index range scan 单块读

--1719

SESSION_ID	1141	
SQL_ID	drpk7cccd9xhm	
MACHINE	WORKGROUPTLCB-PC	
BLOCKING_SESSION		
SAMPLE_TIME	10-4月 -19 07.50.01.154 下午	
MODULE	PL/SQL Developer	
PROGRAM	plsqldev.exe	
EVENT	db file sequential read	
P1	4	
P1TEXT	file#	
P2	190469	
P2TEXT	block#	
P3	1	
P3TEXT	blocks	
SQL_TEXT	select count(*) from p800 where owner='SCOTT' 	



SQL> select owner,segment_name,segment_type,partition_name from dba_extents where file_id=4 and 190469  between block_id and block_id+blocks-1;

OWNER	   SEGMENT_NAME 		  SEGMENT_TYPE			 PARTITION_NAME
---------- ------------------------------ ------------------------------ ------------------------------------------------------------------------------------------
TEST	   P800_IDX2			  INDEX


SQL> explain plan for select count(*) from p800 where owner='SCOTT' 	;

已解释。

SQL> select * from table(dbms_xplan.display());

PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Plan hash value: 3042126352

-------------------------------------------------------------------------------
| Id  | Operation	  | Name      | Rows  | Bytes | Cost (%CPU)| Time     |
-------------------------------------------------------------------------------
|   0 | SELECT STATEMENT  |	      |     1 |    17 |     5	(0)| 00:00:01 |
|   1 |  SORT AGGREGATE   |	      |     1 |    17 | 	   |	      |
|*  2 |   INDEX RANGE SCAN| P800_IDX2 |   874 | 14858 |     5	(0)| 00:00:01 |
-------------------------------------------------------------------------------

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

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

Note
-----
   - dynamic sampling used for this statement (level=2)

已选择18行。