Oracle11g温习-第十三章：索引

2013年4月27日星期六

10:46

1、索引（Index）的功能：对记录进行排序，加快表的查询速度

2、索引的分类

1）B-tree 索引（默认）

a、在一个大表上

b、建立在重复值比较少的列上，在做select查询时，返回记录的行数小于全部记录的4%

c、如果这一列经常用来做where子句和排序，也可以用来建立索引

d、一般用于OLTP

2） bitmap index

a、建立在重复值非常高的列上

b、在做DML 操作时，代价值比较高

c、一般用于OLAP 或DSS

—— B-tree 索引不能使用or连接的语句，bitmap index可以使用

3、建立索引：默认建立 B-tree index

4、建立索引表空间

SYS @ prod >create tablespace indexes datafile '/u01/app/oracle/oradata/prod/index01.dbf' size 50m autoextend on next 10m maxsize 50m extent management local uniform size 128k;

Tablespace created.

SQL> select file_id,file_name,tablespace_name from dba_data_files;

FILE_ID FILE_NAME TABLESPACE_NAME

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

1 /u01/app/oracle/oradata/prod/system01.dbf SYSTEM

2 /u01/app/oracle/oradata/prod/lx01.dbf LX01

3 /u01/app/oracle/oradata/prod/sysaux01.dbf SYSAUX

4 /u01/app/oracle/oradata/prod/users01.dbf USERS

7 /u01/app/oracle/oradata/prod/undotbs02.dbf UNDOTBS2

12 /u01/app/oracle/oradata/prod/index01.dbf INDEXES

SQL> create table test (id int,name varchar2(10),sex varchar2(4));

Table created.

SQL> begin

for i in 1..10000 loop

insert into test values(i,'user’||i,'M');

end loop;

end;

SQL> begin

for i in 10001..20000 loop

insert into test values(i,'user’||i,'F');

end loop;

end;

SQL> select count(*) from test;

COUNT(*)

----------

20000

——建立b-tree 索引

SQL> create index test_sex_idx on test(sex) tablespace indexes;

Index created.

——分析索引结构

SQL> analyze index test_sex_idx validate structure;

Index analyzed.

SQL> select index_name,index_type,tablespace_name,blevel,leaf_blocks,num_rows

from user_indexes where index_name='TEST_SEX_IDX';

INDEX_NAME INDEX_TYPE TABLESPACE_NAME BLEVEL LEAF_BLOCKS NUM_ROWS

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

TEST_SEX_IDX NORMAL INDEXES 1 37 20000

【——BLEVEL 索引的深度（高度 =深度+1）

——LEAF_BLOCKS，使用的索引块】

SQL> select index_name,table_name,column_name from user_ind_columns

where index_name='TEST_SEX_IDX';

INDEX_NAME TABLE_NAME COLUMN_NAME

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

TEST_SEX_IDX TEST SEX

SQL> select /*+ index (test TEST_SEX_IXD)*/ name,sex from test where sex='F';

10000 rows selected.

Execution Plan

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

Plan hash value: 1357081020

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

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

| 0 | SELECT STATEMENT | | 10000 | 97K| 15 (0)| 00:00:01 |

|* 1 | TABLE ACCESS FULL| TEST | 10000 | 97K| 15 (0)| 00:00:01 |

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

Predicate Information (identified by operation id):

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

1 - filter("SEX"='F')

Statistics

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

0 recursive calls

0 db block gets

0 consistent gets

0 physical reads

0 redo size

0 bytes sent via SQL*Net to client

0 bytes received via SQL*Net from client

0 SQL*Net roundtrips to/from client

0 sorts (memory)

0 sorts (disk)

10000 rows processed

SQL> drop index test_sex_idx;

Index dropped.

——建立位图索引

SQL> create bitmap index test_sex_bitind on test(sex) tablespace indexes;

Index created.

——分析索引结构

SQL> analyze index test_sex_bitind validate structure;

Index analyzed.

SQL> select index_name,index_type,tablespace_name,blevel,leaf_blocks,num_rows from user_indexes where index_name='TEST_SEX_BITIND';

INDEX_NAME INDEX_TYPE TABLESPACE_NAME BLEVEL LEAF_BLOCKS NUM_ROWS

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

TEST_SEX_BITIND BITMAP INDEXES 0 1 2

——在重复值高的列上适合建立bitmap的索引

SQL> select index_name,table_name,column_name from user_ind_columns

where index_name='TEST_SEX_BITIND';

INDEX_NAME TABLE_NAME COLUMN_NAME

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

TEST_SEX_BITIND TEST SEX

SQL> select /*+ index (test TEST_SEX_BITIND)*/ name,sex from test where sex='F';

10000 rows selected.

Execution Plan

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

Plan hash value: 2624764158

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

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

| 0 | SELECT STATEMENT | | 10000 | 97K| 85 (0)| 00:00:02 |

| 1 | TABLE ACCESS BY INDEX ROWID | TEST | 10000 | 97K| 85 (0)| 00:00:02 |

| 2 | BITMAP CONVERSION TO ROWIDS| | | | | |

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

Predicate Information (identified by operation id):

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

3 - access("SEX"='F')

Statistics

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

0 recursive calls

0 db block gets

0 consistent gets

0 physical reads

0 redo size

0 bytes sent via SQL*Net to client

0 bytes received via SQL*Net from client

0 SQL*Net roundtrips to/from client

0 sorts (memory)

0 sorts (disk)

10000 rows processed

SQL> drop index TEST_SEX_BITIND;

Index dropped.

