32个字节限制——Oracle直方图优化(二)

2014-11-24 18:59:49 · 作者: · 浏览: 82
ed.


SQL> SELECT CONTENTS ,COUNT(1) FROM T GROUP BY CONTENTS ORDER BY 1;


CONTENTS COUNT(1)
-------------------------------------------------- ----------
*******************************CONSUMER GROUP 2
*******************************eva lUATION CONTEXT 1
*******************************FUNCTION 60
*******************************INDEX 34
*******************************INDEX PARTITION 347
*******************************INDEX SUBPARTITION 3328
*******************************JOB CLASS 1
*******************************LIBRARY 3
*******************************OPERATOR 15
*******************************PACKAGE 164
*******************************PACKAGE BODY 13
*******************************PROCEDURE 11
*******************************SCHEDULE 1
*******************************SEQUENCE 1
*******************************SYNONYM 2552
*******************************TABLE 37
*******************************TABLE PARTITION 25
*******************************TABLE SUBPARTITION 1714
*******************************TYPE 538
*******************************VIEW 1150
*******************************WINDOW 2
*******************************WINDOW GROUP 1


SQL> SELECT SUBSTR(CONTENTS,1,32),COUNT(1) FROM T GROUP BY SUBSTR(CONTENTS,1,32);


SUBSTR(CONTENTS,1,32) COUNT(1)
---------------------------------------- ----------
*******************************E 1
*******************************J 1
*******************************P 188
*******************************C 2
*******************************S 2554
*******************************T 2314
*******************************F 60
*******************************O 15
*******************************L 3
*******************************W 3
*******************************I 3709
*******************************V 1150


12 rows selected.




SQL> SET AUTOT TRACEONLY EXP
SQL> SELECT * FROM T WHERE CONTENTS='*******************************TABLE';


Execution Plan
----------------------------------------------------------
Plan hash value: 2153619298


--------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
--------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 2314 | 149K| 24 (0)| 00:00:01 |
|* 1 | TABLE ACCESS FULL| T | 2314 | 149K| 24 (0)| 00:00:01 |
--------------------------------------------------------------------------


Predicate Information (identified by operation id):
---------------------------------------------------


1 - filter("CONTENTS"='*********