Oracle 局部前缀索引和局部非前缀索引
2016-01-04 11:24
477 查看
局部前缀索引和局部非前缀索引是对于分区表而言的，那到底选择哪种索引呢？先做一个实验：
1.制造数据
create table TEST_P
(
OWNER VARCHAR2(30),
OBJECT_NAME VARCHAR2(128),
SUBOBJECT_NAME VARCHAR2(30),
OBJECT_ID NUMBER,
DATA_OBJECT_ID NUMBER,
OBJECT_TYPE VARCHAR2(19),
CREATED DATE,
LAST_DDL_TIME DATE,
TIMESTAMP VARCHAR2(19),
STATUS VARCHAR2(7),
TEMPORARY VARCHAR2(1),
GENERATED VARCHAR2(1),
SECONDARY VARCHAR2(1),
NAMESPACE NUMBER,
EDITION_NAME VARCHAR2(30)
)partition by list(owner)(
partition p1 values('SYS'),
partition p2 values('PUBLIC'),
partition p3 values('SYSMAN'),
partition p4 values('APEX_030200'),
partition p5 values('ORDSYS'),
partition p6 values('MDSYS'),
partition p7 values('XDB'),
partition p8 values('OLAPSYS'),
partition p9 values('SYSTEM'),
partition p_default values(DEFAULT)
);
insert into TEST_P select * from dba_objects;
commit;
2.局部前缀索引(local nonprefixed index)
create index ind_local_prfixed on TEST_P(owner,object_id) local nologging;
exec dbms_stats.gather_table_stats(user,'TEST_P',cascade => true);
SQL> set autotrace traceonly
SQL> select * from TEST_P where object_id = 4903;
执行计划
----------------------------------------------------------
Plan hash value: 3793878917
------------------------------------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | Pstart| Pstop |
------------------------------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 97 | 28 (0)| 00:00:01 | | |
| 1 | PARTITION LIST ALL | | 1 | 97 | 28 (0)| 00:00:01 | 1 | 10 |
| 2 | TABLE ACCESS BY LOCAL INDEX ROWID| TEST_P | 1 | 97 | 28 (0)| 00:00:01 | 1 | 10 |
|* 3 | INDEX SKIP SCAN | IND_LOCAL_PRFIXED | 1 | | 27 (0)| 00:00:01 | 1 | 10 |
------------------------------------------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
3 - access("OBJECT_ID"=4903)
filter("OBJECT_ID"=4903)
统计信息
----------------------------------------------------------
1 recursive calls
0 db block gets
38 consistent gets
0 physical reads
0 redo size
1294 bytes sent via SQL*Net to client
472 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
1 rows processed
SQL> select * from TEST_P where object_id = 4903 and owner='SYS';
执行计划
----------------------------------------------------------
Plan hash value: 1414917495
------------------------------------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | Pstart| Pstop |
------------------------------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 96 | 2 (0)| 00:00:01 | | |
| 1 | PARTITION LIST SINGLE | | 1 | 96 | 2 (0)| 00:00:01 | KEY | KEY |
| 2 | TABLE ACCESS BY LOCAL INDEX ROWID| TEST_P | 1 | 96 | 2 (0)| 00:00:01 | 1 | 1 |
|* 3 | INDEX RANGE SCAN | IND_LOCAL_PRFIXED | 1 | | 1 (0)| 00:00:01 | 1 | 1 |
------------------------------------------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
3 - access("OWNER"='SYS' AND "OBJECT_ID"=4903)
统计信息
----------------------------------------------------------
1 recursive calls
0 db block gets
4 consistent gets
0 physical reads
0 redo size
1294 bytes sent via SQL*Net to client
472 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
1 rows processed
SQL> drop index ind_local_prfixed;
3.局部非前缀索引(local nonprefixed index)
SQL> create index ind_local_nonprfixed on TEST_P(object_id) local nologging;
SQL> select * from TEST_P where object_id = 4903;
执行计划
----------------------------------------------------------
Plan hash value: 449164761
---------------------------------------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | Pstart| Pstop |
