: 00000.0000000001
Inline data[2]

選取兩次的dump的內容，不過還是不能確定兩者是否等價：

00 01 00 00 00 00 00 01 00 00 00 0a e4 49 00 21 09 00 00 00 00 00 00 11 00
00 00 00 00 01 88 01 11 01 01 00 01 09 84 01 09 02 c2 06 02 bc d2

00 54 00 01 02 0c 80 00 00 02 00 00 00 01 00 00 00 0a e4 4c 00 12 09 00 00
00 00 00 00 02 00 00 00 00 00 01 5b b6

總結：嵌套是通過lob在存儲嵌套的內容的，TOM說作為一種存儲機制，他更傾向於創建父子表，可以再創建一個視圖，看上去像一個真正的嵌套表一樣，嵌套表適合於編程構造。