CBA

Compress table 的内部存储细节研究

2019-09-11 11:46:22来源:励志吧0次阅读

SQL> create table test1(a varchar2(20),b varchar2(20),c varchar2(20)) compress;

SQL> select TABLESPACE_NAME ,EXTENT_ID ,blocks from dba_extents where segment_name = 'TEST1';

TABLESPACE_NAME         EXTENT_ID   BLOCKS

------------------------------ ---------- ----------

USERS                  0     8

SQL> select file_id,block_id from dba_extents where segment_name = 'TEST1';

FILE_ID  BLOCK_ID

---------- ----------

11    769

SQL> insert /*+ append */ into test1 select 'AAAAAAAAAAAAAAAAAAAA','BBBBBBBBBBBBBBBBBBBB','CCCCCCCCCCCCCCCCCCCC' from dba_objects where rownum < 1001;

1000 rows created.

SQL> commit;

Commit complete.

SQL> alter system dump datafile 11 block min 769 block max 771;

System altered.

trace 部分内容

data_block_dump,data header at 0xadb4674

===============

tsiz: 0x1f88

hsiz: 0x5ce

pbl: 0x0adb4674

bdba: 0x02c00302

76543210

flag=-0------

ntab=2

nrow=724

frre=-1

fsbo=0x5ce

fseo=0x1127

avsp=0xd

tosp=0xd

r0_9ir2=0x0

mec_kdbh9ir2=0x1

r1_9ir2=0x0

76543210

flag_9ir2=-------C

fcls_9ir2[4]={ 0 32768 32768 32768 }

0x1e: pti[0]   nrow=1 offs=0

0x22: pti[1]   nrow=723    offs=1

0x26: pri[0]   offs=0x1f46

0x28: pri[1]   offs=0x1f41

0x2a: pri[2]   offs=0x1f3c

0x2c: pri[3]   offs=0x1f37

x5b6: pri[712] offs=0x115e

0x5b8: pri[713] offs=0x1159

0x5ba: pri[714] offs=0x1154

0x5bc: pri[715] offs=0x114f

0x5be: pri[716] offs=0x114a

0x5c0: pri[717] offs=0x1145

0x5c2: pri[718] offs=0x1140

0x5c4: pri[719] offs=0x113b

0x5c6: pri[720] offs=0x1136

0x5c8: pri[721] offs=0x1131

0x5ca: pri[722] offs=0x112c

0x5cc: pri[723] offs=0x1127  总记录条数724条,每条消耗5字节存储

block_row_dump:

tab 0, row 0, @0x1f46

tl: 66 fb: --H-FL-- lb: 0x0 cc: 3

col 0: [20] 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41

col 1: [20] 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42

col 2: [20] 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43

bindmp: 02 d3 03 dc 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 dc 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 dc 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43

这部分为集中存储

tab 1, row 0, @0x1f41

tl: 5 fb: --H-FL-- lb: 0x0 cc: 3

col 0: [20] 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41

col 1: [20] 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42

col 2: [20] 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43

bindmp: 2c 00 01 03 00  这里的5个字节就是实际存储内容,03 表示压缩了3个字段,估计这里最后00表示指针指向第一个存储了完全数据的 ROW 0

tab 1, row 1, @0x1f3c

tl: 5 fb: --H-FL-- lb: 0x0 cc: 3

col 0: [20] 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41

col 1: [20] 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42

col 2: [20] 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43

bindmp: 2c 00 01 03 00

tab 1, row 2, @0x1f37

tl: 5 fb: --H-FL-- lb: 0x0 cc: 3

col 0: [20] 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41

col 1: [20] 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42

col 2: [20] 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43

bindmp: 2c 00 01 03 00

tab 1, row 3, @0x1f32

tl: 5 fb: --H-FL-- lb: 0x0 cc: 3

col 0: [20] 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41

col 1: [20] 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42

col 2: [20] 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43

bindmp: 2c 00 01 03 00

tab 1, row 4, @0x1f2d

tl: 5 fb: --H-FL-- lb: 0x0 cc: 3

col 0: [20] 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41

col 1: [20] 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42

col 2: [20] 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43

bindmp: 2c 00 01 03 00

tab 1, row 5, @0x1f28

tl: 5 fb: --H-FL-- lb: 0x0 cc: 3

col 0: [20] 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41

col 1: [20] 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42

col 2: [20] 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43

bindmp: 2c 00 01 03 00

tab 1, row 6, @0x1f23

SQL> truncate table test1;

Table truncated.

SQL> conn test/test

Connected.

SQL> insert /*+ append */ into test1 select rownum,'BBBBBBBBBBBBBBBBBBBB','CCCCCCCCCCCCCCCCCCCC' from dba_objects where rownum < 1001;

1000 rows created.

SQL> commit;

Commit complete.

SQL> alter system dump datafile 11 block min 769 block max 771;

System altered.

data_block_dump,data header at 0xadb4674

===============

tsiz: 0x1f88

hsiz: 0x5b2

pbl: 0x0adb4674

bdba: 0x02c00302

76543210

flag=-0------

ntab=2

nrow=709

frre=-1

fsbo=0x5b2

fseo=0x6e3

avsp=0xc5

tosp=0xc5

r0_9ir2=0x0

mec_kdbh9ir2=0x1

r1_9ir2=0x0

76543210

flag_9ir2=------OC

fcls_9ir2[3]={ 0 32768 32768 }

perm_9ir2[3]={ 2 0 1 } 这部分很关键,表示下面的实际存储字段顺序

也就是说,后面物理存储的顺序COL2,COL0,COL1对应数据字典中列的顺序应该是col0,col1,col2

0x20: pti[0]   nrow=1 offs=0

0x24: pti[1]   nrow=708    offs=1

0x28: pri[0]   offs=0x1f5b

0x2a: pri[1]   offs=0x1f54

0x2c: pri[2]   offs=0x1f4d

0x2e: pri[3]   offs=0x1f46

0x30: pri[4]   offs=0x1f3f

0x32: pri[5]   offs=0x1f38

0x34: pri[6]   offs=0x1f31

0x36: pri[7]   offs=0x1f2a

0x38: pri[8]   offs=0x1f23

x25c: pri[282] offs=0x1571

0x25e: pri[283] offs=0x1568

0x260: pri[284] offs=0x155f

0x262: pri[285] offs=0x1556

0x264: pri[286] offs=0x154d

0x266: pri[287] offs=0x1544

0x268: pri[288] offs=0x153b

0x26a: pri[289] offs=0x1532

0x26c: pri[290] offs=0x1529

0x26e: pri[291] offs=0x1520

0x270: pri[292] offs=0x1516

block_row_dump:

tab 0, row 0, @0x1f5b

tl: 45 fb: --H-FL-- lb: 0x0 cc: 2

col 0: [20] 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42

col 1: [20] 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43

bindmp: 01 24 02 dc 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 dc 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43

tab 1, row 0, @0x1f52

tl: 9 fb: --H-FL-- lb: 0x0 cc: 3

col 0: [20] 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42

col 1: [20] 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43 43

col 2: [ 3] 37 30 39

bindmp: 2c 00 02 02 00 cb 37 30 39  查看本文来源

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