---------------------------------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 97 | 12 (0)| 00:00:01 | | |
| 1 | PARTITION LIST ALL | | 1 | 97 | 12 (0)| 00:00:01 | 1 | 10 |
| 2 | TABLE ACCESS BY LOCAL INDEX ROWID| TEST_P | 1 | 97 | 12 (0)| 00:00:01 | 1 | 10 |
|* 3 | INDEX RANGE SCAN | IND_LOCAL_NONPRFIXED | 1 | | 11 (0)| 00:00:01 | 1 | 10 |
---------------------------------------------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
3 - access("OBJECT_ID"=4903)
统计信息
----------------------------------------------------------
1 recursive calls
0 db block gets
22 consistent gets
44 physical reads
0 redo size
1294 bytes sent via SQL*Net to client
472 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
1 rows processed
SQL> select * from TEST_P where object_id = 4903 and owner='SYS';
执行计划
----------------------------------------------------------
Plan hash value: 747180801
---------------------------------------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | Pstart| Pstop |
---------------------------------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 96 | 2 (0)| 00:00:01 | | |
| 1 | PARTITION LIST SINGLE | | 1 | 96 | 2 (0)| 00:00:01 | KEY | KEY |
| 2 | TABLE ACCESS BY LOCAL INDEX ROWID| TEST_P | 1 | 96 | 2 (0)| 00:00:01 | 1 | 1 |
|* 3 | INDEX RANGE SCAN | IND_LOCAL_NONPRFIXED | 1 | | 1 (0)| 00:00:01 | 1 | 1 |
---------------------------------------------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
3 - access("OBJECT_ID"=4903)
统计信息
----------------------------------------------------------
1 recursive calls
0 db block gets
4 consistent gets
0 physical reads
0 redo size
1294 bytes sent via SQL*Net to client
472 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
1 rows processed
结论：从实验来看，不管是使用哪种索引，SQL条件中都要使用分区条件，要不然两种索引都要全分区扫描。加了分区条件后，两种索引都可以消除分区，所以我建议还是用局部非前缀索引。
1.制造数据
create table TEST_P
(
OWNER VARCHAR2(30),
OBJECT_NAME VARCHAR2(128),
SUBOBJECT_NAME VARCHAR2(30),
OBJECT_ID NUMBER,
DATA_OBJECT_ID NUMBER,
OBJECT_TYPE VARCHAR2(19),
CREATED DATE,
LAST_DDL_TIME DATE,
TIMESTAMP VARCHAR2(19),
STATUS VARCHAR2(7),
TEMPORARY VARCHAR2(1),
GENERATED VARCHAR2(1),
SECONDARY VARCHAR2(1),
NAMESPACE NUMBER,
EDITION_NAME VARCHAR2(30)
)partition by list(owner)(
partition p1 values('SYS'),
partition p2 values('PUBLIC'),
partition p3 values('SYSMAN'),
partition p4 values('APEX_030200'),
partition p5 values('ORDSYS'),
partition p6 values('MDSYS'),
partition p7 values('XDB'),
partition p8 values('OLAPSYS'),
partition p9 values('SYSTEM'),
partition p_default values(DEFAULT)
);
insert into TEST_P select * from dba_objects;
commit;
2.局部前缀索引(local nonprefixed index)
create index ind_local_prfixed on TEST_P(owner,object_id) local nologging;
exec dbms_stats.gather_table_stats(user,'TEST_P',cascade => true);
SQL> set autotrace traceonly
SQL> select * from TEST_P where object_id = 4903;
执行计划
----------------------------------------------------------
Plan hash value: 3793878917
------------------------------------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | Pstart| Pstop |
------------------------------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 97 | 28 (0)| 00:00:01 | | |
| 1 | PARTITION LIST ALL | | 1 | 97 | 28 (0)| 00:00:01 | 1 | 10 |
| 2 | TABLE ACCESS BY LOCAL INDEX ROWID| TEST_P | 1 | 97 | 28 (0)| 00:00:01 | 1 | 10 |
|* 3 | INDEX SKIP SCAN | IND_LOCAL_PRFIXED | 1 | | 27 (0)| 00:00:01 | 1 | 10 |
------------------------------------------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
3 - access("OBJECT_ID"=4903)
filter("OBJECT_ID"=4903)
统计信息
