Oracle?????輰????м??
???????????? ???????[ 2013/6/6 9:58:14 ] ????????
????4????????????Ч??
--?????????????
a????????????????
scott@ORA11G> @idx_info
Enter value for owner: scott
Enter value for table_name: big_table
Table Name Index Name CL_NAM CL_POS Status IDX_TYP DSCD
------------------------- ------------------------- --------- ------ -------- --------------- ----
BIG_TABLE BIG_TABLE_PK ID 1 VALID NORMAL ASC
scott@ORA11G> @idx_stat
Enter value for input_table_name: big_table
Enter value for owner: scott
AVG LEAF BLKS AVG DATA BLKS
BLEV IDX_NAME LEAF_BLKS DST_KEYS PER KEY PER KEY CLUST_FACT LAST_ANALYZED TB_BLKS TB_ROWS
---- -------------- ---------- ---------- ------------- ------------- ---------- ------------------ ---------- ----------
1 BIG_TABLE_PK 208 100000 1 1 1483 20130524 10:45:51 1515 100000
--????????????
scott@ORA11G> show parameter optimizer_index_
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
optimizer_index_caching integer 0
optimizer_index_cost_adj integer 100
scott@ORA11G> show parameter optimizer_mode
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
optimizer_mode string ALL_ROWS
b?????????20%?????е?????
scott@ORA11G> alter system flush buffer_cache;
scott@ORA11G> select sum(object_id)??avg(object_id) from big_table where id between 20000 and 40000;
Execution Plan
----------------------------------------------------------
Plan hash value: 3098837282 -- ??м???У????????????Χ???
---------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
---------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 18 | 341 (0)| 00:00:05 |
| 1 | SORT AGGREGATE | | 1 | 18 | | |
| 2 | TABLE ACCESS BY INDEX ROWID| BIG_TABLE | 20046 | 352K| 341 (0)| 00:00:05 |
|* 3 | INDEX RANGE SCAN | BIG_TABLE_PK | 20046 | | 43 (0)| 00:00:01 |
---------------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
3 - access("ID">=20000 AND "ID"<=40000)
Statistics
----------------------------------------------------------
0 recursive calls
0 db block gets
351 consistent gets
351 physical reads
0 redo size
427 bytes sent via SQL*Net to client
349 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
1 rows processed
scott@ORA11G> alter system flush buffer_cache;
scott@ORA11G> select /*+ full(big_table) */ sum(object_id)??avg(object_id) from big_table where id between 20000 and 40000;
Execution Plan
----------------------------------------------------------
Plan hash value: 599409829 ---- ??????????????????
--------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
--------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 18 | 413 (1)| 00:00:05 |
| 1 | SORT AGGREGATE | | 1 | 18 | | |
|* 2 | TABLE ACCESS FULL| BIG_TABLE | 20046 | 352K| 413 (1)| 00:00:05 |
--------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
2 - filter("ID"<=40000 AND "ID">=20000)
Statistics
----------------------------------------------------------
0 recursive calls
0 db block gets
1486 consistent gets
1484 physical reads
0 redo size
427 bytes sent via SQL*Net to client
349 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
1 rows processed
--????????????β????е?consistent gets??physical reads
c?????????30%?????е?????
scott@ORA11G> alter system flush buffer_cache;
scott@ORA11G> select sum(object_id)??avg(object_id) from big_table where id between 20000 and 50000;
Execution Plan
----------------------------------------------------------
Plan hash value: 599409829 --->???????????????????30%???????????????????????
--------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
--------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 18 | 413 (1)| 00:00:05 |
| 1 | SORT AGGREGATE | | 1 | 18 | | |
|* 2 | TABLE ACCESS FULL| BIG_TABLE | 30012 | 527K| 413 (1)| 00:00:05 |
--------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
2 - filter("ID"<=50000 AND "ID">=20000)
Statistics
----------------------------------------------------------
0 recursive calls
0 db block gets
1486 consistent gets
1484 physical reads
0 redo size
427 bytes sent via SQL*Net to client
349 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
1 rows processed
--?????????????????????????????
scott@ORA11G> alter system flush buffer_cache;
scott@ORA11G> select /*+ index(big_table big_table_pk) */ sum(object_id)??avg(object_id)
2 from big_table where id between 20000 and 50000;
Execution Plan
----------------------------------------------------------
Plan hash value: 3098837282
---------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
---------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 18 | 511 (1)| 00:00:07 |
| 1 | SORT AGGREGATE | | 1 | 18 | | |
| 2 | TABLE ACCESS BY INDEX ROWID| BIG_TABLE | 30012 | 527K| 511 (1)| 00:00:07 |
|* 3 | INDEX RANGE SCAN | BIG_TABLE_PK | 30012 | | 64 (0)| 00:00:01 |
---------------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
3 - access("ID">=20000 AND "ID"<=50000)
Statistics
----------------------------------------------------------
0 recursive calls
0 db block gets
526 consistent gets
526 physical reads
0 redo size
427 bytes sent via SQL*Net to client
349 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
1 rows processed
--????????β???????????????????????
--????????????????????????????????????????????????30%???Oracle ???????????????
--?????????????????????????????????30%?????Σ???????????????????????????????Ч?????????????Ч??
--????????????????????????????80%????????????????????????????ж?????
--???????????????????????????????????????????????????????￡?????????????裬??????????????????Ч??
--???
--????????????????????????????????????????????????????????o??????
--??Σ????????????????????????????粻???????????????????????
--????????????????????????????н????????????в???????????в?????sum(object_id)
??????
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