重庆ORACLE 窥视索引内部结构-重庆科禄德科技有限公司

位图索引–反转索引

准备环境和测试数据

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Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit Production 
 
conn to pluggable database :
 
alter pluggable database testpdb open;
 
sqlplus zfy/zfy@serdb:1521/testpdb
 
SQL> show con_name;
 
CON_NAME
------------------------------
TESTPDB
 
SQL> sho user;
USER is "ZFY"
 
alter session set nls_date_format='yyyy-mm-dd hh24:mi:ss';

位图索引：

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create table tb_b (id number,name varchar2(100));
begin
for i in 1..10000
loop
insert into tb_b values(i,'a');
end loop;
end;
 
commit;
 
SQL> update tb_b set name='b' where id>5000;
 
create bitmap index idx_tb_b on tb_b(name);
 
exec sys.dbms_stats.gather_table_stats ( OwnName => 'ZFY',TabName => 'TB_B',Estimate_Percent => NULL,Method_Opt => 'FOR ALL COLUMNS SIZE 1 ',Cascade => True ,No_Invalidate => false);
 
col object_name for a12
select object_name,object_id from dba_objects where object_name in ('TB_B','IDX_TB_B');
 
OBJECT_NAME   OBJECT_ID
------------ ----------
IDX_TB_B         126042
TB_B             126041
 
select BLEVEL,LEAF_BLOCKS,DISTINCT_KEYS,AVG_LEAF_BLOCKS_PER_KEY,AVG_DATA_BLOCKS_PER_KEY,CLUSTERING_FACTOR from dba_indexes where index_name='IDX_TB_B';
 
    BLEVEL LEAF_BLOCKS DISTINCT_KEYS AVG_LEAF_BLOCKS_PER_KEY AVG_DATA_BLOCKS_PER_KEY CLUSTERING_FACTOR
---------- ----------- ------------- ----------------------- ----------------------- -----------------
         0           1             2                       1                       1                 2

注意这里的BLEVEL=0

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alter session set events 'immediate trace name treedump level 126042';
----- begin tree dump
*** 2018-03-03T00:29:56.446904+08:00 (TESTPDB(3))
leaf: 0x1818c0b 25267211 (0: row:2.2 avs:5775)
----- end tree dump
 
select to_number('18c0b','xxxxxxx') from dual;
 
SQL> alter system checkpoint;
 
System altered.
 
SQL> alter system dump datafile 13 block 101387;
 
System altered.

trace 信息：

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Block header dump:  0x01818c0b
 Object id on Block? Y
 seg/obj: 0x1ec5a  csc:  0x0000000002097235  itc: 2  flg: E  typ: 2 - INDEX
     brn: 0  bdba: 0x1818c08 ver: 0x01 opc: 0
     inc: 0  exflg: 0
 
 Itl           Xid                  Uba         Flag  Lck        Scn/Fsc
0x01   0x0000.000.00000000  0x00000000.0000.00  ----    0  fsc 0x0000.00000000
0x02   0x0001.00c.00000e8b  0x00c00c8a.0489.14  --U-    2  fsc 0x02d1.02097239
Leaf block dump
===============
header address 139977719369828=0x7f4f1a3d5064
kdxcolev 0
KDXCOLEV Flags = - - -
kdxcolok 0
kdxcoopc 0x80: opcode=0: iot flags=--- is converted=Y
kdxconco 4
kdxcosdc 0
kdxconro 2
kdxcofbo 40=0x28
kdxcofeo 642=0x282
kdxcoavs 5775
kdxlespl 0
kdxlende 0
kdxlenxt 0=0x0
kdxleprv 0=0x0
kdxledsz 0
kdxlebksz 8032
row#0[1410] flag: -----R-, lock: 2, len=747, rsl=721
col 0; len 1; (1):  61 ---a为61
col 1; len 6; (6):  00 00 00 00 00 00  --Z小rowid
col 2; len 6; (6):  01 81 8c 15 01 7f  --Z大rowid
col 3; len 727; (727): ---位图编码
 ff a1 ba be e0 08 ff ff ff ff ff ff ff ff cf ff ff ff ff ff ff ff ff cf ff
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 ca ff ff 0f ff dc 85 01 ff ff ff ff ff ff ff ff cf ff ff ff ff ff ff ff ff
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 ff 0f
row#1[642] flag: -------, lock: 2, len=749
col 0; len 1; (1):  62
col 1; len 6; (6):  00 00 00 00 00 00
col 2; len 6; (6):  01 81 8c 1e 00 67
col 3; len 729; (729): 
 ff a7 c4 bf e0 08 ff ff ff ff ff ff ff ff cf ff ff ff ff ff ff ff ff cf ff
 ff ff ff ff ff ff ff cf ff ff ff ff ff ff ff ff cf ff ff ff ff ff ff ff ff
 cf ff ff ff ff ff ff ff ff cf ff ff ff ff ff ff ff ff cf ff ff ff ff ff ff
 ff ff cf ff ff ff ff ff ff ff ff cf ff ff ff ff ff ff ff ff ca ff ff 0f ff
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 ff cf ff ff ff ff ff ff ff ff ca ff ff 0f ff 90 01 f0 ff ff ff ff ff ff ff
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 cf ff ff ff ff ff ff ff ff cf ff ff ff ff ff ff ff ff ca ff ff 0f ff f8 02
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 cf ff ff ff ff ff ff ff ff ca ff ff 0f ff 04 ff ff ff ff ff ff ff ff cc ff
 ff ff ff 0f
----- end of leaf block Logical dump -----
----- end of leaf block dump -----
End dump data blocks tsn: 6 file#: 13 minblk 101387 maxblk 101387