「なぜ、あのSQLは遅いのか」を正しく的確に調査する方法：しばちょう先生の試して納得！　DBAへの道（改）（2）（2/3 ページ）

$ sqlplus TRY/TRY12345
SQL> 
explain plan for
select * from TBL2 where col1 = 10000;
　
解析されました。
　
SQL> @?/rdbms/admin/utlxpls
　
PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------------------
Plan hash value: 1207070705
　
--------------------------------------------------------------------------------------------
| Id  | Operation                   | Name         | Rows  | Bytes | Cost (%CPU)| Time     |
--------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT            |              |     1 |    65 |     3   (0)| 00:00:01 |
|   1 |  TABLE ACCESS BY INDEX ROWID| TBL2         |     1 |    65 |     3   (0)| 00:00:01 |
|*  2 |   INDEX UNIQUE SCAN         | PK_TBL2_COL1 |     1 |       |     2   (0)| 00:00:01 |
--------------------------------------------------------------------------------------------
　
Predicate Information (identified by operation id):
---------------------------------------------------
　
   2 - access("COL1"=10000)
　

sqlplus /nolog
SQL>
connect / as sysdba
alter system FLUSH BUFFER_CACHE;
　
connect TRY/TRY
set timing on
select count(*) from TBL2;
　
  COUNT(*)
----------
   1000000
　
経過: 00:00:02.61
　
　
connect / as sysdba
alter system FLUSH BUFFER_CACHE;
　
connect TRY/TRY
set timing on
select count(*) from TBL3;
　
  COUNT(*)
----------
   1000000
　
経過: 00:00:10.58