----------------------------------------------------------
1 recursive calls
0 db block gets
38 consistent gets
0 physical reads
0 redo size
1294 bytes sent via SQL*Net to client
472 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
1 rows processed
SQL> select * from TEST_P where object_id = 4903 and owner='SYS';
执行计划
----------------------------------------------------------
Plan hash value: 1414917495
------------------------------------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | Pstart| Pstop |
------------------------------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 96 | 2 (0)| 00:00:01 | | |
| 1 | PARTITION LIST SINGLE | | 1 | 96 | 2 (0)| 00:00:01 | KEY | KEY |
| 2 | TABLE ACCESS BY LOCAL INDEX ROWID| TEST_P | 1 | 96 | 2 (0)| 00:00:01 | 1 | 1 |
|* 3 | INDEX RANGE SCAN | IND_LOCAL_PRFIXED | 1 | | 1 (0)| 00:00:01 | 1 | 1 |
------------------------------------------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
3 - access("OWNER"='SYS' AND "OBJECT_ID"=4903)
统计信息
----------------------------------------------------------
1 recursive calls
0 db block gets
4 consistent gets
0 physical reads
0 redo size
1294 bytes sent via SQL*Net to client
472 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
1 rows processed
SQL> drop index ind_local_prfixed;
3.局部非前缀索引(local nonprefixed index)
SQL> create index ind_local_nonprfixed on TEST_P(object_id) local nologging;
SQL> select * from TEST_P where object_id = 4903;
执行计划
----------------------------------------------------------
Plan hash value: 449164761
---------------------------------------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | Pstart| Pstop |
---------------------------------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 97 | 12 (0)| 00:00:01 | | |
| 1 | PARTITION LIST ALL | | 1 | 97 | 12 (0)| 00:00:01 | 1 | 10 |
| 2 | TABLE ACCESS BY LOCAL INDEX ROWID| TEST_P | 1 | 97 | 12 (0)| 00:00:01 | 1 | 10 |
|* 3 | INDEX RANGE SCAN | IND_LOCAL_NONPRFIXED | 1 | | 11 (0)| 00:00:01 | 1 | 10 |
---------------------------------------------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
3 - access("OBJECT_ID"=4903)
统计信息
----------------------------------------------------------
1 recursive calls
0 db block gets
22 consistent gets
44 physical reads
0 redo size
1294 bytes sent via SQL*Net to client
472 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
1 rows processed
SQL> select * from TEST_P where object_id = 4903 and owner='SYS';
执行计划
----------------------------------------------------------
Plan hash value: 747180801
---------------------------------------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | Pstart| Pstop |
---------------------------------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 96 | 2 (0)| 00:00:01 | | |
| 1 | PARTITION LIST SINGLE | | 1 | 96 | 2 (0)| 00:00:01 | KEY | KEY |
| 2 | TABLE ACCESS BY LOCAL INDEX ROWID| TEST_P | 1 | 96 | 2 (0)| 00:00:01 | 1 | 1 |
|* 3 | INDEX RANGE SCAN | IND_LOCAL_NONPRFIXED | 1 | | 1 (0)| 00:00:01 | 1 | 1 |
---------------------------------------------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
3 - access("OBJECT_ID"=4903)
统计信息
----------------------------------------------------------
1 recursive calls
0 db block gets
4 consistent gets
0 physical reads
0 redo size
1294 bytes sent via SQL*Net to client
472 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
1 rows processed
结论：从实验来看，不管是使用哪种索引，SQL条件中都要使用分区条件，要不然两种索引都要全分区扫描。加了分区条件后，两种索引都可以消除分区，所以我建议还是用局部非前缀索引。
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