5、基于函数的索引

SQL> conn scott/tiger

Connected.

SQL> set autotrace on;

SQL> create index emp_ename_ind on emp(ename) tablespace indexes;

Index created.

SQL> select * from emp where ename='SCOTT';

EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO

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

7788 SCOTT ANALYST 7566 1987-04-19 00:00:00 3000 20

Execution Plan

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

Plan hash value: 3220259315

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

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

| 0 | SELECT STATEMENT | | 1 | 87 | 2 (0)| 00:00:01 |

| 1 | TABLE ACCESS BY INDEX ROWID| EMP | 1 | 87 | 2 (0)| 00:00:01 |

|* 2 | INDEX RANGE SCAN | EMP_ENAME_IND | 1 | | 1 (0)| 00:00:01 |

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

Predicate Information (identified by operation id):

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

2 - access("ENAME"='SCOTT')

Note

-----

- dynamic sampling used for this statement

Statistics

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

0 recursive calls

0 db block gets

0 consistent gets

0 physical reads

0 redo size

0 bytes sent via SQL*Net to client

0 bytes received via SQL*Net from client

0 SQL*Net roundtrips to/from client

0 sorts (memory)

0 sorts (disk)

1 rows processed

——通过函数访问，索引无效

SQL> select * from emp where lower(ename)='scott';

EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO

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

7788 SCOTT ANALYST 7566 1987-04-19 00:00:00 3000 20

Execution Plan

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

Plan hash value: 3956160932

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

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

| 0 | SELECT STATEMENT | | 1 | 87 | 15 (0)| 00:00:01 |

|* 1 | TABLE ACCESS FULL| EMP | 1 | 87 | 15 (0)| 00:00:01 | ——索引无效

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

Predicate Information (identified by operation id):

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

1 - filter(LOWER("ENAME")='scott')

Note

-----

- dynamic sampling used for this statement

Statistics

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

0 recursive calls

0 db block gets

0 consistent gets

0 physical reads

0 redo size

0 bytes sent via SQL*Net to client

0 bytes received via SQL*Net from client

0 SQL*Net roundtrips to/from client

0 sorts (memory)

0 sorts (disk)

1 rows processed

——建立函数索引

SQL> create index emp_ename_funind on emp(lower(ename)) tablespace indexes;

Index created.

SQL> select * from emp where lower(ename)='scott';

EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO

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

7788 SCOTT ANALYST 7566 1987-04-19 00:00:00 3000 20

Execution Plan

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

Plan hash value: 519807088

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

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

| 0 | SELECT STATEMENT | | 1 | 87 | 2 (0)| 00:00:01 |

| 1 | TABLE ACCESS BY INDEX ROWID| EMP | 1 | 87 | 2 (0)| 00:00:01 |

|* 2 | INDEX RANGE SCAN | EMP_ENAME_FUNIND | 1 | | 1 (0)| 00:00:01 |

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

Predicate Information (identified by operation id):

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

2 - access(LOWER("ENAME")='scott')

Note

-----

- dynamic sampling used for this statement

Statistics

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

0 recursive calls

0 db block gets

0 consistent gets

0 physical reads

0 redo size

0 bytes sent via SQL*Net to client

0 bytes received via SQL*Net from client

0 SQL*Net roundtrips to/from client

0 sorts (memory)

0 sorts (disk)

1 rows processed

6、索引监控

SQL> conn scott/tiger

Connected.

SQL> alter index emp_ename_funind monitoring usage;

Index altered.

SQL> select index_name,table_name,monitoring,used from v$object_usage;

INDEX_NAME TABLE_NAME MONITORIN USED

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

EMP_ENAME_FUNIND EMP YES NO

SQL> select * from emp where LOWER(ename)='scott';

EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO

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

7788 SCOTT ANALYST 7566 19-APR-87 3000 20

SQL> select * from emp where lower(ename)='scott';

EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO

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

7788 SCOTT ANALYST 7566 1987-04-19 00:00:00 3000 20

SQL> select index_name,table_name,monitoring,used from v$object_usage;

INDEX_NAME TABLE_NAME MONITORIN USED

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

EMP_ENAME_FUNIND EMP YES YES

7、【反向索引----------用于建立索引的列值是连续的或通过序列生成时，避免索引存放到集中的leaf block上,避免生成热块】。

1）建立反向索引

SQL> create index r_empno_ind on test(empno) reverse;

Index created.

——【对于emp表里empno列来说，因为客户ID号顺序递增，所以为了均衡索引数据分布，应在该列上建立反向索引。】

2）重建索引

SQL> alter index r_empno_ind rebuild reverse;

Index altered.

8、与索引有关的视图

DBA_INDEXES:

DBA_IND_COLUMNS:

V$OBJECT_USAGE:

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原文地址：https://www.cnblogs.com/iyoume2008/p/7526340.html